Publications

Click on image next to published articles for PDF

12. Milk as a Constituent Resource for HDL. N. Argov, M. Barboza, J. Froehlich, D.A. Bricarello, A.W. Szmodis, A. Zivkovic, D. Lemay, S. Freeman, J. Smilovitz, C. Lebrilla, A.N. Parikh, and B. German. (Manuscript in Preparation.)

11. PEG8S Eﬀects on DPPC Domain Formation and Stability. R. El-khouri, A.W. Szmodis, S.L. Frey, K.C. Lee, and A.N. Parikh. (Manuscript in Preparation)

10. Early stages of oxidative stress-induced membrane permeabilization: a neutron reﬂectometry study. H. Smith, A.W. Szmodis, M.C. Howland, A.N. Parikh, and J. Majewski (Manuscript Submitted, JACS)

9. Thermally Induced Phase Separation In Supported Bilayers of Glycosphingolipid and Phospholipid Mixtures. A.W. Szmodis, C.D. Blanchette, M.L. Longo, C.A. Orme, and A.N. Parikh (Manuscript in Preparation)

8. Nucleation and Growth of Interdigitated Domains in Supported f-DPPC Lipid Bilayers. B. Sanii, A.W. Szmodis, and A.N. Parikh (Manuscript in Preparation)

7. Direct Visualization of Thermally-Induced Phase Separation in Supported Phospholipid Bilayers Using Imaging Ellipsometry. A.W. Szmodis, C.D. Blanchette, A. Levchenko, A. Navrotsky, M.L. Longo, C.A. Orme, and A.N. Parikh. Soft Matter Communication, 4 (6), 1161 (2008).

Via imaging ellipsometry, we study phase transition dynamics induced by selective gelation of one component in a binary supported phopholipid bilayer. We find the modulation of two co-attendant morphological features: emergence of extended defect chains due to net change in molecular areas and fractal-like domains suggesting weak line tension. A time-lapse analysis of the ellipsometric images reveals the cluster size of 4-20 molecules undergoing gelation indicating weak cooperativity. These results demonstrate the use of ellipsometry for in-situ, label-free, non-contact, and large-area imaging of dynamics in interfacial films.

6. Featured Cover Article: Characterization of Physical Properties of Supported Phospholipid Membranes Using Imaging Ellipsometry at Optical Wavelengths. Michael C. Howland, Alan W. Szmodis, Babak Sanii, and Atul N. Parikh. Biophysical Journal, 92 (4), 1306 (2007) (First two authors contributed equally to this work).

Sub-nanometer scale vertical z-resolution coupled with large lateral area imaging, label-free, non-contact, and in-situ advantages make the technique of optical imaging ellipsometry highly suitable for quantitative characterization of lipid bilayers supported on oxide substrates and submerged in aqueous phases. This paper demonstrates the versatility of imaging ellipsometry in quantitative characterization of structural and functional properties of supported phospholipid membranes using previously well-characterized examples. These include (1) a single-step determination of bilayer thickness to 0.2 nm accuracy and large-area lateral uniformity using photochemically patterned single DMPC bilayers; (2) hydration-induced spreading kinetics of a single fluid POPC bilayers to illustrate the in-situ capability and image acquisition speed; (3) a large-area morphological characterization of phase-separating binary mixtures of DPLC and galactosylceramide; and (4) binding of cholera-toxin B sub-units to GM1 incorporating bilayers. Additional insights derived from the present ellipsometric measurements are also discussed for each of these applications. Agreement with previous studies confirms that imaging ellipsometry provides a simple and convenient tool for a routine, quantitative characterization of these membrane properties. Our results also suggest that imaging ellipsometry complements more widely used fluorescence and scanning probe microscopies by combining large-area measurements with high vertical resolution without the use of labeled lipids.

5. Featured Cover Article: Glass Bead Probes of Local Morphological and Mechanical Properties of Supported Membranes. S. S. Dixit, A. W. Szmodis, A. N. Parikh, Chem Phys. Chem, 7, 1678-1681 (2006) (First two authors contributed equally to this work).

