Peter Pinsky

All Publications

• Celebrating the 95th birthday of Professor Karl S. Pister CMES-COMPUTER MODELING IN ENGINEERING & SCIENCES Austin, M., Hughes, T. R., Eibeck, P., Pines, D., Agogino, A., Oden, J., Martin-Atilano, L., Greene, B., Sture, S., Lutolf-Carroll, C., Ramm, E., Hawthorn, P., Simons, B., Torres, A., Felippa, C., Smith, B., Pinsky, P., May, G., Humphreys, S. 2021

  View details for DOI 10.32604/cmes.2021.018838

  View details for Web of Science ID 000720873300001

• Fluid and Osmotic Pressure Balance and Volume Stabilization in Cells Dedicated to Professor Karl Stark Pister for his 95th birthday CMES-COMPUTER MODELING IN ENGINEERING & SCIENCES Pinsky, P. M. 2021

  View details for DOI 10.32604/cmes.2021.017740

  View details for Web of Science ID 000696938000001

• A Mathematical Model of Corneal Metabolism in the Presence of an Iris-Fixated Phakic Intraocular Lens. Investigative ophthalmology & visual science Davvalo Khongar, P., Pralits, J. O., Cheng, X., Pinsky, P., Soleri, P., Repetto, R. 2019; 60 (6): 2311–20

  Abstract

  Purpose: Corneal endothelial cell loss is one of the possible complications associated with phakic iris-fixated intraocular lens (PIOL) implantation. We postulate that this might be connected to the alteration of corneal metabolism secondary to the lens implantation.Methods: A mathematical model of transport and consumption/production of metabolic species in the cornea is proposed, coupled with a model of aqueous flow and transport of metabolic species in the anterior chamber.Results: Results are presented both for open and closed eyelids. We showed that, in the presence of a PIOL, glucose availability at the corneal endothelium decreases significantly during sleeping.Conclusions: Implantation of a PIOL significantly affects nutrient transport processes to the corneal endothelium especially during sleep. It must still be verified whether this finding has a clinical relevance.

  View details for DOI 10.1167/iovs.19-26624

  View details for PubMedID 31117123

• Biofluid modeling of the coupled eye-brain system and insights into simulated microgravity conditions. PloS one Salerni, F., Repetto, R., Harris, A., Pinsky, P., Prud'homme, C., Szopos, M., Guidoboni, G. 2019; 14 (8): e0216012

  Abstract

  This work aims at investigating the interactions between the flow of fluids in the eyes and the brain and their potential implications in structural and functional changes in the eyes of astronauts, a condition also known as spaceflight associated neuro-ocular syndrome (SANS). To this end, we propose a reduced (0-dimensional) mathematical model of fluid flow in the eyes and brain, which is embedded into a simplified whole-body circulation model. In particular, the model accounts for: (i) the flows of blood and aqueous humor in the eyes; (ii) the flows of blood, cerebrospinal fluid and interstitial fluid in the brain; and (iii) their interactions. The model is used to simulate variations in intraocular pressure, intracranial pressure and blood flow due to microgravity conditions, which are thought to be critical factors in SANS. Specifically, the model predicts that both intracranial and intraocular pressures increase in microgravity, even though their respective trends may be different. In such conditions, ocular blood flow is predicted to decrease in the choroid and ciliary body circulations, whereas retinal circulation is found to be less susceptible to microgravity-induced alterations, owing to a purely mechanical component in perfusion control associated with the venous segments. These findings indicate that the particular anatomical architecture of venous drainage in the retina may be one of the reasons why most of the SANS alterations are not observed in the retina but, rather, in other vascular beds, particularly the choroid. Thus, clinical assessment of ocular venous function may be considered as a determinant SANS factor, for which astronauts could be screened on earth and in-flight.

  View details for DOI 10.1371/journal.pone.0216012

  View details for PubMedID 31412033

• A Constitutive Model for Swelling Pressure and Volumetric Behavior of Highly-Hydrated Connective Tissue JOURNAL OF ELASTICITY Pinsky, P. M., Cheng, X. 2017; 129 (1-2): 145–70

  View details for DOI 10.1007/s10659-016-9616-z

  View details for Web of Science ID 000410258500008

• A simple mathematical model for the collagen architecture of normal and keratoconic human corneas Pinsky, P. M., Ma, Y., Hwang, Y., Hayes, S., Meek, K. M. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2017

  View details for Web of Science ID 000432176303066

• Ocular and cerebral hemo-fluid dynamics in microgravity: a mathematical model Guidoboni, G., Salerni, F., Harris, A., Prud'homme, C., Szopos, M., Pinsky, P. M., Repetto, R. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2017

  View details for Web of Science ID 000432176300036

• A numerical model for metabolism, metabolite transport and edema in the human cornea COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Cheng, X., Pinsky, P. M. 2017; 314: 323-344

  View details for DOI 10.1016/j.cma.2016.09.014

  View details for Web of Science ID 000392782900017

• Numerical investigation of glucose transport and corneal metabolism in the anterior chamber in the presence of an iris-fixated intraocular lens Khongar, P., Cheng, X., Pralits, J., Repetto, R., Soleri, P., Pinsky, P. M. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2016

  View details for Web of Science ID 000394210604107

• The Balance of Fluid and Osmotic Pressures across Active Biological Membranes with Application to the Corneal Endothelium PLOS ONE Cheng, X., Pinsky, P. M. 2015; 10 (12)

  Abstract

  The movement of fluid and solutes across biological membranes facilitates the transport of nutrients for living organisms and maintains the fluid and osmotic pressures in biological systems. Understanding the pressure balances across membranes is crucial for studying fluid and electrolyte homeostasis in living systems, and is an area of active research. In this study, a set of enhanced Kedem-Katchalsky (KK) equations is proposed to describe fluxes of water and solutes across biological membranes, and is applied to analyze the relationship between fluid and osmotic pressures, accounting for active transport mechanisms that propel substances against their concentration gradients and for fixed charges that alter ionic distributions in separated environments. The equilibrium analysis demonstrates that the proposed theory recovers the Donnan osmotic pressure and can predict the correct fluid pressure difference across membranes, a result which cannot be achieved by existing KK theories due to the neglect of fixed charges. The steady-state analysis on active membranes suggests a new pressure mechanism which balances the fluid pressure together with the osmotic pressure. The source of this pressure arises from active ionic fluxes and from interactions between solvent and solutes in membrane transport. We apply the proposed theory to study the transendothelial fluid pressure in the in vivo cornea, which is a crucial factor maintaining the hydration and transparency of the tissue. The results show the importance of the proposed pressure mechanism in mediating stromal fluid pressure and provide a new interpretation of the pressure modulation mechanism in the in vivo cornea.

  View details for DOI 10.1371/journal.pone.0145422

  View details for Web of Science ID 000367510900008

  View details for PubMedCentralID PMC4697791

• The Balance of Fluid and Osmotic Pressures across Active Biological Membranes with Application to the Corneal Endothelium. PloS one Cheng, X., Pinsky, P. M. 2015; 10 (12): e0145422

  Abstract

  The movement of fluid and solutes across biological membranes facilitates the transport of nutrients for living organisms and maintains the fluid and osmotic pressures in biological systems. Understanding the pressure balances across membranes is crucial for studying fluid and electrolyte homeostasis in living systems, and is an area of active research. In this study, a set of enhanced Kedem-Katchalsky (KK) equations is proposed to describe fluxes of water and solutes across biological membranes, and is applied to analyze the relationship between fluid and osmotic pressures, accounting for active transport mechanisms that propel substances against their concentration gradients and for fixed charges that alter ionic distributions in separated environments. The equilibrium analysis demonstrates that the proposed theory recovers the Donnan osmotic pressure and can predict the correct fluid pressure difference across membranes, a result which cannot be achieved by existing KK theories due to the neglect of fixed charges. The steady-state analysis on active membranes suggests a new pressure mechanism which balances the fluid pressure together with the osmotic pressure. The source of this pressure arises from active ionic fluxes and from interactions between solvent and solutes in membrane transport. We apply the proposed theory to study the transendothelial fluid pressure in the in vivo cornea, which is a crucial factor maintaining the hydration and transparency of the tissue. The results show the importance of the proposed pressure mechanism in mediating stromal fluid pressure and provide a new interpretation of the pressure modulation mechanism in the in vivo cornea.

