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Search Publications by: Joy Dunkers (Fed)

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Displaying 1 - 25 of 98

Three-dimensional, label-free cell viability measurements in tissue engineering scaffolds using optical coherence tomography

March 14, 2023
Author(s)
Greta Babakhanova, Anant Agrawal, Deepika Arora, Allison Horenberg, Jagat Budhathoki, Joy Dunkers, Joe Chalfoun, Peter Bajcsy, Carl Simon Jr.
In the field of tissue engineering, 3D scaffolds and cells are often combined to yield constructs that are used as therapeutics to repair or restore tissue function in patients. Viable cells are required to achieve the intended mechanism of action for the

Report from the NIST Workshop: Launch of the Rapid Microbial Testing Methods Consortium

September 27, 2022
Author(s)
Nancy Lin, Scott Jackson, Stephanie Servetas, Kirsten Parratt, Joy Dunkers, Tara Eskandari, Sheng Lin-Gibson
On September 17, 2020, NIST hosted a virtual workshop to launch the Rapid Microbial Testing Methods (RMTM) Consortium. The RMTM Consortium aims to address the need for measurements and standards to increase confidence in the use of rapid testing for

Micromechanical Compatibility Between Cells and Scaffolds Directs Phenotypic Transition of Stem Cells

January 28, 2022
Author(s)
Yang Song, Jiaoyue Long, Jeremiah Woodcock, Joy Dunkers, Hung Chun Lin, Douglas M. Fox, Xiaoling Liao, Yonggang Lv, Li Yang, Martin Chiang
This study experimentally substantiates the micromechanical compatibility between cell and substrate is essential for cells to achieve energetically favorable mechanotransduction that directs phenotypic transitions. The argument for this compatibility is

Towards Absolute Viability Measurements for Bacteria

September 12, 2021
Author(s)
Joy Dunkers, Hariharan K. Iyer, Brynna H. Jones, Charles Camp, Stephan J. Stranick, Nancy Lin
Quantifying viable, vegetative bacteria is a critical measurand in healthcare diagnostics, food safety, and antimicrobial development. Viability determination has traditionally relied on such techniques as plate counting, colorimetric or fluorescent

Methods for Characterization of Bioactivity Using Confocal Microscopy

December 1, 2020
Author(s)
Jirun Sun, Nancy Lin, Joy Dunkers, Sheng Lin-Gibson
One common tissue engineering approach for regenerating or replacing damaged tissues involves a porous polymeric scaffold. The scaffolds serve as the mechanical framework for cell attachment and growth, and generate an environment with features that span

Key Considerations for Microbial Viability Measurements

January 14, 2020
Author(s)
Joy Dunkers, Sandra M. Da Silva, Stephanie Servetas, James J. Filliben, Guilherme L. Pinheiro, Nancy Lin
Making reliable measurements of antimicrobial killing efficacy requires careful consideration of the sources of biological variability, measurement bias and error throughout the entire workflow. For ultraviolet-C (UV-C) disinfection, killing efficacy is

Structural Insights into DNA-Stabilized Silver Clusters

May 10, 2019
Author(s)
Danielle Schultz, Robert G. Brinson, Fahriye N. Sari, Jeffrey Fagan, Christina Bergonzo, Nancy Lin, Joy Dunkers
The structure and dynamics of Ag complexes derived from single stranded DNA (ssDNA) is less understood than their double stranded (dsDNA) counterparts despite their great promise as fluorescent biological probes and sensors. In this work, we seek new

Roles of Nanofiber Scaffold Structure and Chemistry in Directing Human Bone Marrow Stromal Cell Response

August 22, 2016
Author(s)
Sumona Sarkar, Bryan A. Baker, Desu Chen, Patrick S. Pine, Jennifer H. McDaniel, Marc L. Salit, Wolfgang Losert, Carl G. Simon Jr., Joy P. Dunkers
Nanofiber technology has emerged as a promising tool to recapitulate the native extracellular matrix structure; however the properties of nanofibers governing cell-material interactions are still largely undetermined. In this study we have systematically

Machine Learning Strategy to Determine Cell Shape Phenotypes Associated with Micro-Environmental Cues

June 25, 2016
Author(s)
Desu Chen, Sumona Sarkar, Julian Candia, Carl G. Simon Jr., Wolfgang Losert, Joy P. Dunkers, Stephen J. Florczyk, Subhadip Bodhak, Meghan Driscoll
Cell morphology has been identified as a potential indicator of stem cell response and function in biomaterial environments. However, determination of cell shape phenotype in biomaterials is complicated by heterogeneous cell populations, heterogeneous

The Testing Program at NIST on Fibers Used in Soft Body Armor Applications

March 21, 2015
Author(s)
Walter G. McDonough, Amanda L. Forster, Jae Hyun Kim, Nathanael A. Heckert, Joy P. Dunkers, Scott A. Wight, Gale A. Holmes
The goal of this paper and presentation is to give an update of the research effort to date being conducted at the National Institute of Standards and Technology (NIST) on polymeric fibers used in soft body armor with a special emphasis on new fibers under