Non-specific interactions between glass beads and supported lipid membranes can be used as a simple tool to characterize their local structural and mechanical properties. The affinity difference of the beads for bilayers and glass results in mesoscale amplification of the underlying membrane patterns and void-defects producing mesoscale optical contrasts. Beads differentiate monolayers from fluid bilayers by inducing a qualitatively different elastic response, characterized by undeformed binding for monolayers and membrane wrapping for bilayers.

4. Influence of Chromium and Molybdenum on the Corrosion of Nickel Based Alloy Systems. J.R. Hayes, J. J. Gray, A. Szmodis, and C. A. Orme, Corrosion, (2006)

Alloy 22 (UNS N06022) is the candidate material for the corrosion resistant, outer barrier of the Yucca Mountain nuclear waste containers. One of the potential corrosion degradation modes of the container is uniform or passive corrosion. Therefore it is of importance to understand the stability of the oxide film, which will control the passive corrosion rate of Alloy 22. Many variables such as temperature, composition and pH of the electrolyte, applied potential, and microstructure and composition of the base metal would determine the thickness and composition of the oxide film. The purpose of this research work was to use electrochemical and surface analysis techniques to explore the influence of solution pH and applied potential on the characteristics of the oxide film formed on Alloy 22 and two experimental alloys containing differing amounts of chromium (Cr) and molybdenum (Mo). Results confirm that bulk metal composition is fundamental to the passive behavior and potential breakdown of the studied alloys. In these preliminary results, welded and non-welded Alloy 22 did not show differences in their anodic behavior.

3. Morphological Changes in Metal/Metal-Oxide Systems.

C.A. Orme, K.L. Anderson, J.R. Hayes, A.W. Szmodis, J.P. Bearinger, NACE Corrosion Research in Progress (2004).

2. Diffraction from 1D and 2D Quasicrystalline Gratings.

N. Ferralis, A.W. Szmodis, R.D. Diehl

American J. Phys. 72 (9), (2004).

The diffraction from one- and two-dimensional aperiodic structures is studied by using Fibonacci and other aperiodic gratings produced by several methods. By examining the laser diffraction patterns obtained from these gratings, the effects of aperiodic order on the diffraction pattern was observed and compared to the diffraction from real quasicrystalline surfaces. The correspondence between diffraction patterns from two-dimensional gratings and from real surfaces is demonstrated.

1. Low-energy Electron Diffraction from Quasicrystal Surfaces. R. D. Diehl, J. Ledieu, N. Ferralis, A. W. Szmodis, and R. McGrath Journal of Physics: Condensed Matter, 15:R63, (2003).

The discovery of ordered but aperiodic quasicrystal structures has required the development of new diffraction methods to determine their structures. The purpose of this review is to highlight the challenge sposed by the aperiodicity of quasicrystals to the study of their surface structures by low-energy electron diffraction (LEED). This paper describes how the LEED technique has been thus far adapted to study several quasiperiodic surface structures, and summarizes the results of those studies. It also presents new spot-profile-analysis LEED results from the five fold surface of Al–Pd–Mn. An x-ray diffraction experiment and a He-atom diffraction experiment, both on Al–Pd–Mn, are also described for comparison.

Publications

Invited Talks

Invited Application Note

Posters & Published Abstracts

1. ”Membrane Dynamics at the solid-liquid interface: Spreading, Interdigitation and Domain Gellation”, Szmodis, A.W., Sanii, B. and Parikh, A.N., Forschungszentrum Karlsuhe Institute for Nanotechnology, Eggenstein-Leopoldshafen, Germany, September 2007.

1. ”Supported phospholipid bilayer membranes - Part 1” Howland, M.C., Szmodis, A.W. and Parikh, A.N., Nanopticum 2006, 6-7.

14. Szmodis, A.W., Howland, M.C., Blanchette, C.D., Longo, M.L., Orme, C.A., and Parikh, A.N., Label-free Characterization of Biomembranes and Phase Separation Processes Using Imaging Ellipsometry. Biomembrane Frontiers Meeting March 2008

13. Szmodis, A.W., Blanchette, C.D., Levchenko, A., Navrotsky, A., Longo, M.L., Orme, C.A., and Parikh, A.N., Direct Visualization on Thermally-Induced Phase Separation in Supported Bilayers Using Imaging Ellipsometry. Biophysical Society Meeting Feb. 2008.

