Changes In Surface Pressure Research Articles

Study of seasonal and long-term vertical deformation in Nepal based on GPS and GRACE observations

Lithospheric deformation signal can be detected by combining data from continuous global positioning system (CGPS) and satellite observations from the Gravity Recovery and Climate Experiment (GRACE). In this paper, we use 2.5- to 19-year-long time series from 35 CGPS stations to estimate vertical deformation rates in Nepal, which is located in the southern side of the Himalaya. GPS results were compared with GRACE observations. Principal component analysis was conducted to decompose the time series into three-dimensional principal components (PCs) and spatial eigenvectors. The top three high-order PCs were calculated to correct common mode errors. Both GPS and GRACE observations showed significant seasonal variations. The observed seasonal GPS vertical variations are in good agreement with those from the GRACE-derived results, particularly for changes in surface pressure, non-tidal oceanic mass loading, and hydrologic loading. The GPS-observed rates of vertical deformation obtained for the region suggest both tectonic impact and mass decrease. The rates of vertical crustal deformation were estimated by removing the GRACE-derived hydrological vertical rates from the GPS measurements. Most of the sites located in the southern part of the Main Himalayan Thrust subsided, whereas the northern part mostly showed an uplift. These results may contribute to the understanding of secular vertical crustal deformation in Nepal.

A twentieth century perspective on summer Antarctic pressure change and variability and contributions from tropical SSTs and ozone depletion

AbstractDuring the late twentieth century, the Antarctic atmospheric circulation has changed and significantly influenced the overall Antarctic climate, through processes including a poleward shift of the circumpolar westerlies. However, little is known about the full spatial pattern of atmospheric pressure over the Antarctic continent prior to 1979. Here we investigate surface pressure changes across the entire Antarctic continent back to 1905 by developing a new summer pressure reconstruction poleward of 60°S. We find that only across East Antarctica are the recent pressures significantly lower than pressures in the early twentieth century; we also discern periods of significant positive pressure trends in the early twentieth century across the coastal South Atlantic sector of Antarctica. Climate model simulations reveal that both tropical sea surface temperature variability and other radiative forcing mechanisms, in addition to ozone depletion, have played an important role in forcing the recent observed negative trends.

Identifying the selectivity of antimicrobial peptides to cell membranes by sum frequency generation spectroscopy.

Cationic amphiphilic peptides have been engineered to target both Gram-positive and Gram-negative bacteria while avoiding damage to other cell types. However, the exact mechanism of how these peptides target, bind, and disrupt bacterial cell membranes is not understood. One specific peptide that has been engineered to selectively capture bacteria is WLBU2 (sequence: RRWVRRVRRWVRRVVRVVRRWVRR). It has been suggested that WLBU2 activity stems from the fact that when interacting with bacterial cell membranes the peptide assumes an α-helical structure and inserts itself into the membrane. Alternatively, in the presence of mammalian cell membranes, the peptide assumes an inert β-sheet structure. To test this hypothesis, the authors applied sum frequency generation (SFG) spectroscopy and surface tensiometry to identify the structure of WLBU2 as it interacts with model lipid monolayers that mimic mammalian and bacterial cell membranes. Model mammalian cell membranes were built upon zwitterionic 1,2-dipalmitoyl-sn-glycero-3-phosphocholine lipids while bacterial cell membranes were constructed with negatively charged 1,2-dimyristoyl-sn-glycero-3-phospho-(1'-rac-glycerol) lipids. Observed changes in surface pressure at the peptide-lipid-air interface demonstrate that the peptide has a clear binding preference toward negatively charged bacteria-like lipids. The structure of both the lipids and peptides were characterized by SFG spectra collected at the monolayer interface. Changes in monolayer structure as the peptide binds were observed by tracking the intensities of SFG vibrational modes related to the acyl chains within the lipids. Peptide structures when bound to both types of lipids were determined by SFG spectra collected within the amide I vibrational band. The SFG spectra of WLBU2 interacting with the model mammalian lipid monolayer contain two peaks near 1642 and 1678 cm-1 indicative of an inactive β-sheet structure. SFG spectra collected from the peptide bound to a bacteria-like lipid monolayer contains just a single peak near 1651 cm-1 which corresponds to an active α-helix structure. Combined, the tensiometry and SFG results demonstrate that WLBU2 both possesses a higher binding affinity toward and is in an active α-helix structure when bound to bacterial cell membranes.

