Nicholas A. Peppas

Bio: Nicholas A. Peppas is an academic researcher from University of Texas at Austin. The author has contributed to research in topics: Self-healing hydrogels & Drug delivery. The author has an hindex of 141, co-authored 825 publications receiving 90533 citations. Previous affiliations of Nicholas A. Peppas include National Technical University & University of Texas System.

Modeling of penetrant diffusion in glassy polymers with an integral sorption deborah number

Abstract: A mathematical model was developed to explain the anomalous penetrant diffusion behavior in glassy polymers The model equations were derived by using the linear irreversible thermodynamics theory and the kinematic relations in continuum mechanics, showing the coupling between the polymer mechanical behavior and penetrant transport The Maxwell model was used as the stress–strain constitutive equation, from which the polymer relaxation time was defined An integral sorption Deborah number was proposed as the ratio of the characteristic relaxation time in the glassy region to the characteristic diffusion time in the swollen region With this definition, an integral sorption process was characterized by a single Deborah number and the controlling mechanism was identified in terms of the value of the Deborah number The model equations were two coupled nonlinear differential equations A finite difference method was developed for solving the model equations Numerical simulation of integral sorption of penetrants in glassy polymers was performed The simulation results show that (1) the present model can predict Case II transport behavior as well as the transition from Case II to Fickian diffusion and (2) the integral sorption Deborah number is a major parameter affecting the transition © 1993 John Wiley & Sons, Inc

pH-Sensitive hydrogels as gastrointestinal tract absorption enhancers: transport mechanisms of salmon calcitonin and other model molecules using the Caco-2 cell model.

Abstract: The main interest of this work was the investigation of the transport mechanisms of salmon calcitonin through the epithelial cell monolayer in the presence and absence of pH-sensititive hydrogel nanospheres composed of poly(methacrylic acid-graftedpoly(ethylene glycol)) (PMAA-g-EG). For this purpose, a gastrointestinal cell culture model, the Caco-2 cell line, was employed. The transport of other macromolecules such as fluorescein sodium, fluorescein isothiocyanate dextran, and 14 C-mannitol were also investigated and compared. Transport experiments were conducted in the apical-tobasolateral direction at 37 and 5 °C and from the basolateral-to-apical direction at 37 °C. Results revealed that the presence of P(MAA-g-EG) nanospheres increased the transport of paracellularly transported molecules such as 14 C-mannitol and fluorescein isothiocyanate dextran when compared to controls. Fluorescein sodium salt solutions were investigated as an actively transported molecule. The transport of fluorescein was affected by the concentration of PEG chains in the structure. Salmon calcitonin transport was enhanced in the presence of the nanospheres. The comparison of the transport behavior of dextran and calcitonin revealed that the main transport mechanism for salmon calcitonin through epithelial cell monolayers is predominantly paracellular.

Models of Moisture Transport and Moisture-Induced Stresses in Epoxy Composites

Abstract: Mathematical models are presented to describe moisture transport in epoxy composites using concentration and stress dependent diffusion coefficients. These models take into consideration the stresses induced due to moisture and their influence on the transport mechanism. All governing differential equations are solved with appropriate boundary conditions to obtain concentration and stress profiles. It is concluded that non- Fickian and anomalous transport of moisture in epoxy composites can occur under certain conditions, leading to stress accumulation close to the fibers of the composite.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The Design and Analysis of Experiments

Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

Harrison's Principles of Internal Medicine

Abstract: The 11th edition of Harrison's Principles of Internal Medicine welcomes Anthony Fauci to its editorial staff, in addition to more than 85 new contributors. While the organization of the book is similar to previous editions, major emphasis has been placed on disorders that affect multiple organ systems. Important advances in genetics, immunology, and oncology are emphasized. Many chapters of the book have been rewritten and describe major advances in internal medicine. Subjects that received only a paragraph or two of attention in previous editions are now covered in entire chapters. Among the chapters that have been extensively revised are the chapters on infections in the compromised host, on skin rashes in infections, on many of the viral infections, including cytomegalovirus and Epstein-Barr virus, on sexually transmitted diseases, on diabetes mellitus, on disorders of bone and mineral metabolism, and on lymphadenopathy and splenomegaly. The major revisions in these chapters and many

Understanding biophysicochemical interactions at the nano–bio interface

Abstract: Rapid growth in nanotechnology is increasing the likelihood of engineered nanomaterials coming into contact with humans and the environment. Nanoparticles interacting with proteins, membranes, cells, DNA and organelles establish a series of nanoparticle/biological interfaces that depend on colloidal forces as well as dynamic biophysicochemical interactions. These interactions lead to the formation of protein coronas, particle wrapping, intracellular uptake and biocatalytic processes that could have biocompatible or bioadverse outcomes. For their part, the biomolecules may induce phase transformations, free energy releases, restructuring and dissolution at the nanomaterial surface. Probing these various interfaces allows the development of predictive relationships between structure and activity that are determined by nanomaterial properties such as size, shape, surface chemistry, roughness and surface coatings. This knowledge is important from the perspective of safe use of nanomaterials.