12. Smith, H., Ma jewski, J., Szmodis, A.W., Howland, M.C. and Parikh, A.N. Understanding the process of membrane photolithography. Biophysical Society Meeting Feb. 2008.

11. Szmodis, A.W., Blanchette, C.D., Levchenko, A., Navrotsky, A., Longo, M.L., Orme, C.A., and Parikh, A.N., Direct Visualization on Thermally-Induced Phase Separation in Supported Bilayers Using Imaging Ellipsometry. Novel Model Systems for Bimolecular Lipid Membranes, Schloss Ringberg, Germany, Sept. 2007.

10. Szmodis, A.W., Blanchette, C.D., Levchenko, A., Navrotsky, A., Longo, M.L., Orme, C.A., and Parikh, A.N., Direct Visualization on Thermally-Induced Phase Separation in Supported Bilayers Using Imaging Ellipsometry. Biophysical Society Meeting Mar. 2007.

9. Szmodis, A.W., Sanii, B., Howland, M.C. and Parikh A.N., Direct Visualization on Thermally-Induced Phase Separation in Supported Bilayers Using Imaging Ellipsometry. American Chemical Society Meeting Sept. 2006.

8. Szmodis, A.W., Dixit, S. and Parikh A.N., Glass Bead Probes of Morphology and Mechanical Properties in Fluid, Supported Membranes. Biophysical Society Meeting Feb. 2006.

7. Szmodis, A.W., Dixit, S. and Parikh A.N., Colloidal Interactions with Lipid Bilayers. Material Research Society Meeting Mar. 2005.

6. Szmodis, A.W., Dixit, S. and Parikh A.N., Bowlingballs on bilayers: Ampliﬁcation of patterns in lipid bilayers through colloidal adhesion. Biophysical Journal 88 (1): 413A Part 2 Suppl. S, Jan. 2005.

5. Brozell, A.M., Muha, M., Szmodis A.W., et al., Design and characterization of supported phospholipid membranes on colloidal layers. Biophysical Journal 88 (1): 413A-414A Part 2 Suppl. S, Jan. 2005.

4. Yee C.K., Butti A.R.S., Szmodis A.W., et al., Non-ideal mixing and dynamics of phase separation in ﬂuid lipid billayers. Abstracts of Papers of the American Chemical Society 230: U1240-U1240 417-COLL, Aug. 2005.

3. Dixit, S., Szmodis, A.W. and Parikh A.N., Functional Membrane Consequences of Membrane Fluidity: Bead Adheasion. California Institute for Quantitative Biosciences Meeting May 2005.

2. Environmental Influence on Passive Films Formed on Alloy 22 (UNSNO6022). Szmodis, A.W., Anderson, K.L., Farmer, J.C., Lian, T., Orme, Proceedings National Association of Corrosion Engineers - San Diego, CA March (2003).

The passive corrosion rate of Alloy 22 is exceptionally low in a wide range of aqueous solutions, temperatures and electrochemical potentials, Alloy 22 contains approximately

22% chromium (Cr) by weight; thus, it forms a Cr-rich passive film in most environments. Very little is known about the composition, thickness and other properties

of this passive film. The aim of this research was to determine the general characteristics of the oxide film that forms on Alloy 22, as a function of solution pH, temperature and

applied electrochemical potential.

1. Characteristics of the oxides films formed on Alloy C-22. Szmodis, A.W., Anderson, K.L., Farmer, J.C., Lian, T., Orme, C.A. 26th Symposium on the Scientific Basis for Nuclear Waste Management as held at the 2002 MRS Fall Meeting; Boston, MA; USA; 2-5 Dec. 2002. pp. 757-764. (2003)

The passive corrosion rate of Alloy C-22 is exceptionally low in a wide range of aqueous solutions, temperatures and electrochemical potentials. Alloy C-22 contains approximately 22% chromium (Cr) by weight; thus, it forms a Cr-rich passive film in most environments. A study of the composition, thickness and other properties of the passive film was undertaken to better understand the role of the protective oxide in preventing corrosion. In general the oxide film is expected to be a function of solution pH, temperature and applied electrochemical potential. In this work we focus on the oxide films that form at pH = 8.