Effects of long-duration sitting with limited space on discomfort, body flexibility, and surface pressure

The objective of this work is to analyze the effect of long-duration sitting on a seat with the limited space on discomfort, body flexibility and surface pressure, and the changes of discomfort, surface pressure and body flexibility with the sitting time. The experiment was that eighteen healthy subjects seated for long-duration (3 h) in three different seat pitches (32 inches, 30 inches and 28 inches) conditions in the laboratory. The discomfort, pressure, and body flexibility parameters have been measured during the experiments. Comparing the data between three seat conditions during the sitting time, the results show that there is a significant difference in the overall discomfort ratings and pressure variances between three different seat conditions after 3 h, and significant effects were found among the three different seat pitches for the discomfort rating of shoulder, middle back and low back after 3 h. No significant findings were seen in lumbar and hamstring flexibility. The relationship between subjective ratings and objective measurements has been analyzed with spearman analysis. The correlation analysis suggest that differences in arm and middle back discomfort were significantly negatively correlated to Sit-Reach(3) scores (Correlation Coefficients: 0.492 and −0.527; p values of 0.038 and 0.025, respectively). Differences in overall discomfort, thigh and knee were significantly correlated to average pressure (Correlation Coefficients: 0.562, 0.833 and 0.520; p values of 0.004, 0.001.and 0.027, respectively).Relevance to industry Nowadays many forms of public transport, especially prolonged flight, involve sitting in the seat with a confined sitting space for long time, which may have bad effects on the user's flexibility and discomfort perception. The survey of passenger's subjective perception for different seat pitches and their physiological changes is helpful to find a relationship between subjective perception and objective measurement and understand how seat pitch to influence the discomfort, and the result can provide a reference for determining the appropriate distance of seat pitch.

Climate projections of spatial variations in coastal storm surges along the Gulf of Mexico and U.S. east coast

Using statistically downscaled atmospheric forcing, we performed a numerical investigation to evaluate future climate’s impact on storm surges along the Gulf of Mexico and U.S. east coast. The focus is on the impact of climatic changes in wind pattern and surface pressure while neglecting sea level rise and other factors. We adapted the regional ocean model system (ROMS) to the study region with a mesh grid size of 7–10 km in horizontal and 18 vertical layers. The model was validated by a hindcast of the coastal sea levels in the winter of 2008. Model’s robustness was confirmed by the good agreement between model-simulated and observed sea levels at 37 tidal gages. Two 10-year forecasts, one for the IPCC Pre-Industry (PI) and the other for the A1FI scenario, were conducted. The differences in model-simulated surge heights under the two climate scenarios were analyzed. We identified three types of responses in extreme surge heights to future climate: a clear decrease in Middle Atlantic Bight, an increase in the western Gulf of Mexico, and non-significant response for the remaining area. Such spatial pattern is also consistent with previous projections of sea surface winds and ocean wave heights.

Aerodynamical and Structural Analysis of Operationally Used Turbine Blades

This paper presents an integrated methodology for the analysis of operationally-used turbine blades, incorporating aerodynamic and multiple structural simulations. In jet engines, blade rubbing and erosion lead to deviations of the blade geometry. The presented functional simulations are conducted in order to predict the influence of wear on the performance of turbine blades based on these geometric variations.A numerical simulation of the investigated turbine blades using CFD show the change of aerodynamic performance and the flow field due to wear. Additionally, the deviations of the blade geometry lead to a different pressure and temperature distribution on the blade surface, which is used as input for the structural simulations.The change in geometry, surface pressure and temperature lead to a change in vibration behavior of the blade. Particularly the eigenfrequencies and excitation are affected. This is incorporated into the analysis by performing a structural vibration simulation of a complete bladed disk, using component mode synthesis and wave base substructuring. The mistuning effects are analyzed statistically using the Monte Carlo method.The change in vibration amplitudes influences crack opening and closing for a single blade under thermo-mechanical load. These processes, including thermal expansion, are investigated using the extended finite element method. Two real turbine blades are used to compare the characteristics of a new and a used blade.

