Phase behavior of two-component lipid membranes: theory and experiments

The structure of the ripple phase of phospholipid membranes remains poorly understood in spite of a large number of theoretical studies, with many experimentally established structural features of this phase unaccounted for. In this article we present a phenomenological theory of phase transitions in single- and two-component achiral lipid membranes in terms of two coupled order parameters -- a scalar order parameter describing {\it lipid chain melting}, and a vector order parameter describing the {\it tilt of the hydrocarbon chains} below the chain-melting transition. This model reproduces all the salient structural features of the ripple phase, providing a unified description of the phase diagram and microstructure. In addition, it predicts a variant of this phase which does not seem to have been experimentally observed. Using this model we have calculated generic phase diagrams of two-component membranes. We have also determined the phase diagram of a two-component lipid membrane from x-ray diffraction studies on aligned multilayers. This phase diagram is found to be in good agreement with that calculated from the model.Comment: 10 pages, 10 figure

Theory of the asymmetric ripple phase in achiral lipid membranes

We present a phenomenological theory of phase transitions in achiral lipid membranes in terms of two coupled order parameters -- a scalar order parameter describing lipid chain melting, and a vector order parameter describing the tilt of the hydrocarbon chains below the chain-melting transition. Existing theoretical models fail to account for all the observed features of the phase diagram, in particular the detailed microstructure of the asymmetric ripple phase lying between the fluid and the tilted gel phase. In contrast, our two-component theory reproduces all the salient structural features of the ripple phase, providing a unified description of the phase diagram and microstructure

Brillouin Scattering Studies of La_{0.77}Ca_{0.23}MnO_3 Across Metal-Insulator Transition

Temperature-dependent Brillouin scattering studies have been carried out on La_{0.77}Ca_{0.23}MnO_3 across the paramagnetic insulator - ferromagnetic metal (I-M) transition. The spectra show a surface Rayleigh wave (SRW) and a high velocity pseudo surface acoustic wave (HVPSAW) besides bulk acoustic waves (BAW). The Brillouin shifts associated with SRW and HVPSAW show blue-shifts, where as the frequencies of the BAW decrease below the I-M transition temperature (T_C) of 230 K. These results can be understood based on the temperature dependence of the elastic constants. We also observe a central peak whose width is maximum at T_C.Comment: 7 pages, 8 figure

Stability Control Structure of Hovercraft Prototype Utilising PID Controller

Hovercraft is a method of transportation as an option for clients who remain on the waterway and swamp surface. The issue with hovercraft is when dubious climate and natural condition, e.g. wind speed and wave tallness exasperate solidness of hovercraft to jeopardise the driver. We propose an approach to keep up adjust of the hovercraft by controlling the focal point of gravity (PG) to be determined position. The controller monitors the position of load to change the position. A 6-DOF IMU Sensor MPU 6050 was utilised to create information as an examination with setpoint. PID control strategy was employed. The test outcome demonstrates that the model of air cushion vehicle could keep its adjust the axis orientation of the roll in spite of the fact that it was less compelling in the pitch pivot direction

Obesity and Cardiovascular Health Differences Between Urban and Suburban Philadelphia High School Athletes

Introduction: The strongest risk factor for primary hypertension in children is obesity, and concern for pediatric hypertension rises with the rising prevalence of obesity in American children. Specifically, in urban Philadelphia schools from 2009 to 2012, preparticipation physical evaluations (PPEs) demonstrated a positive correlation between blood pressure measurements demonstrating stage 1 or 2 hypertension and elevated body mass index (P \u3c 0.00001). Objective: The purpose was to identify potential differences in cardiovascular health and prevalence of obesity between adolescents in the urban and suburban Philadelphia areas. Methods: Data from PPEs administered to urban Philadelphia high school athletes in 2018 by the Athlete Health Organization (AHO) was analyzed and compared to data from the Simon’s Heart Foundation’s HeartBytes registry, which provided data regarding suburban Philadelphia students. Demographic information and basic physical examination data were collected. Each participant’s body mass index (BMI) was categorized by percentile for age, and blood pressures were classified according to American Heart Association pediatric guidelines. Results: Analysis of the AHO data shows that 44.9% of urban students who completed PPEs in 2018 were overweight or obese, and that 43.1% of these students had blood pressures that would qualify as either stage 1 or 2 hypertension. Further comparison to the HeartBytes data is forthcoming. Conclusion: Given results to date, it is expected that upon conclusion of the study, the data will support the hypothesis that rates of hypertension and obesity will be higher in the urban underserved population than in the suburban population

SURFACE RESPONSE METHODOLOGY FOR DEVELOPMENT AND OPTIMIZATION OF NAPROXEN SUSTAINED RELEASE TABLETS

Objective: The current work focuses on the development and optimization of Naproxen 800mg sustained release tablets using surface response methodology.Methods: The drug release was controlled by formulating it into a sustained release tablet. The formulae was developed using various individual concentrations and viscosity grades of HPMC polymers for Naproxen SR tablets. The compatibility of polymers along with pure drug Naproxen was evaluated using FTIR and DSC studies. The tablets were prepared and Pre- and Post-compressional parameters, In-vitro dissolution testing, release rate kinetics and stability studies were evaluated.Results: The FT-IR and DSC spectras confirms the absence of chemical interaction between drug and polymers. All the Pre-compressional and Post-compressional parameters were found to be in limits. From the dissolution testing of all these formulations the low and high level of polymer concentrations which were within the range of Target product profile was determined. The design space as defined by the above experiments is within 21.3 to 22.8 range of the total polymer concentration. The data for stability studies revealed that no considerable differences in drug content and dissolution rates for a period of 6 months as per ICH guidelines.Conclusion: Based on the above results, a design space for all the three polymers was successfully developed within which when the tablets are fabricated, the target product profile will always be achieved. Key-words: Rheumatoid arthritis; Naproxen; Sustained release matrix system; Hydrophilic polymers