Surface Pressure Difference Research Articles

Dynamic Interfacial Properties of Surface-excess Films of Phospholipids and Phosphonolipid Analogs

Dynamic respreading and maximum surface pressures are analyzed as a function of chain-backbone linkage, phosphatephosphonate group, and N-headgroup structure for surface-excess films of dipalmitoyl phosphatidylcholine (DPPC), dipalmitoyl phosphatidylethanolamine (DPPE), and 13 related phospholipid and phosphonolipid analogs. Film behavior varied significantly with molecular structure, related in part to differences in molecular packing and mobility from ether vs amide vs ester linkages, as well as structure-induced variations in headgroup charge, hydration, hydrophobicity, hydrogen bonding, and steric bulk. Analysis of surface pressure-area isotherms from Wilhelmy balance experiments at three different pH values (H. Liu et al., J. Colloid Interface Sci. 167, 378-390) showed that: (1) diether phosphonolipid (DEPN) analog compounds had better respreading on successive cycles into the collapse regime compared to ether-amide phosphonolipid (EAPN) analogs with equivalent N-headgroups at pH 2.6, 5.6, and 11.5; (2) diether phospholipids (DHPC and DHPE) also had better respreading than corresponding diester phospholipids (DPPC and DPPE) at all three pH values; (3) the headgroup phosphonate vs phosphate linkage led to decreased cycle 2/cycle 1 respreading at all pH in the ethanolamine diether phosphonolipid DEPN-13 vs DHPE and in the choline diether phosphonolipid DEPN-8 vs DHPC, although cycle 7/cycle 1 respreading was improved in DEPN-8; (4) maximum surface pressures generated by PC-related compounds (DPPC, DHPC, DEPN-8, EAPN-9) were > 70 mN/m independent of pH, while maximum pressures for PE-related compounds (DPPE, DHPE, DEPN-13, EAPN-13) were lower at 51-67 mN/m and varied more with pH; (5) respreading and maximum surface pressures did not vary in a consistent pattern as a function of pH for DEPN and EAPN analogs with different degrees of N-methylation, particularly at pH 11.5 where DEPN-10 and EAPN-110 with two N-methyl groups paradoxically had the lowest maximum surface pressures and best respreading of any compounds studied; and (6) the N-substitution of two hydroxyethyl groups for two methyl groups had less effect on surface behavior than N-substitution of methyl groups for hydrogen. The significant differences in dynamic respreading and maximum surface pressure found here for relatively small changes in molecular structure and headgroup charge indicate that specific compositional requirements likely exist for glycerophospholipids in functional pulmonary surfactant. The results also support the feasibility of synthesizing phospholipid-like molecules with specific surface-active properties for potential use in new exogenous lung surfactant mixtures.

中部日本における地衡風と地上のベクトル平均風との関係

An attempt was made to survey the angle of deflection between the surface wind vector (Vs)-the vector mean wind over central Japan, obtained by vectorially averaging the surface wind values at 270 AMeDAS stations-and the geostrophic wind vector (Vg) directly calculated from the surface pressure differences among four stations around central Japan.The value of the mean deflection angle between the two directions was 76 degrees (from Vg to Vs, measured counterclockwise), a relatively large value compared with other studies. The critical direction of Vg, at which the deflection angle significantly changed, was found to occur around ENE. To investigate this critical direction, an attempt was made to relate the angle to surface airflow patterns. It was concluded that the critical direction corresponded to a significant direction of Vg which divides the surface airflow pattern into two categories: the airflow patterns with prevailing NW winds and with prevailing NE winds over the surface of the Kanto plain.The angle of deflection and the wind speed ratio υs/υg were discussed and compared with the results of previous studies.

On the relationship between the 10.7 cm solar flux, surface pressure and air temperature over Greece

The behaviour of the 10.7 cm solar flux, surface air temperature and sea surface pressure are discussed on the basis of the 11-year solar cycle and the Quasi-Biennial Oscillation (QBO) over Greece. In this respect a strong negative correlation was identified between the 11-year solar cycle and the sea surface pressure during the winter west phase years of the QBO, while a similar correlation was found between the sea surface pressure differences estimated between stations located in northern and southern regions of Greece, and the 11-year solar cycle. On the contrary, for the same QBO period, a strong positive correlation was observed between the 11-year cycle and the surface air temperature in Greece in agreement with recently published results. Considering the east phase QBO years, no correlation was identified between the 10.7 cm solar flux and the sea surface pressure and surface air temperature over Greece.