Transformation Mechanism of Dual-mode Penetrators Achieved by Changing of Single-point Detonation

<p>A shaped charge was produced with a wave shaper that can transform dual-mode penetrators by changing the single-point detonation location. Specifically, the theory of denotation wave formation was applied to analyze changes in the liner surface pressure in different initiation situations. An analytical model was established of the projectile explosively formed by denotation at the top of the liner and jetting projectile charge formed by denotation at the center of charge. LS-DYNA finite element simulation software was used to study the effects of the liner configuration parameters on the formation of dual-mode penetrators, and orthogonal optimizing design and simulation calculation was conducted to obtain suitable structural parameters of a uniform-thickness eccentric hemisphere liner. X-ray imaging and penetration experiments were then conducted. The penetration depth of the explosively formed projectile in a steel target was 0.64<em>D</em><sub>k</sub>（the charge diameter）,while that of the jetting projectile charge was 2.42<em>D</em><sub>k</sub> when the burst height was approximately 13<em>D</em><sub>k</sub>.</p>

Boundary layer characterization and acoustic measurements of flow-aligned trailing edge serrations

Trailing edge serrations designed to reduce airfoil self-noise are retrofitted on a NACA 0018 airfoil. An investigation of the boundary layer flow statistical properties is performed using time-resolved stereoscopic PIV. Three streamwise locations over the edge of the serrations are compared. An analysis of the results indicates that, while there is no upstream effect, the flow experiences significant changes as it convects over the serrations and toward its edges. Among the most important, a reduced shear stress and modifications of the turbulence spectra suggest beneficial changes in the unsteady surface pressure that would result in a reduction of trailing edge noise. Microphone array measurements are additionally performed to confirm that noise reduction is indeed observed by the application of the chosen serration design over the unmodified airfoil.

Isoleucine/leucine residues at "a" and "d" positions of a heptad repeat sequence are crucial for the cytolytic activity of a short anticancer lytic peptide.

Many lytic peptides contain a heptad sequence with leucine or isoleucine residues at "a" and "d" positions. However, their roles in the peptide-induced cytolytic process remain unclear. We have recently reported an anticancer lytic peptide ZXR-2 (FKIGGFIKKLWRSLLA), which contains a shortened zipper-like sequence with Ile/Leu at "a" and "d" positions. To understand the roles of these Ile/Leu residues, a series of analogs were constructed by sequentially replacing the Ile or Leu residue with alanine (Ala). Significant reduction of the cytolytic activity was observed when the Ile (3rd and 7th) and Leu (10th and 14th) residues at the "a" and "d" positions were substituted, while the replacement of the separate Leu (15th) residue had less effect. Based on the quenching of the intrinsic fluorescence of the peptides and their induced surface pressure changes of lipid monolayer, it was conjectured that the peptide ZXR-2 might insert into cell membranes from the C-terminal and to a depth of the W11 position. Accordingly, I3, I7, and L10 residues which mainly exposed in aqueous solution were more responsible for the peptide self-association on cell membranes, while L14, together with L15, might help peptide insert and anchor to cell membranes. These results are significant to elucidate the crucial roles of such Ile/Leu residues at "a" and "d" positions in peptide-peptide and peptide-membrane interactions to exert the membrane disruption activity of lytic peptides. With further understanding about the structure-activity relationship of lytic peptides, it would be helpful for designing novel anticancer lytic peptides.

Measuring muscle activities during gym exercises with textile pressure mapping sensors

We present a wearable textile sensor system for monitoring muscle activity, leveraging surface pressure changes between the skin and compression garment. Our first prototype is based on an 8×16 element fabric resistive pressure mapping matrix with 1 cm spacial resolution and 50 fps refresh rate. We evaluate the prototype by monitoring leg muscles during realistic leg workouts in a gym out of the lab. The sensor covers the lower part of quadriceps of the user. The shape and movement of the two major muscles (vastus lateralis and medialis) are visible from the data visualizing during various exercises. With features extracted from spacial and temporal domains out of the pressure force mapping information, with 4 different leg exercises plus non-workout activities (relaxing, adjusting machines and walking), we have reached 81.7% average recognition accuracy on a fine-grain sliding window basis, 93.3% on an event basis, and 85.6% spotting F1-score. We further investigate the relationships between people’s perception of the exercise quality/difficulty and the variation and consistency of the force pattern. A second prototype is also developed with tether-free to explore various placements including upper-arm, chest and lower back; a brief comparison with arm-worn EMG shows our approach is comparable on the signal quality level.