  View details for DOI 10.1371/journal.pone.0145422

  View details for PubMedID 26719894

  View details for PubMedCentralID PMC4697791

• A structural model for the in vivo human cornea including collagen-swelling interaction. Journal of the Royal Society, Interface / the Royal Society Cheng, X., Petsche, S. J., Pinsky, P. M. 2015; 12 (109)

  Abstract

  A structural model of the in vivo cornea, which accounts for tissue swelling behaviour, for the three-dimensional organization of stromal fibres and for collagen-swelling interaction, is proposed. Modelled as a binary electrolyte gel in thermodynamic equilibrium, the stromal electrostatic free energy is based on the mean-field approximation. To account for active endothelial ionic transport in the in vivo cornea, which modulates osmotic pressure and hydration, stromal mobile ions are shown to satisfy a modified Boltzmann distribution. The elasticity of the stromal collagen network is modelled based on three-dimensional collagen orientation probability distributions for every point in the stroma obtained by synthesizing X-ray diffraction data for azimuthal angle distributions and second harmonic-generated image processing for inclination angle distributions. The model is implemented in a finite-element framework and employed to predict free and confined swelling of stroma in an ionic bath. For the in vivo cornea, the model is used to predict corneal swelling due to increasing intraocular pressure (IOP) and is adapted to model swelling in Fuchs' corneal dystrophy. The biomechanical response of the in vivo cornea to a typical LASIK surgery for myopia is analysed, including tissue fluid pressure and swelling responses. The model provides a new interpretation of the corneal active hydration control (pump-leak) mechanism based on osmotic pressure modulation. The results also illustrate the structural necessity of fibre inclination in stabilizing the corneal refractive surface with respect to changes in tissue hydration and IOP.

  View details for DOI 10.1098/rsif.2015.0241

  View details for PubMedID 26156299

• A computational model for collagen-swelling interaction in the in vivo human cornea Cheng, X., Petsche, S. J., Pinsky, P. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2015

  View details for Web of Science ID 000362882203018

• Three-Dimensional Modeling of Metabolic Species Transport in the Cornea With a Hydrogel Intrastromal Inlay INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE Pinsky, P. M. 2014; 55 (5): 3093-3106

  Abstract

  Intrastromal inlays for refractive correction of presbyopia are being adopted into clinical practice. An important concern is the effect of the inlay on the long-term health of the cornea due to disturbances in the concentration profiles of metabolic species. A three-dimensional metabolic model for the cornea is employed to investigate oxygen, glucose, and lactate ion transport in the cornea and to estimate changes in species concentrations induced by the introduction of a hydrogel inlay.A reaction-diffusion metabolic model, appropriate for highly oxygen-permeable hydrogel inlays, is used to describe cellular consumption of oxygen and glucose and production of lactic acid. A three-layer corneal geometry (epithelium, stroma, endothelium) is employed with a hydrogel inlay placed under a lamellar flap. The model is solved numerically by the finite element method.For a commercially available hydrogel material with a relative inlay diffusivity of 43.5%, maximum glucose depletion and lactate ion accumulation occur anterior to the inlay and both are less than 3%. Below 20% relative diffusivity, glucose depletion and lactate ion accumulation increase exponentially. Glucose depletion increases slightly with increasing depth of inlay placement.The flux of metabolic species is modified by an inlay, depending on the inlay relative diffusivity. For commercially available hydrogel materials and a typical inlay design, predicted changes in species concentrations are small when compared to the variation of concentrations across the normal cornea. In general, glucose depletion and lactate ion accumulation are highly sensitive to inlay diffusivity and somewhat insensitive to inlay depth.

  View details for DOI 10.1167/iovs.13-13844

  View details for Web of Science ID 000339484800037

  View details for PubMedID 24833750

• THREE-DIMENSIONAL MODELING OF METABOLIC SPECIES TRANSPORT IN THE CORNEA WITH A HYDROGEL INTRASTROMAL INLAY. Investigative ophthalmology & visual science Pinsky, P. M. 2014

  Abstract

  Purpose: Intrastromal inlays for refractive correction of presbyopia are being adopted into clinical practice. An important concern is the effect of the inlay on the long-term health of the cornea due to disturbances in the concentration profiles of metabolic species. A 3-D metabolic model for the cornea is employed to investigate oxygen, glucose and lactate ion transport in the cornea and to estimate changes in species concentrations induced by the introduction of a hydrogel inlay. Methods: A reaction-diffusion metabolic model, appropriate for highly oxygen-permeable hydrogel inlays, is used to describe cellular consumption of oxygen and glucose and production of lactic acid. A three-layer corneal geometry (epithelium, stroma, endothelium) is employed with a hydrogel inlay placed under a lamellar flap. The model is solved numerically by the finite element method. Results: For a commercially available hydrogel material with a relative inlay diffusivity of 43.5%, maximum glucose depletion and lactate ion accumulation occur anterior to the inlay and both are less than 3%. Below 20% relative diffusivity, glucose depletion and lactate ion accumulation increase exponentially. Glucose depletion increases slightly with increasing depth of inlay placement. Conclusions: The flux of metabolic species is modified by an inlay, depending on the inlay relative diffusivity. For commercially available hydrogel materials and a typical inlay design, predicted changes in species concentrations are small when compared to the variation of concentrations across the normal cornea. In general, glucose depletion and lactate ion accumulation are highly sensitive to inlay diffusivity and somewhat insensitive to inlay depth.

  View details for DOI 10.1167/iovs.14-13844

  View details for PubMedID 24713482

• The role of 3-D collagen organization in stromal elasticity: a model based on X-ray diffraction data and second harmonic-generated images. Biomechanics and modeling in mechanobiology Petsche, S. J., Pinsky, P. M. 2013; 12 (6): 1101-1113

  Abstract

  Examining the cross-section of the human cornea with second harmonic-generated (SHG) imaging shows that many lamellae do not lie parallel to the cornea's anterior surface but have inclined trajectories that take them through the corneal thickness with a depth-dependent distribution. A continuum mechanics-based model of stromal elasticity is developed based on orientation information extracted and synthesized from both X-ray scattering studies and SHG imaging. The model describes the effects of inclined lamella orientation by introducing a probability function that varies with depth through the stroma, which characterizes the range and distribution of lamellae at inclined angles. When combined with the preferred lamellar orientations found from X-ray scattering experiments, a fully 3-D representation of lamella orientation is achieved. Stromal elasticity is calculated by a weighted average of individual lamella properties based on the spatially varying 3-D orientation distribution. The model is calibrated with in vitro torsional shear experiments and in vivo indentation data and then validated with an in vitro inflation study. A quantitative explanation of the experimentally measured depth dependence of mechanical properties emerges from the model. The significance of the 3-D lamella orientation in the mechanics of the human cornea is demonstrated by investigating and contrasting the effects of previous modeling assumptions made on lamella orientation.

