Boris M. Aizenbud’s research while affiliated with Massachusetts Institute of Technology and other places

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Publications (11)


Diffusion of molecules on biological membranes of nonplanar form. II. Diffusion anisotropy
  • Article

November 1985

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19 Reads

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20 Citations

Biophysical Journal

B M Aizenbud

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N D Gershon

Molecules diffusing on nonplanar membranes, which have different amounts of corrugation in different directions, may experience dissimilar diffusion coefficients in each direction. Smith et al. (1979, Proc. Natl. Acad. Sci. USA, 76:5641-5644) measured diffusion anisotropy on fibroblast cell membranes in which the ratio of the diffusion coefficients, in different directions, was 0.27. In the present work we calculate the effect of anisotropic corrugation on the rate of diffusion of molecules on membranes. We find that part of the anisotropy reported by Smith et al. (1979, Proc. Natl. Acad. Sci. USA, 76:5641-5644) can be explained by the membrane nonplanarity, and we present the way of calculating this geometric factor.


Diffusion of molecules on biological membranes of nonplanar form. A theoretical study

July 1982

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19 Reads

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75 Citations

Biophysical Journal

Lateral mobility of molecules on cell membranes has been recently studied by fluorescence photobleaching recovery (FPR) techniques. The interpretation of these results in terms of diffusion along the membranes is based on the assumption that the surface is planar, although biological membranes may have blebs and microvilli. To study the effect of nonplanarity on the diffusion rate, the diffusion equation along curved surfaces was derived and was solved numerically for a "wavy" surface of the form A cos kx cos ky. Calculations show that for k = 10 pi micrometer-1 and a bleached spot of 1 micrometer in diameter, the time dependence of the intensity of fluorescence in the bleached spot depends on A at A less than 0.5 micrometer, while at higher values of A (a and 2 micrometer) the dependence is weak. If one calculates diffusion coefficients from FPR measurements and assumes that the membrane is planar, the resulting diffusion coefficient is not less than about half of the real one. Because of the tortuous shape of the spot boundary, increasing the microvilli length from 0.5 micrometer to 1 or 2 micrometer does not change the diffusion rates. These considerations are valid for times when the diffusion is dominated by molecules that were initially located close to the spot boundary.


Optimization of model internal combustion engine

April 1982

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63 Reads

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73 Citations

We optimize the operating conditions of a model internal combustion engine to obtain maximal efficiency. The model engine consists of a cylinder equipped with a piston containing a working fluid, coupled to a heat bath and heated by internal combustion with a rate of heating that is very weakly dependent on the temperature and pressure of the working fluid. We consider operation of the piston under the influence of an external pressure. The model engine includes valves allowing the exhaust and intake of the working fluid. It is found that the optimal operation has an optimal compression ratio and an optimal energy to be exhausted with the working fluid. The results are demonstrated with a numerical example. Also presented are optimizations for this system of the average power, and optimization of the work for a given specified average power.




Power considerations in the operation of a piston fitted inside a cylinder containing a dynamically heated working fluid

July 1981

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15 Reads

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34 Citations

We determine the optimal motion of a piston fitted in a cylinder containing a gas, pumped with a given time‐dependent rate of heating and coupled to a heat bath, in order to maximize the power obtained. The dependence of the optimal power, and the corresponding optimal operating time, on the form of the heating function is studied. Furthermore, we determine the maximum work production obtainable from the system for a given specific power output.


Light scattering from fluids. A semi-phenomenological calculation of the coupling constants between the orientational and translational motion

June 1981

Physica A Statistical Mechanics and its Applications

The coupling parameters X and Z between translational and orientational motions, which determine the lineshapes of the VH and HH depolarized light scattering spectra respectively, are calculated. By using a simple model that explains the connection between rotational and translational motions, it is shown that X and Z are proportional to k2ηr/ρ. The correct order of magnitude of the proportionality coefficient is obtained.


Hydrodynamic equations and VH light scattering from viscoelastic (solid-like and fluid-like) systems. Phenomenological approach

May 1981

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1 Citation

Physica A Statistical Mechanics and its Applications

The dynamics of solid-like and fluid-like systems is studied whereby the expressions for the VH light scattering spectra for these systems are obtained. It is shown that for small values of k, the VH spectrum of fluid-like systems does not contain the shifted parts in contradistinction to the spectrum of the solid-like systems.



Hydrodynamic equations and VH light scattering from binary mixtures of fluids of nonspherical molecules

December 1977

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3 Reads

Physica A Statistical Mechanics and its Applications

The hydrodynamics of mixtures of liquids of nonspherical molecules is considered by using the method of ``generalized hydrodynamic matrix'' (Felderhof-Selwyn-Oppenheim theory). The resulting hydrodynamic equations are applied to calculate the low frequency depolarized light scattering spectra based on Gershon-Oppenheim theory. Two possible cases in the VH geometry are considered.


Citations (5)


... Off-resonant [10,11], resonant and near-resonant (discrete) Raman scattering [10][11][12][13][14][15][16][17][18][19][20][21][22], as well as Raman scattering via dissociative continuum from diatomic molecules [7,9,[23][24][25][26], are objects of numerous experimental and theoretical studies. The system of molecular iodine has been chosen for many studies [7-11, 16, 21, 22], since this transition belongs to the visible region, and the spectroscopic characteristics of both states are well known (see [27][28][29], e.g.). ...

Reference:

Near-resonant rovibronic Raman scattering from 0 g + (bb) valence state via the D0 u + ion-pair state in iodine molecule
Resonance Raman scattering amplitude calculations for diatomic molecules
  • Citing Article
  • January 1981

Chemical Physics Letters

... Engine manufacturers are constantly striving to improve such models to enable the analysis and optimization of critical performance indicators. Research on mathematical modeling of internal combustion engines dates back to the 1970s [1][2][3][4][5] with multifaceted applications in control system design, performance prediction, and emission optimization. Model reduction is crucial for real-time applications like control system optimization and system monitoring, as it enhances computational efficiency. ...

Optimization of model internal combustion engine
  • Citing Article
  • April 1982

... Refs. [13][14][15][16] used the optimization results obtained in Refs. [11,12] to study the optimal MPs of the piston under the maximum power output [13] and the maximum work output [14] when the power input was given, as well as the optimal operation processes of internal [15] and external [16] combustion engines. ...

Power considerations in the operation of a piston fitted inside a cylinder containing a dynamically heated working fluid
  • Citing Article
  • July 1981

... Because in a surface bleach configuration the cylindrical OHC membrane is bending away from the focal plane circumferentially, the lateral mobility monitored by FRAP will appear to be anisotropic even if the underlying diffusion in the surface of the membrane is isotropic (52). At a point where the membrane makes an angle u with the focal plane, the diffusion coefficient is reduced in the circumferential direction by a factor of (cos u) 2 . ...

Diffusion of molecules on biological membranes of nonplanar form. II. Diffusion anisotropy
  • Citing Article
  • November 1985

Biophysical Journal

... Lateral diffusion on curved geometries has been investigated theoretically both on static surfaces [8,9] and dynamically fluctuating membranes [9][10][11][12][13]. The diffusion coefficient due to the geometrical effect of a curved surface and that arising from the interaction between the Brownian particle and membrane has been obtained. ...

Diffusion of molecules on biological membranes of nonplanar form. A theoretical study
  • Citing Article
  • July 1982

Biophysical Journal