Binding of pancreatic carboxylester lipase to mixed lipid films. Implications for surface organization.

The hydrolysis of ester substrates in mixed monolayers with 1-palmitoyl-2-oleoylphosphatidylcholine by pancreatic carboxylester lipase (CEL) shows an abrupt increase from less than 10 to 100% when substrate abundance exceeds a critical value (Tsujita, T., Muderhwa, J.M., and Brockman, H.L. (1989) J. Biol. Chem. 264, 8612-8618). Adsorption of native CEL to these mixed lipid films under the same conditions shows a monotonic increase with substrate abundance to a maximum of approximately 4 pmol/cm2. In the range of low substrate hydrolysis, bound enzyme reaches 0.6 pmol/cm2 or about one-sixth of an enzyme monolayer. Given the high turnover number of the enzyme, absence of bound catalyst cannot explain the lack of substrate hydrolysis. Similarities of the adsorption data obtained with different substrates suggest a common, area-based mechanism with an excluded area for the phospholipid. Quantitative analysis confirms this and gives an excluded area of 43.5 +/- 1.0 A2/molecule. Comparable studies with the hydrolysis product, oleic acid, replacing each substrate show markedly different results. Up to oleic acid mol fractions of 0.5, bound CEL levels are essentially constant at 0.215 pmol/cm2. This behavior relative to substrate-containing films cannot be ascribed to differences in surface pressure, surface potential, monolayer compressibility, nonexcluded area, CEL denaturation, or oleic acid charge. Together with the ultrasensitive composition dependence of substrate hydrolysis, the data suggest that phospholipid-based organization of the surface is a primary regulator of enzyme binding and catalysis.

Pleural liquid pressure at the caudal border of the lung

Model simulation indicates that pressure recorded through a capsule, when lung border is under it, is essentially equal to pressure of pleural liquid (Pliq) surrounding lung border, though only a strip of capsule membrane is exposed to this liquid (the rest is facing diaphragm and lung). At the top of the right 8th or 9th intercostal space of dogs in left lateral posture Pliq recorded through a capsule at transit of lung border during inspiration (bor.I) or expiration (bor.E) was −19.7 ± 1.1 and −11.2 ± 0.3 cm H 2O, respectively. Pliq recorded simultaneously through a cannula on the flat surface of lung in 5th or 6th intercostal space (corrected for 1 cm lower height) was −18.7 ± 1.4 and −12.4 ± 0.8 cm H 2O. Similar values of Pliq on lung border and on flat surface of lung, despite different kinds of deformation and different measuring devices, provide further evidence that Pliq is more subatmospheric than pleural surface pressure. Seventy percent of difference in Pliq between bor.I and bor.E was accounted for by: (a) corresponding difference in pleural surface pressure, and (b) greater tidal change of liquid than surface pressure. Possible factors accounting for the remaining 30% are discussed.

Melittin and the 8–26 fragment. Differences in ionophoric properties as measured by monolayer method

Melittin is a major (approximately 50%) protein component of bee venom. This peptide is an amphiphilic protein, because, while the amino acid residues 1-20 are predominantly hydrophobic (with the exception of Lys-7), residues 21-26 are hydrophilic. The binding properties to vesicles and lipid bilayers of melittin have provided much useful information regarding biological (hemolytic) activity (Habermann, E., 1972, Science [Wash. DC], 177:314-322). Recent studies have convincingly established that the melittin monolayer (at air-water interface) model membrane system allows one to analyze the various forces present in such structures. We present comparative monolayer studies of melittin and the peptide fragment 8-26 regarding the channel formation for the selective anion (Cl-) penetration in monolayers, analogous to melittin (tetramer) channel function in lipid bilayer. The differences in surface pressure and surface potential of monolayers between native melittin and the 8-26 fragment suggest that these may be ascribed to Lys-7.