  View details for DOI 10.1007/s10237-012-0466-8

  View details for PubMedID 23288406

• The role of 3-D collagen organization in stromal elasticity: a model based on X-ray diffraction data and second harmonic-generated images BIOMECHANICS AND MODELING IN MECHANOBIOLOGY Petsche, S. J., Pinsky, P. M. 2013; 12 (6): 1101-1113

  Abstract

  Examining the cross-section of the human cornea with second harmonic-generated (SHG) imaging shows that many lamellae do not lie parallel to the cornea's anterior surface but have inclined trajectories that take them through the corneal thickness with a depth-dependent distribution. A continuum mechanics-based model of stromal elasticity is developed based on orientation information extracted and synthesized from both X-ray scattering studies and SHG imaging. The model describes the effects of inclined lamella orientation by introducing a probability function that varies with depth through the stroma, which characterizes the range and distribution of lamellae at inclined angles. When combined with the preferred lamellar orientations found from X-ray scattering experiments, a fully 3-D representation of lamella orientation is achieved. Stromal elasticity is calculated by a weighted average of individual lamella properties based on the spatially varying 3-D orientation distribution. The model is calibrated with in vitro torsional shear experiments and in vivo indentation data and then validated with an in vitro inflation study. A quantitative explanation of the experimentally measured depth dependence of mechanical properties emerges from the model. The significance of the 3-D lamella orientation in the mechanics of the human cornea is demonstrated by investigating and contrasting the effects of previous modeling assumptions made on lamella orientation.

  View details for DOI 10.1007/s10237-012-0466-8

  View details for Web of Science ID 000325815300003

  View details for PubMedID 23288406

• The elusive hair cell gating spring, a potential role for the lipid membrane. journal of the Acoustical Society of America Kim, J., Pinsky, P. M., Steele, C. R., Puria, S., Ricci, A. J. 2013; 133 (5): 3509-?

  Abstract

  Deflection of auditory hair cell hair bundle results in a nonlinear (i.e., non Hookean) force-displacement relationships whose molecular mechanism remains elusive. A gating spring model posits that mechanosensitive channels are in series with a spring such that channel opening puts the activation gate in series with the spring, thus reducing spring extension until further stimulation is provided. Here we present a theoretical analysis of whether the lipid membrane might be the source of nonlinearity. A hair bundle kinematic model is coupled with a lipid membrane model that includes a diffusible compartment into which the tip-link embeds and a minimally diffusive reservoir pool. Using physiological parameters, this model was capable of reproducing nonlinear force-displacement plots, including a negative stiffness component but required a standing tip-link tension. In addition, this model suggests the mechanotransducer channel is most sensitive to curvature forces that are located within 2 nm of the tip-link. [Work supported in part by Grant Nos. R01-DC07910 and R01-DC03896 from the NIDCD of NIH and by The Timoshenko fund from Mechanical Engineering Department at Stanford University].

  View details for DOI 10.1121/1.4806258

  View details for PubMedID 23655592

• Three-dimensional distribution of transverse collagen fibers in the anterior human corneal stroma. Investigative ophthalmology & visual science Winkler, M., Shoa, G., Xie, Y., Petsche, S. J., Pinsky, P. M., Juhasz, T., Brown, D. J., Jester, J. V. 2013; 54 (12): 7293-7301

  Abstract

  Recent investigations of human corneal structure and biomechanics have shown that stromal collagen fibers (lamellae) are organized into a complex, highly intertwined three-dimensional meshwork of transverse oriented fibers that increases stromal stiffness and controls corneal shape. The purpose of this study was to characterize the three-dimensional distribution of transverse collagen fibers along the major meridians of the cornea using an automated method to rapidly quantify the collagen fibers' angular orientation.Three eyes from three donors were perfusion-fixed under pressure, excised, and cut into four quadrants. Quadrants were physically sectioned using a vibratome and scanned using nonlinear optical high-resolution macroscopy. Planes were analyzed numerically using software to identify collagen fiber angles relative to the corneal surface, stromal depth, and radial position within the anterior 250 μm of the stroma.The range of fiber angles and the fiber percentage having an angular displacement greater than ±3.5° relative to the corneal surface ("transverse fibers") was highest in the anterior stroma and decreased with depth. Numerical analysis showed no significant differences in fiber angles and transverse fibers between quadrants, meridians, and radial position.These results match our previous observation of a depth-dependent gradient in stromal collagen interconnectivity in the central cornea, and show that this gradient extends from the central cornea to the limbus. The lack of a preferred distribution of angled fibers with regard to corneal quadrant or radial position likely serves to evenly distribute loads and to avoid the formation of areas of stress concentration.

  View details for DOI 10.1167/iovs.13-13150

  View details for PubMedID 24114547

• Mechanisms of self-organization for the collagen fibril lattice in the human cornea. Journal of the Royal Society, Interface / the Royal Society Cheng, X., Pinsky, P. M. 2013; 10 (87): 20130512-?

  Abstract

  The transparency of the human cornea depends on the regular lattice arrangement of the collagen fibrils and on the maintenance of an optimal hydration-the achievement of both depends on the presence of stromal proteoglycans (PGs) and their linear sidechains of negatively charged glycosaminoglycans (GAGs). Although the GAGs produce osmotic pressure by the Donnan effect, the means by which they exert positional control of the lattice is less clear. In this study, a theoretical model based on equilibrium thermodynamics is used to describe restoring force mechanisms that may control and maintain the fibril lattice and underlie corneal transparency. Electrostatic-based restoring forces that result from local charge density changes induced by fibril motion, and entropic elastic restoring forces that arise from duplexed GAG structures that bridge neighbouring fibrils, are described. The model allows for the possibility that fibrils have a GAG-dense coating that adds an additional fibril force mechanism preventing fibril aggregation. Swelling pressure predictions are used to validate the model with results showing excellent agreement with experimental data over a range of hydration from 30 to 200% of normal. The model suggests that the electrostatic restoring force is dominant, with the entropic forces from GAG duplexes being an order or more smaller. The effect of a random GAG organization, as observed in recent imaging, is considered in a dynamic model of the lattice that incorporates randomness in both the spatial distribution of GAG charge and the topology of the GAG duplexes. A striking result is that the electrostatic restoring forces alone are able to reproduce the image-based lattice distribution function for the human cornea, and thus dynamically maintain the short-range order of the lattice.

  View details for DOI 10.1098/rsif.2013.0512

  View details for PubMedID 23904589

  View details for PubMedCentralID PMC3758012

• Depth-Dependent Transverse Shear Properties of the Human Corneal Stroma INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE Petsche, S. J., Chernyak, D., Martiz, J., Levenston, M. E., Pinsky, P. M. 2012; 53 (2): 873-880

  Abstract

  To measure the transverse shear modulus of the human corneal stroma and its profile through the depth by mechanical testing, and to assess the validity of the hypothesis that the shear modulus will be greater in the anterior third due to increased interweaving of lamellae.Torsional rheometry was used to measure the transverse shear properties of 6 mm diameter buttons of matched human cadaver cornea pairs. One cornea from each pair was cut into thirds through the thickness with a femtosecond laser and each stromal third was tested individually. The remaining intact corneas were tested to measure full stroma shear modulus. The shear modulus from a 1% shear strain oscillatory test was measured at various levels of axial compression for all samples.After controlling for axial compression, the transverse shear moduli of isolated anterior layers were significantly higher than central and posterior layers. Mean modulus values at 0% axial strain were 7.71 ± 6.34 kPa in the anterior, 1.99 ± 0.45 kPa in the center, 1.31 ± 1.01 kPa in the posterior, and 9.48 ± 2.92 kPa for full thickness samples. A mean equilibrium compressive modulus of 38.7 ± 8.6 kPa at 0% axial strain was calculated from axial compression measured during the shear tests.Transverse shear moduli are two to three orders of magnitude lower than tensile moduli reported in the literature. The profile of shear moduli through the depth displayed a significant increase from posterior to anterior. This gradient supports the hypothesis and corresponds to the gradient of interwoven lamellae seen in imaging of stromal cross-sections.