Impact of anthropogenic aerosols from global, East Asian, and non-East Asian sources on East Asian summer monsoon system

The impact of the total effects due to anthropogenic aerosols from global, East Asian, and non-East Asian sources on East Asian summer monsoon (EASM) system is studied using an aerosol-climate online model BCC_AGCM2.0.1_CUACE/Aero. The results show that the summer mean net all-sky shortwave fluxes averaged over East Asian monsoon region (EAMR) at the top of the atmosphere (TOA) and surface reduce by 4.8 and 5.0Wm−2, respectively, due to the increases of global aerosol emissions in 2000 relative to 1850. Changes in radiations and their resulting changes in heat and water transport and cloud fraction contribute together to the surface cooling over EAMR in summer. The increases in global anthropogenic aerosols lead to a decrease of 2.1K in summer mean surface temperature and an increase of 0.4hPa in summer mean surface pressure averaged over EAMR, respectively. It is shown that the changes in surface temperature and pressure are significantly larger over land than ocean, thus decreasing the contrast of land-sea surface temperature and pressure. This results in the marked anomalies of north and northeast winds over eastern and southern China and the surrounding oceans in summer, thereby weakening the EASM. The summer mean precipitation averaged over the EAMR reduces by 12%. The changes in non-East Asian aerosol emissions play a more important role in inducing the changes of local temperature and pressure, and thus significantly exacerbate the weakness of the EASM circulation due to local aerosol changes. The weakening of circulation due to both is comparable, and even the effect of non-local aerosols is larger in individual regions. The changes of local and non-local aerosols contribute comparably to the reductions in precipitation over oceans, whereas cause opposite changes over eastern China. Our results highlight the importance of aerosol changes outside East Asia in the impact of the changes of anthropogenic aerosols on EASM.

Blade-Row Interaction Effects on Unsteady Stator Loading in an Embedded Compressor Stage

Blade-row interactions drive unsteady blade forces in compressors. This paper presents a perspective on understanding how the pitchwise variations in the flow at the exit of the rotor affect the surface pressures on the downstream vane. The rotor wakes and tip leakage flows are the primary unsteady flow features that drive unsteady lift on the vane. However, those rotor flow features are affected by their interaction with the wakes from upstream vanes. Thus, the interaction with stator 1 and rotor 2 must be understood to adequately characterize the interaction between rotor 2 and stator 2. This paper uses vane clocking, or the circumferential shift in successive vane rows of similar counts, to illuminate these blade-row interaction effects on the downstream vane surface pressure distribution. To accomplish this, experiments are performed in a three-stage axial compressor where high-frequency response pressure transducers are flush-mounted in the stator 2 pressure and suction surfaces are flush-mounted at 50 and 80% spans. Results show that rotor 1–rotor 2 interactions contribute significantly to the changes in unsteady stator surface pressure over the course of a rotor revolution. Also, the rotor 1–rotor 2 interaction levels change in the pitchwise direction downstream of the rotor; thus, the changes in surface pressure are affected by vane clocking. Furthermore, the rotor tip leakage flow is an additional contributor to the unsteady stator surface pressures measured at 80% span, providing an additional pressure peak per blade passing, and thus more high-frequency content (twice the blade-passing frequency).

Interaction of the Antimicrobial Peptides Rhesus θ-Defensin and Porcine Protegrin-1 with Anionic Phospholipid Monolayers.