Heavy-ion fusion: Effect of entrance channel mass asymmetry

When two bubbles are connected by a window, the larger bubble grows at the expense of the smaller, due to the surface pressure difference.

Selective removal of lipids from the outer membrane layer of human erythrocytes without hemolysis. Consequences for bilayer stability and cell shape

(1) Treatment of erythrocytes with phospholipase A 2 from bee venom cleaves about 55% of the phosphatidylcholine in the outer membrane lipid layer without changing the discoid shape of the cells. All of the fatty acids and 80% of the lysophosphatidylcholine produced under this conditions can be sequentially extracted by bovine serum albumin without hemolysis of the cells. (2) The cells remain discoid up to extraction of all of the fatty acids and 15% of the lysophosphatidylcholine. Removal of a higher fraction of lysophosphatidylcholine induces formation of stomatocytes and sphero-stomatocytes, probably going along with an internalization of membrane vesicles. Stomatocytosis can be explained on the basis of the ‘bilayer couple hypothesis’ (Sheetz, M.P. and Singer, S.J. (1974) Proc. Natl. Acad. Sci. 71, 4457–4461). The shape change will compensate for the differences in surface pressure between the two leaflets induced by selective removal of material from the outer leaf of the bilayer. (3) Increasing the shear modulus of the membrane by diamide prevents this compensatory shape change even after extraction of up to 80% of the lysophosphatidylcholine, which amounts to a loss of 34% of the phospholipids of the outer membrane layer or 22% of its area. This leads to the interesting situation of a membrane possibly having a strikingly diminished ratio of the numbers of phospholipid molecules in the outer to that in the inner lipid layer. A marked difference in surface pressures should arise in this situation, unless other compensatory mechanisms become operative. Evidence for a compensation for outer lipid loss by a constriction of the inner layer has been obtained. A compensation by transbilayer reorientation of phospholipids could not be demonstrated. This latter observation supports the concept of a stabilisation of the asymmetric phospholipid arrangement by proteins such as spectrin.

Meteorological forcing of coastal waters by the inverse barometer effect

Water level and surface pressure data from the northeastern and northwestern Gulf of Mexico are used to investigate the water level response to meteorological forcing by the inverse barometer effect. Statistically significant coherence-squared values are computed for variations in cross-Gulf surface pressure and water level differences over time scales on the order of 2 to 6 days. Water level variations of approximately ±4–5 cm are postulated for the northern Gulf of Mexico in response to surface pressure differences. Meteorological forcing by the inverse barometer effect appears to be significantly greater in the winter months, when cross-Gulf air pressure differences of up to ±20 mb are recorded.

Arctic Sea-Ice Conditions in Early Spring Viewed by Satellite

A detailed analysis was made of satellite imagery, mainly from the NOAA-VHRR (National Oceanic and Atmospheric Administration-Very High Resolution Radiometer) in the visible and infrared range, to produce maps of mean monthly ice concentration of the western Arctic Ocean for March 1973 and March 1974. Using multidaily coverage of the saetllite, a total of 2552 data points divided into 47 subsections of the Arctic Ocean were analyzed. In both years an average of 75% of usable observations were obtained; the cloudy observations constituted 25%. The highest ice concentrations found in the Beaufort Sea and East Siberian Sea were 85% and 81%, respectively for March 1973. For March 1974, the ice concentration was on an average 10% higher due to a greater frequency of onshore wind components as reduced from 5-day means of surface pressure differences between selected coastal stations of the Beaufort Sea. Areas of low ice concentration were found in parts of the northern Bering Sea, along the northwest coast of Alaska and northwest of Wrangel Island in both years. In 1973 low ice concentrations were also observed north of the New Siberian Islands and west of Banks Island.