  View details for DOI 10.1167/iovs.11-8611

  View details for Web of Science ID 000302788600046

  View details for PubMedID 22205608

  View details for PubMedCentralID PMC3317426

• A nonlinear macroscopic multi-phasic model for describing interactions between solid, fluid and ionic species in biological tissue materials PHILOSOPHICAL MAGAZINE Li, L., Pinsky, P. M. 2011; 91 (2): 311-325

  View details for DOI 10.1080/14786435.2010.519353

  View details for Web of Science ID 000284540500008

• Elastostatic Analysis of the Membrane Tenting Deformation of Inner-Ear Stereocilia 11th International Workshop on the Mechanics of Hearing Kim, J., Pinsky, P. M., Ricci, A. J., Puria, S., Steele, C. R. AMER INST PHYSICS. 2011

  View details for DOI 10.1063/1.3658059

  View details for Web of Science ID 000301945200008

• Matrix-Pade via Lanczos solutions for vibrations of fluid-structure interaction INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Liew, H., Pinsky, P. M. 2010; 84 (10): 1183-1204

  View details for DOI 10.1002/nme.2936

  View details for Web of Science ID 000284204400003

• DEPTH DEPENDENT IN-PLANE SHEAR PROPERTIES OF THE CORNEAL STROMA 12th ASME Summer Bioengineering Conference Petsche, S., Pinsky, P., Chernyak, D., Martiz, J. AMER SOC MECHANICAL ENGINEERS. 2010: 397–398

  View details for Web of Science ID 000290705300199

• ELECTROSTATIC CONTRIBUTION OF THE PROTEOGLYCANS TO THE IN-PLANE SHEAR AND COMPRESSIVE STIFFNESS OF CORNEAL STROMA Hatami-Marbini, H., Pinsky, P. M., ASME AMER SOC MECHANICAL ENGINEERS. 2010: 369–70

  View details for Web of Science ID 000290705300185

• THE CONTRIBUTION OF PROTEOGLYCANS TO THE MECHANICAL PROPERTIES OF THE CORNEAL STROMA ASME 1st Global Congress on NanoEngineering for Medicine and Biology Hatami-Marbini, H., Pinsky, P. M. AMER SOC MECHANICAL ENGINEERS. 2010: 299–300

  View details for Web of Science ID 000282210100125

• Multiscale Modeling Framework of Transdermal Drug Delivery ANNALS OF BIOMEDICAL ENGINEERING Rim, J. E., Pinsky, P. M., van Osdol, W. W. 2009; 37 (6): 1217-1229

  Abstract

  This study addresses the modeling of transdermal diffusion of drugs to better understand the permeation of molecules through the skin, especially the stratum corneum, which forms the main permeation barrier to percutaneous permeation. In order to ensure reproducibility and predictability of drug permeation through the skin and into the body, a quantitative understanding of the permeation barrier properties of the stratum corneum (SC) is crucial. We propose a multiscale framework of modeling the multicomponent transdermal diffusion of molecules. The problem is divided into subproblems of increasing length scale: microscopic, mesoscopic, and macroscopic. First, the microscopic diffusion coefficient in the lipid bilayers of the SC is found through molecular dynamics (MD) simulations. Then, a homogenization procedure is performed over a model unit cell of the heterogeneous SC, resulting in effective diffusion parameters. These effective parameters are the macroscopic diffusion coefficients for the homogeneous medium that is "equivalent" to the heterogeneous SC, and thus can be used in finite element simulations of the macroscopic diffusion process. The resulting drug flux through the skin shows very reasonable agreement to experimental data.

  View details for DOI 10.1007/s10439-009-9678-1

  View details for Web of Science ID 000265787100015

  View details for PubMedID 19319682

• MODELING THE OPTICAL PERFORMANCE OF THE HUMAN CORNEA FOLLOWING REFRACTIVE SURGERY ASME Summer Bioengineering Conference Pinsky, P. M., van der Heide, D. AMER SOC MECHANICAL ENGINEERS. 2009: 777–778

  View details for Web of Science ID 000263364700389

• Modeling electrostatic force microscopy for conductive and dielectric samples using the boundary element method ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS Shen, Y., Barnett, D. M., Pinsky, P. M. 2008; 32 (8): 682-691

  View details for DOI 10.1016/j.enganabound.2007.12.003

  View details for Web of Science ID 000262890600007

• Finite element modeling of acousto-mechanical coupling in the cat middle ear JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA Tuck-Lee, J. P., Pinsky, P. M., Steele, C. R., Puria, S. 2008; 124 (1): 348-362

  Abstract

  The function of the middle ear is to transfer acoustic energy from the ear canal to the cochlea. An essential component of this system is the tympanic membrane. In this paper, a new finite element model of the middle ear of the domestic cat is presented, generated in part from cadaver anatomy via microcomputed tomographic imaging. This model includes a layered composite model of the eardrum, fully coupled with the acoustics in the ear canal and middle-ear cavities. Obtaining the frequency response from 100 Hz to 20 kHz is a computationally challenging task, which has been accomplished by using a new adaptive implementation of the reduced-order matrix Padé-via-Lanczos algorithm. The results are compared to established physiological data. The fully coupled model is applied to study the role of the collagen fiber sublayers of the eardrum and to investigate the relationship between the structure of the middle-ear cavities and its function. Three applications of this model are presented, demonstrating the shift in the middle-ear resonance due to the presence of the septum that divides the middle-ear cavity space, the significance of the radial fiber layer on high frequency transmission, and the importance of the transverse shear modulus in the eardrum microstructure.

  View details for DOI 10.1121/1.2912438

  View details for Web of Science ID 000257768000034

  View details for PubMedID 18646982

  View details for PubMedCentralID PMC2677330

• Analytic perturbation solution to the capacitance system of a hyberboloidal tip and a rough surface APPLIED PHYSICS LETTERS Shen, Y., Barnett, D. M., Pinsky, P. M. 2008; 92 (13)

  View details for DOI 10.1063/1.2906487

  View details for Web of Science ID 000254669900117

• Simulating and interpreting Kelvin probe force microscopy images on dielectrics with boundary integral equations REVIEW OF SCIENTIFIC INSTRUMENTS Shen, Y., Barnett, D. M., Pinsky, P. M. 2008; 79 (2)

  Abstract

  Kelvin probe force microscopy (KPFM) is designed for measuring the tip-sample contact potential differences by probing the sample surface, measuring the electrostatic interaction, and adjusting a feedback circuit. However, for the case of a dielectric (insulating) sample, the contact potential difference may be ill defined, and the KPFM probe may be sensing electrostatic interactions with a certain distribution of sample trapped charges or dipoles, leading to difficulty in interpreting the images. We have proposed a general framework based on boundary integral equations for simulating the KPFM image based on the knowledge about the sample charge distributions (forward problem) and a deconvolution algorithm solving for the trapped charges on the surface from an image (inverse problem). The forward problem is a classical potential problem, which can be efficiently solved using the boundary element method. Nevertheless, the inverse problem is ill posed due to data incompleteness. For some special cases, we have developed deconvolution algorithms based on the forward problem solution. As an example, this algorithm is applied to process the KPFM image of a gadolinia-doped ceria thin film to solve for its surface charge density, which is a more relevant quantity for samples of this kind than the contact potential difference (normally only defined for conductive samples) values contained in the raw image.

