Rate Of Increase In Surface Area Research Articles

Regional morphodynamics of supraglacial lakes in the Everest Himalaya

Reduction of ice masses concerning global warming is significantly changing geomorphology in high mountains. Formation of supraglacial lakes is one of such essential indications. Therefore, in the present study, we attempted to understand regional morphodynamics of supraglacial lakes, distributed in 17 glaciers within the Everest Himalaya. An average of 0.08 km2/yr lake expansion rate was noticed during the studied year. Decadal (2010–2019) lake morphodynamic study using high resolution satellite images revealed that only 161 out of total 2424 lakes were static, and mostly concentrated at the lower part of the ablation area with an alarming rate of surface area increase. We also found appearance of new cluster of lakes at higher elevations. We collected here statistical evidences of regional morphodynamics and key controlling factors to stabilize lakes. The parameters, viz., spatio-temporal distribution of lakes, their domain wise variation, multi-temporal (Seasonal to long-term) changes, lake density, and stability index were estimated and mapped. Finally, we concluded that new lake formations at higher elevation were triggered by gradual increase in temperature, decrease in glacier surface velocity, slope and ice thickness. The feature selection techniques indicated ice thickness as prior controlling factor followed by the surface velocity and slope to stabilize lakes at the lower part of ablation.

Flame-Surface Advection in Transient Periodic Flow

The advection of an interface by a known transient periodic excitation flow is investigated in the present study, the results of which are relevant to the propagation of nearly isothermal premixed flames in turbulent flow. The relation between the corrugated-surface area and the intensity of the excitation flow is obtained numerically and compared with exact analytically derived solutions. The results elucidate the relation between the surface area and the intensity of spatial and temporal flow-field variations at low, moderate, and large intensities and highlight the stabilizing influence of Huygens surface propagation (e.g., of premixed flames) on the rate of surface-area increase, which is found to be otherwise unbounded in time.

Increase in the specific surface area of budesonide during storage postmicronization.

To evaluate an anomalous increase in the specific surface area of budesonide during storage postmicronization. Budesonide was micronized using a conventional air-jet mill. Surface areas and total pore volumes were measured using nitrogen sorption. Porosity was measured using mercury intrusion porosimetry. Particle size was measured using laser diffraction. Budesonide exhibited a surface area increase of 22 +/- 2% when stored at 25 degrees C following micronization. The rate of surface area increase was lower at 20 degrees C. suggesting a temperature-dependent stress relaxation mechanism for the micronized particles. The increase in surface area was accompanied by: (a) an increase in total pore volume: (b) a shift of the pore size distribution to smaller pore sizes; (c) a decrease in size of particles above approximately 1 microm; and (d) an increase in rugosity/surface roughness. Freshly micronized budesonide exhibited an unusual and significant postmicronization increase in specific surface area upon storage under ambient conditions. Postmicronization stress-relief by intraparticle crack formation, crack propagation with time, and particle fracture seems to be the primary mechanism behind this surface area increase.

Spectrin-phospholipid interaction: A monolayer study

1. (1) The interaction of synthetic and natural phospholipids with spectrin, purified from human erythrocyte membranes, was studied using the monolayer technique at constant surface pressure. Spectrin penetration into the lipid monolayer was recorded as the rate of surface area increase on a two-compartment trough. 2. (2) High spectrin penetration rates were observed with negatively charged phospholipids while zwitterionic or neutral lipids showed only poor spectrin affinity. This penetration rate was strongly affected by the subphase pH. At pH 5.5, maximal pentration rates were observed for phosphatidylglycerol and phosphatidylserine but not for phosphatidylcholine. 3. (3) In comparing the penetration rates for phospholipids with a natural fatty acid composition and the dimyristoyl species of phosphatidic acid, phosphatidylglycerol, phosphatidylserine and phosphatidylcholine, the lipid fatty acid composition proved to be an important parameter. The differences are correlated with the area per lipid molecule. 4. (4) Other parameters affecting the area per lipid molecule such as surface pressure, pH and salt concentration also strongly influenced spectrin penetration rates for negatively charged phospholipids. Spectrin penetration into phosphatidylcholine monolayers is only slightly affected by variation of these conditions. 5. (5) The effect of Ca 2+ on spectrin-lipid interactions was studied for several phosphatidylglycerol and phosphatidylserine species. Both lipids condensed upon the addition of Ca 2+, but only in the case of the phosphatidylserine was this accompanied by extrusion of the spectrin from the interface, which is in agreement with earlier calorimetric experiments with bilayer systems of analogous composition (Mombers, C., Verkleij, A.J., de Gier, J. and van Deenen, L.L.M. (1979) Biochim. Biophys. Acta 551, 271–281). For this phenomenon a model is presented.