Modeling and in vitro and in vivo characterization of a tissue engineered pancreatic substitute

In designing appropriate devices for the development of a functional pancreatic substitute, computational models capable of accurately predicting cellular behavior constitute a critical aspect. This study investigated the model-based design, fabrication and in vitro and in vivo experimental characterization of a pancreatic substitute consisting of mouse insulinoma cells encapsulated in agarose in a disk-shaped construct. Two construct prototypes were examined: (i) a single disk construct comprised of agarose and βTC3 cells; and (ii) a buffered disk construct, consisting of agarose and βTC3 cells, coated with an additional layer of pure agarose. Diffusional studies of glucose and insulin were performed to characterize the transport properties of the material. Three dimensional oxygen diffusion-reaction models were used to predict the appropriate cell loadings for the two construct prototypes under varying external oxygen tensions. In vitro and in vivo experiments found the overall viable cell number for each construct prototype plateaued to the same value, regardless of the initial cell seeding number, when constructs were placed under identical environmental conditions. Furthermore, mathematical model calculations correlated well with experimental in vitro and in vivo results of cell viability, indicating oxygen tension to be the dominating factor in establishing total viable cell number in these constructs. These results indicate that the development of a computational model capable of accurately predicting overall cell viability is useful for the development of tissue engineered constructs, when permissive matrices and continuous cell lines are used. The applicability of this modeling and experimental methodology in the development of agarose-based constructs for use as a bioartificial pancreas is discussed. The authors would like to dedicate this paper to the memory of the colleague, friend, and mentor Professor Ioannis (Yanni) Constantinidis, who died suddenly and untimely on April 16, 2006.     

自我的凝视:白居易的写真诗与对镜诗

文章探讨的是作者书写"看见自我"的视觉经验及其反思。在唐代诗人中,题咏自己的肖像画、书写揽镜自照心情者,以白居易(772～846)的作品最多,至少有十五首。文章即以白居易观看自己的肖像画以及照镜题材的诗作为例,分析诗人从凝视自我的视觉体验中感知的自我意识。诗人透过画像再现或镜面反射,得知三重层次的"自我形象"——真实自我的幻影、他人眼中的"我"以及理想之"我"的期许。     

Multiple Time Scales and the Lifetime Coefficient of Variation: Engineering Applications

We consider linear combinations of “natural” timescales and choose the “best” one which provides the minimum coefficient of variation of the lifetime. Our time scale is in fact a generalized Miner time scale because the latter is based on an appropriate weighting of the times spent on low and high level loadings. The suggested modus operandi for finding the“best” time scale has many features in common with the approach suggested by Farewell and Cox (1979) and Oakes (1995) which is devoted to multiple time scales in survival analysis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Bringing our bodies and ourselves back in: reflections on a past, present, and future "medical sociology"

This paper is a revision of an address given upon receipt of the Leo G. Reeder Award for Distinguished Scholarship in Medical Sociology. It was presented on August 14, 1990 to The Medical Sociology Section of the American Sociological Association during its annual meetings, held in Washington, DC. Herein I reflect on the structured silence of personal bodily experience and on the unfinished paradigmatic challenge of feminism as a way of leading to a new praxis in medical sociology.     

Informal caregivers' leisure time and stress

This article explores the disruption informal caregiving creates in the caregiver's family life and the relationship between leisure and stress caused by caregiving. The study finds that the caregiving setting, caregiver's sociodemographic characteristics, and economic variables (i.e., wage rate, nonwage income, and Medicaid coverage) significantly affect the caregiver's leisure. Additionally, reducing leisure leads to emotional and physical stress and less satisfaction with life overall. The article concludes with implications for public policy. Her research interests include long-term health care and medical service utilization for minority populations. She holds a doctorate from Northwestern University. He has published extensively in the areas of health services research and nonprofit organizations. His doctorate is from the University of Virginia.     

The psychiatric technician: trespasser or welcomed ally?

1. The increasing shortage of nurses, higher patient acuity levels, and greater demands placed on nursing to meet standards of care have contributed to the use of psychiatric technicians to alleviate the burden on nursing and ensure the delivery of quality patient care. 2. Psychiatric technicians provide care for a select group of patients under the supervision of the primary nurse. The patients assigned to psychiatric technicians require minimal direct nursing intervention. 3. Psychiatric technicians reported increased self-confidence and self-esteem; the nurses were able to perform more professional nursing activities, increasing their job satisfaction and promoting staff retention; and the patients received high-quality care.     

Software review: Bootstrapping and jacknifing with BOJA

Conclusion Apart from its use by statisticians and researchers, another major application of BOJA is in teaching statistics. It is easy to use and the onscreen display during a resampling analysis, together with the graphical display, makes it a useful teaching aid. This review was protracted because I wanted to keep playing with the package, especially by thinking up new ways to use it. I found it a thoroughly rewarding experience.     

Algebraic Methods for Polynomial Statistical Models

We describe applications of computational algebra to statistical problems of parameter identifiability, sufficiency, and estimation. The methods work for a family of statistical models that includes Poisson and binomial examples in network tomography.