  View details for DOI 10.1063/1.2885679

  View details for Web of Science ID 000254194400034

  View details for PubMedID 18315309

• Adaptive frequency windowing for multifrequency solutions in structural acoustics based on the matrix Pade-via-Lanczos algorithm INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Tuck-Lee, J. P., Pinsky, P. M. 2008; 73 (5): 728-746

  View details for DOI 10.1002/nme.2102

  View details for Web of Science ID 000253694000007

• A resolution study for electrostatic force microscopy on bimetallic samples using the boundary element method NANOTECHNOLOGY Shen, Y., Lee, M., Lee, W., Barnett, D. M., Pinsky, P., Prinz, F. B. 2008; 19 (3)

  Abstract

  Electrostatic force microscopy (EFM) is a special design of non-contact atomic force microscopy used for detecting electrostatic interactions between the probe tip and the sample. Its resolution is limited by the finite probe size and the long-range characteristics of electrostatic forces. Therefore, quantitative analysis is crucial to understanding the relationship between the actual local surface potential distribution and the quantities obtained from EFM measurements. To study EFM measurements on bimetallic samples with surface potential inhomogeneities as a special case, we have simulated such measurements using the boundary element method and calculated the force component and force gradient component that would be measured by amplitude modulation (AM) EFM and frequency modulation (FM) EFM, respectively. Such analyses have been performed for inhomogeneities of various shapes and sizes, for different tip-sample separations and tip geometries, for different applied voltages, and for different media (e.g., vacuum or water) in which the experiment is performed. For a sample with a surface potential discontinuity, the FM-EFM resolution expression agrees with the literature; however, the simulation for AM-EFM suggests the existence of an optimal tip radius of curvature in terms of resolution. On the other hand, for samples with strip- and disk-shaped surface potential inhomogeneities, we have obtained quantitative expressions for the detectability size requirements as a function of experimental conditions for both AM- and FM-EFMs, which suggest that a larger tip radius of curvature is moderately favored for detecting the presence of such inhomogeneities.

  View details for DOI 10.1088/0957-4484/19/03/035710

  View details for PubMedID 21817595

• Using the method of homogenization to calculate the effective diffusivity of the stratum corneum with permeable corneocytes JOURNAL OF BIOMECHANICS Rim, J. E., Pinsky, P. M., van Osdol, W. W. 2008; 41 (4): 788-796

  Abstract

  The stratum corneum is the outermost layer of the skin, which acts as a barrier membrane against the penetration of molecules into and out of the body. It has a biphasic structure consisting of keratinized cells (corneocytes) that are embedded in a lipid matrix. The macroscopic transport properties of the stratum corneum are functions of its microstructure and the transport properties of the corneocytes and the lipid matrix, and are of considerable interest in the context of transdermal drug delivery and quantifying exposure to toxins, as well as for determining the relation of skin disorders to disruption of the stratum corneum barrier. Due to the complexity of the tissue and the difference in length scales involved in its microstructure, a direct analysis of the mass transport properties of the stratum corneum is not feasible. In this study, we undertake an approach where the macroscopic diffusion tensor of the stratum corneum is obtained through homogenization using the method of asymptotic expansions. The biphasic structure of the stratum corneum is fully accounted for by allowing the corneocytes to be permeable and considering the partitioning between the corneocytes and the lipid phases. By systematically exploring the effect of permeable corneocytes on the macroscopic transport properties of the stratum corneum, we show that solute properties such as lipophilicity and relative permeabilities in the two phases have large effects on its transdermal diffusion behavior.

  View details for DOI 10.1016/j.jbiomech.2007.11.011

  View details for Web of Science ID 000254677400008

  View details for PubMedID 18093598

• Integral equation modeling of electrostatic interactions in atomic force microscopy International Conference on Integral Methods in Science and Engineering (IMSE 2006) Shen, Y., Barnett, D. M., Pinsky, P. M. BIRKHAUSER BOSTON. 2008: 237–246

  View details for Web of Science ID 000252056300027

• Using the method of homogenization to calculate the effective diffusivity of the stratum corneum JOURNAL OF MEMBRANE SCIENCE Rim, J. E., Pinsky, P. M., van Osdol, W. W. 2007; 293 (1-2): 174-182

  View details for DOI 10.1016/j.memsci.2007.02.018

  View details for Web of Science ID 000245971600020

• Finite element modeling of coupled diffusion with partitioning in transdermal drug delivery ANNALS OF BIOMEDICAL ENGINEERING Rim, J. E., PINSKY, P. M., van Osdol, W. W. 2005; 33 (10): 1422-1438

  Abstract

  The finite element method is employed to simulate two-dimensional (axisymmetric) drug diffusion from a finite drug reservoir into the skin. The numerical formulation is based on a general mathematical model for multicomponent nonlinear diffusion that takes into account the coupling effects between the different components. The presence of several diffusing components is crucial, as many transdermal drug delivery formulations contain one or more permeation enhancers in addition to the drug. The coupling between the drug and permeation enhancer(s) results in nonlinear diffusion with concentration-dependent diffusivities of the various components. The framework is suitable for modeling both linear and nonlinear, single- and multicomponent diffusions, however, as it reduces to the correct formulation simply by setting the relevant parameters to zero. In addition, we show that partitioning of the penetrants from the reservoir into the skin can be treated in a straightforward manner in this framework using the mixed method. Partitioning at interface boundaries poses some difficulty with the standard finite element method as it creates a discontinuity in the concentration variable at the interface. To our knowledge, nonlinear (concentration-dependent) partitioning in diffusion problems has not been treated numerically before, and we demonstrate that nonlinear partitioning may have an important role in the effect of permeation enhancers. The mixed method that we adopt includes the flux at the interface explicitly in the formulation, allowing the modeling of concentration-dependent partitioning of the permeants between the reservoir and the skin as well as constant (linear) partitioning. The result is a versatile finite element framework suitable for modeling both linear and nonlinear diffusions in heterogeneous media where the diffusivities and partition coefficients may vary in each subregion.

  View details for DOI 10.1007/s10439-005-5788-6

  View details for Web of Science ID 000232758300012

  View details for PubMedID 16240090

• A 3D model of muscle reveals the causes of nonuniform strains in the biceps brachii JOURNAL OF BIOMECHANICS Blemker, S. S., PINSKY, P. M., Delp, S. L. 2005; 38 (4): 657-665

  Abstract

  Biomechanical models generally assume that muscle fascicles shorten uniformly. However, dynamic magnetic resonance (MR) images of the biceps brachii have recently shown nonuniform shortening along some muscle fascicles during low-load elbow flexion (J. Appl. Physiol. 92 (2002) 2381). The purpose of this study was to uncover the features of the biceps brachii architecture and material properties that could lead to nonuniform shortening. We created a three-dimensional finite-element model of the biceps brachii and compared the tissue strains predicted by the model with experimentally measured tissue strains. The finite-element model predicted strains that were within one standard deviation of the experimentally measured strains. Analysis of the model revealed that the variation in fascicle lengths within the muscle and the curvature of the fascicles were the primary factors contributing to nonuniform strains. Continuum representations of muscle, combined with in vivo image data, are needed to deepen our understanding of how complex geometric arrangements of muscle fibers affect muscle contraction mechanics.

  View details for DOI 10.1016/j.jbiomech.2004.04.009

  View details for Web of Science ID 000227590400002

  View details for PubMedID 15713285

• Recovery of shear modulus in elastography using an ajoint method with B-spline representation FINITE ELEMENTS IN ANALYSIS AND DESIGN Liew, H. L., Pinsky, P. M. 2005; 41 (7-8): 778-799

  View details for DOI 10.1016/j.finel.2004.10.009

  View details for Web of Science ID 000228126000006

• A molecular dynamics study of the diffusion of fentanyl in DPPC bilayers 49th Annual Meeting of the Biophysical-Society Rim, J. E., PINSKY, P. M., van Osdol, W. W. CELL PRESS. 2005: 148A–148A

  View details for Web of Science ID 000226378500717

• Computational modeling of mechanical anisotropy in the cornea and sclera JOURNAL OF CATARACT AND REFRACTIVE SURGERY Pinsky, P. M., van der Heide, D., Chernyak, D. 2005; 31 (1): 136-145

  Abstract

  To determine the biomechanical deformation of the cornea resulting from tissue cutting and removal by use of a new computational model and to investigate the effect of mechanical anisotrophy resulting from the fibrillar architecture.Department of Mechanical Engineering, Stanford University, Stanford, California, USA.A mathematical model for a typical lamella that explicitly accounts for the strain energy of the collagen fibrils, extrafibrillar matrix, and proteoglycan cross-linking was developed. A stromal model was then obtained by generalized averaging of the lamella properties through the stromal thickness, taking into account the preferred orientations of the collagen fibrils, which were obtained from x-ray scattering data.The model was used to predict astigmatism induced by a tunnel incision in the sclera, such as is used for cataract extraction and intraocular lens implantation. The amount of induced cylinder was in good agreement with published clinical data. Results show it is important for the model to incorporate preexisting corneal physiological stress caused by intraocular pressure.The mathematical model described appears to provide a framework for further development, capturing the essential features of mechanical anisotropy of the cornea. The tunnel incision simulation indicated the importance of the anisotropy in this case.