Long term variations in western tropical Pacific cyclogenesis associated with the Southern Oscillation

THE ‘Southern Oscillation’, as statistically defined by Sir Gilbert Walker, is the barometrically recorded exchange of air mass in tropical latitudes around the complete circumference of the globe1,2. Indices of Southern Oscillation based on the surface pressure differences between the Indonesian equatorial low (measured at Darwin, Australia) and the South Pacific subtropical high (considered the Southern Oscillation's eastern core and measured at Easter Island) have been used by Quinn3–5, who relates fluctuations in these indices to anomalous equatorial rainfall and occurrences of ‘El Nino’, (the accumulation of anomalously warm water in the eastern tropical Pacific). In this paper, we use 12-month running means of monthly mean surface pressures over three areas across the northern tropical Pacific as an index of the Southern Oscillation index, and we find that pressure convergences in this index are associated with years of relatively low numbers of western Pacific tropical cyclones.

Spectroscopic determination of surface pressure and elevation differences on Mars

Observations of a carbon dioxide band at 1.2206 μ (8192.6 cm−1) made at the opposition of Mars in June, 1969, are used with laboratory data to derive a value for the pressure at the surface of Mars. This band is especially suitable because it is sensitive to pressure, lying in the transition region of the curve of growth, but is relatively free of telluric contamination. The pressure derived is , corresponding to the Martian desert region Amazonis.Using a five-channel spectrometer, the strengths of two carbon dioxide bands at 1.5753 and 1.6057 μ (6347.8 and 6227.9 cm−1) were compared over a Martian dark area (Mare Acidalium) and a nearby bright area in Amazonis. The bands were 1.32 times stronger in the dark area than in the bright area. Interpreting this as evidence for elevation differences on the Martian surface, it is found that the dark Mare Acidalium is 2.5 km lower in elevation than the bright area with which it was compared.

Forecasting of rainfall of 30 mm or more over Bombay

The graphical integration technique of Brier has been employed in evolving an objective method for predicting the occurrence of rainfall of 30 mm or more m 24 hours over Bombay and Thana Districts in the subsequent 24 hours, during July-August. Easily determinable variables-(l) 700-mb contour height difference between Calcutta and Visakhapatnam, (2) 850-mb contour height difference between Nagpur and Delhi (3) surface pressure difference between Vengurla and Baroda and (4) precipitable water over Bombay, have been utilized in evolving this technique. Data for the months of July and August for 1957-1961 have been used as basic data and corresponding ones for 1962 as the test data. The method gave correct forecasts of rainfall >=30 mm on 70 per cent occasions.

High-Dispersion Spectroscopic Obervations of Mars. I. The CO_{2} Content and Surface Pressure

view Abstract Citations (21) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High-Dispersion Spectroscopic Obervations of Mars. I. The CO_{2} Content and Surface Pressure Spinrad, Hyron ; Schorn, Ronald A. ; Moore, Roger ; Giver, L. P. ; Smith, Harlan J. Abstract From high-dispersion infrared McDonald and Lick Observatories' spectrograms of Mars we have determined a CO2 abundance of 90 + 27 (estimated error) m-atm (STP) at 200 K, chosen as a representative lower-atmosphere temperature. We used the weak 5P3 CO2 lines near X 8700 A. An abundance of 90 m-atm of CO2 gives a surface partial pressure of 6.6 mb. The observation and reductions are discussed. By comparing our weak-line CO2 abundance with Sin ton's and Kuiper's measures of the saturated 1.6- and 2.0- bands we find a total surface pressure of P, = 8 1 4 (estimated error) mb from the 1.6- band and P, =1618mb from the 2.0- band. The technique of analysis follows Kaplan, Mllnch, and Spinrad and Owen and Kuiper. The lower pressure (1.6- data) is to be preferred. A compromise value is P, = 10__+10 mb. The result is compared to the Mariner IV occultation data which yield P, = S or 6 mb if the temperature of the lower Martian atmosphere is 180 K. The difference in surface pressure is not substantial; the occultation results coupled with our CO2 abundance suggest an almost pure CO2 atmosphere for Mars. Publication: The Astrophysical Journal Pub Date: November 1966 DOI: 10.1086/148897 Bibcode: 1966ApJ...146..331S full text sources ADS | Related Materials (1) Part 2: 1967ApJ...147..743S