A combination of Langmuir isotherm, Brewster angle microscopy (BAM), and neutron reflectivity studies have been performed to gain insight into the effects on model bacterial cell membranes of the antimicrobial peptides, Rhesus θ-defensin 1 (RTD-1), and porcine protegrin 1 (PG-1). The peptides were interacted with monolayers spread at the air-water interface and prepared from a 3:1 molar mixture of phosphatidylethanolamine and phosphatidylglycerol used to approximate the cell membranes of Gram positive bacteria. The Langmuir film balance measurements show that both peptides perturb the lipid monolayers causing an increase in surface pressure, and the BAM studies show that each results in the formation of small domains within the lipid films, around 5 μm diameter. The overall change in monolayer surface pressure caused by PG-1, however, is a little more pronounced than that due to RTD-1 (+8.5 mN·m(-1) vs +5.5 mN·m(-1)), and the rate of its initial interaction with the monolayer is a little more rapid than that for RTD-1. The neutron reflectivity studies also show differences for PG-1 and RTD-1, with the model fits to these data showing that the more amphiphilic PG-1 becomes fully embedded within the lipid film-causing an extension of the lipid acyl chains but leaving the thickness of the lipid headgroup layer unaffected-while RTD-1 is seen to insert less deeply-causing the same extension of the lipid acyl chains as PG-1 but also causing a significant increase in thickness of the lipid headgroup layer. The various differing effects of the two peptides on anionic lipid monolayers are discussed in the context of their differing hemolytic activities, and their proposed differing propensities to form transmembrane pores.

Influence of atmospheric waves on the formation and the maintenance of the subtropical jet during the Northern Hemisphere winter—A new method for analyzing the responses to specific forcings

AbstractThis paper introduces a new analysis method that can isolate the responses to specific forcings within meteorological data. By using the zonal mean primitive equations on the sphere, it is possible to break down the meridional circulation, the acceleration of zonal wind, temperature change, and surface pressure change into their individual contributions, which are directly associated with various forcings. This analysis technique can be applied to a wide range of problems relating to climate and its variability. To demonstrate the application of the technique, the formation and maintenance of the subtropical jet during the Northern Hemisphere winter are examined. It is found that atmospheric waves play a crucial role in both the climatological maintenance and the day‐to‐day (and month‐to‐month) variabilities of the jet. While stationary waves are the dominant catalyst for maintaining the jet in its climatological state, synoptic waves play an important role in generating the month‐to‐month variability of the jet.

Chondroitin sulfate interacts mainly with headgroups in phospholipid monolayers

Sulfated glycosaminoglycans are precursors of the extracellular matrix used to treat diseases related to blood clotting and degenerative joint diseases. These medical applications have been well established, but the mode of action at the molecular level, which depends on the interaction with cell membranes, is not known in detail. In this study, we investigated the interaction between chondroitin sulfate (CS) and phospholipid monolayers that mimic cell membranes. From surface pressure isotherms and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), CS was found to interact mainly with the polar groups of dipalmitoyl phosphatidylcholine (DPPC) and dipalmitoyl phosphatidylglycerol (DPPG), with negligible penetration into the hydrophobic tails and only small changes in monolayer elasticity for the packing corresponding to a real cell membrane. The changes in surface pressure and surface potential isotherms depended on CS concentration and on the time allowed for its adsorption onto the monolayer, which points to a dynamic adsorption-desorption process. The charge of the phospholipid was also relevant, since CS induced order into DPPC monolayers while the opposite occurred for DPPG, according to the PM-IRRAS spectra. In summary, interaction with polar groups is responsible for the CS effects on model cell membranes.

Impacts of parameterized orographic drag on the Northern Hemisphere winter circulation.

A recent intercomparison exercise proposed by the Working Group for Numerical Experimentation (WGNE) revealed that the parameterized, or unresolved, surface stress in weather forecast models is highly model‐dependent, especially over orography. Models of comparable resolution differ over land by as much as 20% in zonal mean total subgrid surface stress (τtot). The way τtot is partitioned between the different parameterizations is also model‐dependent. In this study, we simulated in a particular model an increase in τtot comparable with the spread found in the WGNE intercomparison. This increase was simulated in two ways, namely by increasing independently the contributions to τtot of the turbulent orographic form drag scheme (TOFD) and of the orographic low‐level blocking scheme (BLOCK). Increasing the parameterized orographic drag leads to significant changes in surface pressure, zonal wind and temperature in the Northern Hemisphere during winter both in 10 day weather forecasts and in seasonal integrations. However, the magnitude of these changes in circulation strongly depends on which scheme is modified. In 10 day forecasts, stronger changes are found when the TOFD stress is increased, while on seasonal time scales the effects are of comparable magnitude, although different in detail. At these time scales, the BLOCK scheme affects the lower stratosphere winds through changes in the resolved planetary waves which are associated with surface impacts, while the TOFD effects are mostly limited to the lower troposphere. The partitioning of τtot between the two schemes appears to play an important role at all time scales.