  View details for DOI 10.1016/j.jcrs.2004.10.048

  View details for Web of Science ID 000227227000031

  View details for PubMedID 15721706

• An application of shape optimization in the solution of inverse acoustic scattering problems INVERSE PROBLEMS Feijoo, G. R., Oberai, A. A., PINSKY, P. M. 2004; 20 (1): 199-228

  View details for DOI 10.1088/0266-5611/20/1/012

  View details for Web of Science ID 000220062200012

• A Krylov subspace projection method for simultaneous solution of Helmholtz problems at multiple frequencies COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Wagner, M. M., PINSKY, P. M., Oberai, A. A., Malhotra, M. 2003; 192 (41-42): 4609-4640

  View details for DOI 10.1016/S0045-7825(03)00429-8

  View details for Web of Science ID 000185690100005

• Application of Pade via Lanczos approximations for efficient multifrequency solution of Helmholtz problems JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA Wagner, M. M., PINSKY, P. M., Malhotra, M. 2003; 113 (1): 313-319

  Abstract

  This paper addresses the efficient solution of acoustic problems in which the primary interest is obtaining the solution only on restricted portions of the domain but over a wide range of frequencies. The exterior acoustics boundary value problem is approximated using the finite element method in combination with the Dirichlet-to-Neumann (DtN) map. The restriction domain problem is formally posed in transfer function form based on the finite element solution. In order to obtain the solution over a range of frequencies, a matrix-valued Padé approximation of the transfer function is employed, using a two-sided block Lanczos algorithm. This approach provides a stable and efficient representation of the Padé approximation. In order to apply the algorithm, it is necessary to reformulate the transfer function due to the frequency dependency in the nonreflecting boundary condition. This is illustrated for the case of the DtN boundary condition, but there is no restriction on the approach which can also be applied to other radiation boundary conditions. Numerical tests confirm that the approach offers significant computational speed-up.

  View details for DOI 10.1121/1.1514932

  View details for PubMedID 12558270

• Computational investigation of the biomechanical response of the cornea to lamellar procedures. Guarnieri, F. A., PINSKY, P. M., Shimmick, J. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2001: S603–S603

  View details for Web of Science ID 000168392103201

• Shape sensitivity calculations for exterior acoustics problems ENGINEERING COMPUTATIONS Feijoo, G. R., Malhotra, M., Oberai, A. A., PINSKY, P. M. 2001; 18 (3-4): 376-391

  View details for Web of Science ID 000169484700003

• A residual-based finite element method for the Helmholtz equation INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Oberai, A. A., PINSKY, P. M. 2000; 49 (3): 399-419

  View details for Web of Science ID 000089154200003

• A numerical comparison of finite element methods for the Helmholtz equation JOURNAL OF COMPUTATIONAL ACOUSTICS Oberai, A. A., PINSKY, P. M. 2000; 8 (1): 211-221

  View details for Web of Science ID 000087133200013

• Efficient computation of multi-frequency far-field solutions of the Helmholtz equation using Pade approximation JOURNAL OF COMPUTATIONAL ACOUSTICS Malhotra, M., PINSKY, P. M. 2000; 8 (1): 223-240

  View details for Web of Science ID 000087133200014

• A novel method to utilize existing TCAD tools to build accurate geometry required for MEMS simulation 2nd International Conference on Modeling and Simulation of Microsystems Wilson, N. M., Liang, S., PINSKY, P. M., DUTTON, R. W. COMPUTATIONAL PUBLICATIONS. 1999: 120–123

  View details for Web of Science ID 000222851500030

• Investigation of tetrahedral automatic mesh generation for finite-element simulation of micro-electro-mechanical switches 2nd International Conference on Modeling and Simulation of Microsystems Wilson, N. M., PINSKY, P. M., DUTTON, R. W. COMPUTATIONAL PUBLICATIONS. 1999: 305–308

  View details for Web of Science ID 000222851500075

• On the implementation of the Dirichlet-to-Neumann radiation condition for iterative solution of the Helmholtz equation APPLIED NUMERICAL MATHEMATICS Oberai, A. A., Malhotra, M., PINSKY, P. M. 1998; 27 (4): 443-464

  View details for Web of Science ID 000075199100008

• Parallel preconditioning based on h-hierarchical finite elements with application to acoustics COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Malhotra, M., PINSKY, P. M. 1998; 155 (1-2): 97-117

  View details for Web of Science ID 000073170300006

• Galerkin Generalized Least Squares finite element methods for time-harmonic structural acoustics COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Grosh, K., PINSKY, P. M. 1998; 154 (3-4): 299-318

  View details for Web of Science ID 000072962900009

• A multiscale finite element method for the Helmholtz equation COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Oberai, A. A., PINSKY, P. M. 1998; 154 (3-4): 281-297

  View details for Web of Science ID 000072962900008

• Finite element modeling for interconnect materials and structures Symposium on Advanced Interconnects and Contact Materials and Processes for Future Integrated Circuits Bassman, L., Pinsky, P., Deal, M. MATERIALS RESEARCH SOCIETY. 1998: 299–299

  View details for Web of Science ID 000077430000049

• Iterative solution of multiple radiation and scattering problems in structural acoustics using a block quasi-minimal residual algorithm COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Malhotra, M., Freund, R. W., PINSKY, P. M. 1997; 146 (1-2): 173-196

  View details for Web of Science ID A1997XD81900010

• Nonlinear dynamic modeling of micromachined microwave switches 41st Annual IEEE MTT-Society International Microwave Symposium (IMS) at 1997 Microwave Week Chang, E. K., Kan, E. C., DUTTON, R. W., PINSKY, P. M. IEEE. 1997: 1511–1514

  View details for Web of Science ID A1997BH95V00353

• Mesoscale modeling of diffusion in polycrystalline structures 1997 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD 97) BASSMAN, L. C., Ibrahim, N. R., PINSKY, P. M., Saraswat, K. C., Deal, M. D. IEEE. 1997: 149–152

  View details for Web of Science ID A1997BJ53T00037

• A matrix-free interpretation of the non-local Dirichlet-to-Neumann radiation boundary condition INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Malhotra, M., PINSKY, P. M. 1996; 39 (21): 3705-3713

  View details for Web of Science ID A1996VP81100007

• Stabilized Element Residual Method (SERM): A posteriori error estimation for the advection-diffusion equation JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS Agarwal, A. N., PINSKY, P. M. 1996; 74 (1-2): 3-17

  View details for Web of Science ID A1996VT30900002

• A space-time finite element method for structural acoustics in infinite domains .2. Exact time-dependent non-reflecting boundary conditions COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Thompson, L. L., PINSKY, P. M. 1996; 132 (3-4): 229-258

  View details for Web of Science ID A1996UX23500003

• A space-time finite element method for the exterior acoustics problem JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA Thompson, L. L., PINSKY, P. M. 1996; 99 (6): 3297-3311

  View details for Web of Science ID A1996UQ66900002

• A space-time finite element method for structural acoustics in infinite domains .1. Formulation, stability and convergence COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Thompson, L. L., PINSKY, P. M. 1996; 132 (3-4): 195-227

  View details for Web of Science ID A1996UX23500002

• A space-time finite element method for the exterior structural acoustics problem: Time-dependent radiation boundary conditions in two space dimensions INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Thompson, L. L., PINSKY, P. M. 1996; 39 (10): 1635-?