TESTING AND ANALYSES OF COPOLYMER FIBERS BASED ON 5-AMINO-2-(P-AMINOPHENYL)-BENZIMIDAZOLE

September 22, 2014
Author(s)
Walter G. McDonough, Joy P. Dunkers, Amanda L. Forster, Jae Hyun Kim, Scott A. Wight, Gale A. Holmes
Since the well-publicized failure of a body armor used by a police officer at a threat level the armor had been designed to survive, it has become imperative that the long-term properties and performance of new fibers being considered for use be understood

Machine Learning Analysis for Identification of Cell Shape Metrics Associated with Stem Cell Differentiation in Nanofiber Scaffolds

April 19, 2014
Author(s)
Desu Chen, Sumona Sarkar, Stephen J. Florczyk, Subhadip Bodhak, Carl G. Simon Jr., Joy P. Dunkers, Julian Candia, Wolfgang Losert
Cell shape has been demonstrated to be closely related to cell function and may be an important predictor of cell fate. Many metrics are available to describe cell shape, however the relationship of these metrics to cell fate are not well understood

R Implementation of a Polyhedral Approximation to a 3D Set of Points Using the Alpha-Shape

January 1, 2014
Author(s)
Thomas V. Lafarge, Beatriz Pateiro Lopez, Antonio M. Possolo, Joy P. Dunkers
This work describes the implementation in R of the alpha-shape of a finite set of points in three-dimensional space. This geometric construct generalizes the convex hull and estimates the shape of non-convex and even non-connected sets in 3D, given random

Analyzing a Co-Polymer Aramid Fiber for Use in Soft Body Armor

October 25, 2013
Author(s)
Walter G. McDonough, Jae Hyun Kim, Nathanael A. Heckert, Amanda L. Forster, Scott A. Wight, Joy P. Dunkers, Gale A. Holmes
Since the well-publicized failure of body armor used by a police officer, it has become imperative that the long-term properties and performance of new fibers being considered for use be understood. The range of interest is from the molecular properties of

Effect of Surface Chemistry on Stem Cell Response in 2-D vs. 3-D Cell Culture Niches

April 19, 2013
Author(s)
Sumona Sarkar, Carl G. Simon Jr., Roberta I. Lock, Joy P. Dunkers
To develop tissue engineered devices for regenerative medicine strategies, key scaffold properties for directing stem cell response must be identified. As focus shifts from 2-D to 3-D culture systems in an attempt to better recapitulate the natural

Three-dimensional Shape Metrology for Tissue Engineering

April 21, 2012
Author(s)
Joy P. Dunkers, Antonio M. Possolo, Thomas V. Lafarge, Beatriz Pateiro-Lopez, Jeffrey Coles, Carl G. Simon Jr.
The physical and chemical properties of a tissue scaffold influences cell response and therefore the success of the resulting tissue construct. Scaffold structure from nanometers to millimeters can direct cell behavior, from viability to proliferation to

OVERVIEW OF THE TESTING PROGRAM ON FIBERS USED IN BALLISTIC APPLICATIONS

April 4, 2012
Author(s)
Amanda L. Forster, Haruki Kobayashi, Jae H. Kim, Michael A. Riley, Joy Dunkers, Scott Wight, Kirk D. Rice, Gale A. Holmes
The goal of this paper and presentation is to give an overview of the research effort to date being conducted at the National Institute of Standards and Technology on polymeric fibers used in soft body armor (SBA) and a discussion of future directions. The

The Effects of Folding on High Strength Fibers Used in Soft Body Armor

January 23, 2012
Author(s)
Haruki Kobayashi, Walter G. McDonough, Joy Dunkers, Jae H. Kim, Hae-Jeong Lee, Scott Wight, Amanda L. Forster, Kirk D. Rice, Gale A. Holmes
Poly (p-phenylene benzobisoxazole) (PBO) fibers have been used in soft body armor (SBA) because of their high mechanical strength. However, there was an unexpected failure of a first responder's SBA which was composed of PBO fiber that was in service for

How well do you know your MATES???

December 1, 2011
Author(s)
Joy P. Dunkers
There is a group that quietly goes about the business of advancing the areas of tissue engineering and regenerative medicine. I say quietly because their work, while impactful, is not well known outside of government circles. How well do you know your

Analyses of a Cantilever-Beam Based Instrument for Evaluating the Development of Polymerization Stresses

August 9, 2011
Author(s)
Martin Y. Chiang, Anthony A. Giuseppetti, Joy P. Dunkers, Jing Qian, Sheng Lin-Gibson, Gary E. Schumacher, Joseph M. Antonucci
Analytical and finite element analyses have been performed on a cantilever-beam based methodology (tensometer) for evaluating the development of stresses as the concomitant of constrained polymerization shrinkage. A guideline for designing a tensometer