Characterization of N-cyclohexylmethacrylamide LB thin films for room temperature vapor sensor application

ABSTRACTThis study reports the synthesis, characterization and gas sensing applications of N-cyclohexylmethacrylamide (NCMA) monomer material using FT-IR, 1H and 13C NMR, UV-visible spectroscopy, Quartz Crystal Microbalance (QCM) and Langmuir-Blodgett (LB) thin film deposition techniques. The thin film deposition conditions of NCMA monomer material, which are prepared by LB film technique, are characterized by UV-visible spectroscopy and QCM system. The sensing behaviors of the LB film with respect to volatile organic compounds (VOCs) at room temperature are investigated. Surface pressure change as a function of surface area of NCMA molecule at the water surface shows a well-organized and stable monolayer at 18 mN m−1 surface pressure value for LB film deposition. Transfer ratio values are found to be ≥ 0.94 for quartz glass and ≥ 0.93 for quartz crystal substrate. The typical frequency shift per layer is obtained 20.10 Hz/layer and the deposited mass onto a quartz crystal is calculated as 824.62 ng/layer. The sensing responses of the LB films against chloroform, dichloromethane, acetone, toluene, benzene and ethanol are measured by QCM system. The sensitivities of the NCMA LB film sensor are determined between 0.085 and 0.029 Hz ppm−1. Sensitivities with detection limits are between 35.29 and 100.33 ppm against organic vapors. These results can be concluded that the monomer LB film sample is found to be significantly more sensitive to chloroform and dichloromethane vapors than others organic vapors used in this work. This material may find potential applications in the development of room temperature organic vapor sensing.

Mixed monolayers of a photosensitive crown-ether derivative and a polymer as the prototype of sensing nanomaterials

The interaction of a photosensitive and surface-active dithiacrown-ether derivative (in polymer-based mixed monolayers) with Cd 2+ from aqueous solutions, which has been found by surface pressure, potential and spectral changes, is promising for future applications in nanosized sensing materials.

Changes in the south Asian monsoon low level jet during recent decades and its role in the monsoon water cycle

June–September mean wind at 850hPa from ERA-Interim, MERRA and NCEP2 reanalyses shows an increasing trend in the south Asian monsoon Low Level Jet (LLJ) during 1980–2014. In the sub-seasonal scale, the LLJ during July and September exhibits increasing trend, while August shows a decreasing trend. Lesser changes in surface pressure over heat low region and weaker Bay of Bengal convection lead to weakening of LLJ during August while an intense heat low during September results stronger LLJ. The associated moisture transport changes affect the monsoon hydrological cycle with decreasing precipitation during August and increasing precipitation during September.

Effects of Leucin-Enkephalins on Surface Characteristics and Morphology of Model Membranes Composed of Raft-Forming Lipids

During the last decades opioid peptides, like enkephalins (Tyr-Gly-Gly-Phe-Met/Leu) are subject to extensive studies due to their antinociceptive action in organism. According to the membrane catalysis theory, in order to adopt a proper conformation for binding to their receptors, opioid peptides interact with the lipid phase of the membrane receptor surrounding. With this regard, the aim of the present work was to study the effects of synthetic leucine-enkephalin and leucine-enkephalinamide on surface characteristics and morphology of lipid monolayers, composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, sphingomyelin, and cholesterol alone and with their mixtures. The lipids were chosen to represent a model of a membrane raft, since it is known that G-protein-coupled receptors, including opioid receptors, are located preferably in membrane rafts. By using Langmuir's monolayer method, the change in surface pressure of the model membranes before and after the addition of the synthetic enkephalins was studied, and the compressional moduli of the lipids and lipid-peptides monolayers were determined. In addition, by Brewster angle microscopy, the surface morphology of the lipid monolayers alone and after the injection of both enkephalins was monitored. Our results showed that both leucine-enkephalins affected the lipid monolayers surface characteristics, and led to an increase in surface density of the mixed surface lipids/enkephalins films at loose lipid packing. This effect was more pronounced for the enkephalinamide, suggesting a different mechanism of interaction for the amidated enkephalin with the lipid phase, as compared to leucine-enkephalin.