  View details for Web of Science ID A1996UJ90300002

• Design of Galerkin Generalized Least Squares methods for Timoshenko beams COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Grosh, K., PINSKY, P. M. 1996; 132 (1-2): 1-16

  View details for Web of Science ID A1996UW38200001

• Finite element modelling of intravitreous drug kinetics PINSKY, P. M., Maurice, D. M., DATYE, D. V. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 1996: 3200–3200

  View details for Web of Science ID A1996TX39703196

• Numerical prediction of astigmatic corrections in the human cornea after insertion of intrastromal corneal ring arcs DATYE, D. V., PINSKY, P. M., Silvestrini, T. A. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 1996: 310–10

  View details for Web of Science ID A1996TX39700309

• Numerical simulation of glucose diffusion in the cornea with an ICR(R) (intrastromal corneal ring) Silvestrini, T. A., PINSKY, P. M., DATYE, D. V. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 1996: 311–11

  View details for Web of Science ID A1996TX39700310

• A Finite element method for the Helmholtz equation based on a subgrid scale model 2nd ECCOMAS Conference on Numerical Methods in Engineering Oberai, A. A., PINSKY, P. M. JOHN WILEY & SONS LTD. 1996: 79–85

  View details for Web of Science ID A1996BJ05Y00013

• NUMERICAL-SOLUTION OF 2-CARRIER HYDRODYNAMIC SEMICONDUCTOR-DEVICE EQUATIONS EMPLOYING A STABILIZED FINITE-ELEMENT METHOD COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Aluru, N. R., Law, K. H., Raefsky, A., PINSKY, P. M., DUTTON, R. W. 1995; 125 (1-4): 187-220

  View details for Web of Science ID A1995RU66800011

• An analysis of the hydrodynamic semiconductor device model - Boundary conditions and simulations COMPEL-THE INTERNATIONAL JOURNAL FOR COMPUTATION AND MATHEMATICS IN ELECTRICAL AND ELECTRONIC ENGINEERING Aluru, N. R., Law, K. H., PINSKY, P. M., DUTTON, R. W. 1995; 14 (2-3): 157-185

  View details for Web of Science ID A1995TW93900009

• NUMERICAL-SIMULATION OF SURGICAL-PROCEDURES ON THE HUMAN CORNEA USING MECHANICAL MODELS BASED ON CORNEAL ULTRA-STRUCTURE DATYE, D. V., PINSKY, P. M. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 1995: S38–S38

  View details for Web of Science ID A1995QM91500178

• NUMERICAL-SIMULATION OF TOPOGRAPHICAL ALTERATIONS IN THE CORNEA AFTER ICR(R) (INTRASTROMAL CORNEAL RING) PINSKY, P. M., DATYE, D. V., Silvestrini, T. A. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 1995: S309–S309

  View details for Web of Science ID A1995QM91501439

• A GALERKIN LEAST-SQUARES FINITE-ELEMENT METHOD FOR THE 2-DIMENSIONAL HELMHOLTZ-EQUATION INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Thompson, L. L., PINSKY, P. M. 1995; 38 (3): 371-397

  View details for Web of Science ID A1995QE24900002

• FINITE-ELEMENT FORMULATION FOR A BAFFLED, FLUID-LOADED, FINITE CYLINDRICAL-SHELL Symposium on Computational Structural Acoustics, at the 2nd US National Congress on Computational Mechanics Grosh, K., PINSKY, P. M., Malhotra, M., Rao, V. S. JOHN WILEY & SONS LTD. 1994: 2971–85

  View details for Web of Science ID A1994PG38500007

• SELECTED PAPERS FROM THE SYMPOSIUM ON COMPUTATIONAL STRUCTURAL ACOUSTICS, 2ND UNITED-STATES-NATIONAL-CONGRESS ON COMPUTATIONAL MECHANICS - PREFACE INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING PINSKY, P. M. 1994; 37 (17): 2891-2891

  View details for Web of Science ID A1994PG38500001

• DETERMINATION OF MECHANICAL-PROPERTIES OF CORNEA IN-VIVO BY INDENTATION Chang, S. S., Maurice, D. M., PINSKY, P. M., DATYE, D. V. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 1994: 1357–57

  View details for Web of Science ID A1994MZ58500475

• A MICROSTRUCTURALLY-BASED MECHANICAL MODEL OF THE HUMAN CORNEA WITH APPLICATION TO KERATOTOMY PINSKY, P. M., DATYE, D. V. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 1994: 1296–96

  View details for Web of Science ID A1994MZ58500204

• COMPLEX WAVE-NUMBER DISPERSION ANALYSIS OF GALERKIN AND GALERKIN LEAST-SQUARES METHODS FOR FLUID-LOADED PLATES COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Grosh, K., PINSKY, P. M. 1994; 113 (1-2): 67-98

  View details for Web of Science ID A1994NC69700005

• SPACE-TIME GALERKIN LEAST-SQUARES FINITE-ELEMENT FORMULATION FOR THE HYDRODYNAMIC DEVICE EQUATIONS 1993 VLSI Process and Device Modeling Workshop (VPAD 93) Aluru, N. R., Law, K. H., PINSKY, P. M., Raefsky, A., GOOSSENS, R. J., DUTTON, R. W. IEICE-INST ELECTRON INFO COMMUN ENG. 1994: 227–35

  View details for Web of Science ID A1994MY97500023

• COMPLEX WAVE-NUMBER FOURIER-ANALYSIS OF THE P-VERSION FINITE-ELEMENT METHOD COMPUTATIONAL MECHANICS Thompson, L. L., PINSKY, P. M. 1994; 13 (4): 255-275

  View details for Web of Science ID A1994NZ13700003

• A SPACE-TIME FINITE ELEMENT METHOD FOR FLUID STRUCTURE INTERACTION IN EXTERIOR DOMAINS 2nd International Conference on Computational Structures Technology PINSKY, P. M., Thompson, L. L. CIVIL COMP PRESS. 1994: 103–115

  View details for Web of Science ID A1994BC38P00012

• GALERKIN GENERALIZED LEAST SQUARES METHODS FOR INVACUO AND FLUID-LOADED TIMOSHENKO BEAMS Conference on Recent Developments in Finite Element Analysis, in honor of Robert L Taylor on his 60th Birthday PINSKY, P. M., Grosh, K. INT CENTER NUMERICAL METHODS ENGINEERING. 1994: 47–61

  View details for Web of Science ID A1994BC63C00004

• A FINITE-ELEMENT FORMULATION FOR THE HYDRODYNAMIC SEMICONDUCTOR-DEVICE EQUATIONS COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Aluru, N. R., Raefsky, A., PINSKY, P. M., Law, K. H., GOOSSENS, R. J., DUTTON, R. W. 1993; 107 (1-2): 269-298

  View details for Web of Science ID A1993LR19300015

• CORNEAL DEFORMATION BY INDENTATION AND APPLANATION FORCES Chang, S. S., Hjortdal, J. O., Maurice, D. M., PINSKY, P. M. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 1993: 1241–41

  View details for Web of Science ID A1993KT89302637

• NEW GENERALIZED GALERKIN LEAST-SQUARES FINITE-ELEMENT METHODS FOR WAVE-PROPAGATION IN TIMOSHENKO BEAMS 2ND INTERNATIONAL CONF ON MATHEMATICAL AND NUMERICAL ASPECTS OF WAVE PROPAGATION Grosh, K., PINSKY, P. M. SIAM. 1993: 237–245

  View details for Web of Science ID A1993BY70Y00025

• FINITE-ELEMENT DISPERSION ANALYSIS FOR THE 3-DIMENSIONAL 2ND-ORDER SCALAR WAVE-EQUATION INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING ABBOUD, N. N., PINSKY, P. M. 1992; 35 (6): 1183-1218

  View details for Web of Science ID A1992JQ75400003

• Numerical modeling of radial, astigmatic, and hexagonal keratotomy. Refractive and corneal surgery PINSKY, P. M., DATYE, D. V. 1992; 8 (2): 164-172

  Abstract

  A mechanical model of the human cornea is proposed and employed in a finite element formulation for simulating the effects of keratotomy on the cornea.The formulation assumes that the structural behavior of the cornea is governed by the properties of the stroma which is modeled as a thick membrane. The tensile forces in the cornea are resisted by the collagen fibrils embedded in the ground substance of the stromal lamellae. When the stromal lamellae are cut, as in keratotomy, it is assumed that they no longer carry any tensile forces, and the forces in the cornea are then resisted only by the remaining uncut lamellae. A constitutive model, which represents the anisotropy and inhomogeneity in the membrane rigidity induced by the incisions, has been employed in a geometrically nonlinear finite element membrane formulation for small strains with moderate rotations. This preliminary model is restricted to linear material behavior with no time dependency.A number of numerical examples are presented to illustrate the effectiveness of the proposed constitutive model and the finite element formulation for computing the immediate postoperative shift in corneal power resulting from radial, astigmatic, and hexagonal keratotomy. Surgical changes computed using the proposed model compare well with surgical corrections predicted by expert surgeons.The proposed computational model of the cornea and the effects of surgical procedures on it is based on a number of important simplifying assumptions regarding the mechanical properties and structure of the corneal tissue at the ultrastructure level. The encouraging results found with present model suggest that further development and refinement will be useful.

  View details for PubMedID 1591212

• LOCAL HIGH-ORDER RADIATION BOUNDARY-CONDITIONS FOR THE 2-DIMENSIONAL TIME-DEPENDENT STRUCTURAL ACOUSTICS PROBLEM JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA PINSKY, P. M., Thompson, L. L., ABBOUD, N. N. 1992; 91 (3): 1320-1335

  View details for Web of Science ID A1992HH96500011

• FINITE-ELEMENT SOLUTION OF THE TRANSIENT EXTERIOR STRUCTURAL ACOUSTICS PROBLEM BASED ON THE USE OF RADIALLY ASYMPTOTIC BOUNDARY OPERATORS COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING PINSKY, P. M., ABBOUD, N. N. 1991; 85 (3): 311-348

  View details for Web of Science ID A1991FB24200003

• A MICROSTRUCTURALLY-BASED FINITE-ELEMENT MODEL OF THE INCISED HUMAN CORNEA JOURNAL OF BIOMECHANICS PINSKY, P. M., DATYE, D. V. 1991; 24 (10): 907-922

  Abstract

  A mechanical model of the human cornea is proposed and employed in a finite element formulation for simulating the effects of surgical procedures, such as radial keratotomy, on the cornea. The model assumes that the structural behavior of the cornea is governed by the properties of the stroma. Arguments based on the microstructural organization and properties of the stroma lead to the conclusion that the human cornea exhibits flexural and shear rigidities which are negligible compared to its membrane rigidity. Accordingly, it is proposed that to a first approximation, the structural behavior of the cornea is that of a thick membrane shell. The tensile forces in the cornea are resisted by very fine collagen fibrils embedded in the ground substance of the stromal lamellae. When the collagen fibrils are cut, as in radial keratotomy, it is argued that they become relaxed since there is negligible transfer of load between adjacent fibrils due to the low shear modulus of the ground substance. The forces in the cornea are then resisted only by the remaining uncut fibrils. The cutting of fibrils induces an anisotropy and inhomogeneity in the membrane rigidity. By assuming a uniform angular distribution of stromal lamellae through the corneal thickness, geometric arguments lead to a quantitative representation for the anisotropy and inhomogeneity. All material behavior is assumed to be in the linear elastic regime and with no time-dependency. The resulting constitutive model for the incised cornea has been employed in a geometrically non-linear finite element membrane shell formulation for small strains with moderate rotations. A number of numerical examples are presented to illustrate the effectiveness of the proposed constitutive model and finite element formulation. The dependence of the outcome of radial keratotomy, measured in terms of the immediate postoperative shift in corneal power, on a number of important factors is investigated. These factors include the value of the elastic moduli of the stromal lamellae (dependent on the patient's age), the incision depth, the optic zone size, the number of incisions and their positions, and the intraocular pressure. Results have also been compared with expected surgical corrections predicted by three expert surgeons and show an excellent correspondence.

  View details for Web of Science ID A1991GK60000004

  View details for PubMedID 1744149

• ON THE USE OF LAGRANGE MULTIPLIER COMPATIBLE MODES FOR CONTROLLING ACCURACY AND STABILITY OF MIXED SHELL FINITE-ELEMENTS COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING PINSKY, P. M., JASTI, R. V. 1991; 85 (2): 151-182

  View details for Web of Science ID A1991EX18000002

• TRANSIENT FINITE-ELEMENT ANALYSIS OF THE EXTERIOR STRUCTURAL ACOUSTICS PROBLEM JOURNAL OF VIBRATION AND ACOUSTICS-TRANSACTIONS OF THE ASME PINSKY, P. M., ABBOUD, N. N. 1990; 112 (2): 245-256

  View details for Web of Science ID A1990EG37900013

• A MIXED FINITE-ELEMENT FORMULATION FOR REISSNER-MINDLIN PLATES BASED ON THE USE OF BUBBLE FUNCTIONS INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING PINSKY, P. M., JASTI, R. V. 1989; 28 (7): 1677-1702

  View details for Web of Science ID A1989AF61200013

• 2 MIXED VARIATIONAL-PRINCIPLES FOR EXTERIOR FLUID STRUCTURE INTERACTION PROBLEMS COMPUTERS & STRUCTURES PINSKY, P. M., ABBOUD, N. N. 1989; 33 (3): 621-635

  View details for Web of Science ID A1989CA63900002

• ELASTOPLASTIC SHELL ELEMENT BASED ON ASSUMED COVARIANT STRAIN INTERPOLATIONS JOURNAL OF ENGINEERING MECHANICS-ASCE PINSKY, P. M., Jang, J. 1988; 114 (6): 1045-1062

  View details for Web of Science ID A1988N535800008

• CONVERGENCE OF CURVED SHELL ELEMENTS BASED ON ASSUMED COVARIANT STRAIN INTERPOLATIONS INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Jang, J. H., PINSKY, P. M. 1988; 26 (2): 329-347

  View details for Web of Science ID A1988M079300003

• AN ASSUMED COVARIANT STRAIN BASED 9-NODE SHELL ELEMENT INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Jang, J. H., PINSKY, P. M. 1987; 24 (12): 2389-2411

  View details for Web of Science ID A1987L010300010

• A FINITE-ELEMENT FORMULATION FOR ELASTOPLASTICITY BASED ON A 3-FIELD VARIATIONAL EQUATION COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING PINSKY, P. M. 1987; 61 (1): 41-60

  View details for Web of Science ID A1987G417600002

• A MULTI-DIRECTOR FORMULATION FOR ELASTIC VISCOELASTIC LAYERED SHELLS INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING PINSKY, P. M., Kim, K. O. 1986; 23 (12): 2213-2244

  View details for Web of Science ID A1986F346900004

• A MULTI-DIRECTOR FORMULATION FOR NONLINEAR ELASTIC VISCOELASTIC LAYERED SHELLS COMPUTERS & STRUCTURES PINSKY, P. M., Kim, K. O. 1986; 24 (6): 901-913

  View details for Web of Science ID A1986F529000007

• COMPUTER ASSISTED TEST CONSTRUCTION - EFFORT BASED ON AN EVALUATION METHODOLOGY EDUCATIONAL TECHNOLOGY OREILLY, R. P., GORTH, W. P., Pinsky, P. 1973; 13 (3): 32-34

  View details for Web of Science ID A1973P200600015