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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Assessment of the degree of hydration of ocular surface tissues using THz reflectometry

Using the effective medium model, the complex permittivity of the ocular surface system in the THz frequency range is considered. The penetration depth of THz radiation and the sensitivity of the reflected component to the dynamics of evaporation of the tear film are discussed. The results of in vivo experiments aimed to determine the reflection coefficient of the ocular surface using continuous THz reflectometers are well described using the developed model. (paper)

36 MATERIALS SCIENCE↗
NASA NTRS2002

Formation of three-dimensional cell/polymer constructs for bone tissue engineering in a spinner flask and a rotating wall vessel bioreactor

The aim of this study is to investigate the effect of the cell culture conditions of three-dimensional polymer scaffolds seeded with rat marrow stromal cells (MSCs) cultured in different bioreactors concerning the ability of these cells to proliferate, differentiate towards the osteoblastic lineage, and generate mineralized extracellular matrix. MSCs harvested from male Sprague-Dawley rats were culture expanded, seeded on three-dimensional porous 75:25 poly(D,L-lactic-co-glycolic acid) biodegradable scaffolds, and cultured for 21 days under static conditions or in two model bioreactors (a spinner flask and a rotating wall vessel) that enhance mixing of the media and provide better nutrient transport to the seeded cells. The spinner flask culture demonstrated a 60% enhanced proliferation at the end of the first week when compared to static culture. On day 14, all cell/polymer constructs exhibited their maximum alkaline phosphatase activity (AP). Cell/polymer constructs cultured in the spinner flask had 2.4 times higher AP activity than constructs cultured under static conditions on day 14. The total osteocalcin (OC) secretion in the spinner flask culture was 3.5 times higher than the static culture, with a peak OC secretion occurring on day 18. No considerable AP activity and OC secretion were detected in the rotating wall vessel culture throughout the 21-day culture period. The spinner flask culture had the highest calcium content at day 14. On day 21, the calcium deposition in the spinner flask culture was 6.6 times higher than the static cultured constructs and over 30 times higher than the rotating wall vessel culture. Histological sections showed concentration of cells and mineralization at the exterior of the foams at day 21. This phenomenon may arise from the potential existence of nutrient concentration gradients at the interior of the scaffolds. The better mixing provided in the spinner flask, external to the outer surface of the scaffolds, may explain the accelerated proliferation and differentiation of marrow stromal osteoblasts, and the localization of the enhanced mineralization on the external surface of the scaffolds. Copyright 2002 Wiley Periodicals, Inc.

NASA Discipline Cell Biology↗
NASA NTRS1992

Purification and sequence analysis of two rat tissue inhibitors of metalloproteinases

Two protein inhibitors of metalloproteinases (TIMP) were isolated from medium conditioned by the clonal rat osteosarcoma line UMR 106-01. Initial purification of both a 30-kDa inhibitor and a 20-kDa inhibitor was accomplished using heparin-Sepharose chromatography with dextran sulfate elution followed by DEAE-Sepharose and CM-Sepharose chromatography. Purification of the 20-kDa inhibitor to homogeneity was completed with reverse-phase high-performance liquid chromatography. The 20-kDa inhibitor was identified as rat TIMP-2. The 30-kDa inhibitor, although not purified to homogeneity, was identified as rat TIMP-1. Amino terminal amino acid sequence analysis of the 30-kDa inhibitor demonstrated 86% identity to human TIMP-1 for the first 22 amino acids while the sequence of the 20-kDa inhibitor was identical to that of human TIMP-2 for the first 22 residues. Treatment with peptide:N-glycosidase F indicated that the 30-kDa rat inhibitor is glycosylated while the 20-kDa inhibitor is apparently unglycosylated. Inhibition of both rat and human interstitial collagenase by rat TIMP-2 was stoichiometric, with a 1:1 molar ratio required for complete inhibition. Exposure of UMR 106-01 cells to 10(-7) M parathyroid hormone resulted in approximately a 40% increase in total inhibitor production over basal levels.

NASA Discipline Musculoskeletal↗
DOE OSTI2025

Feedstock Variability: Differences Among Biomass Anatomical Fractions and Tissues

Corn stover is a versatile feedstock for producing biofuels and other sustainable products. However, its diverse chemical and physical attributes can hinder the processes that convert it into these compounds. The composition of corn stover varies according to factors including corn plant variety, cultivation conditions and maturity at harvest. In essence, corn stover consists of the polymers cellulose, hemicellulose and lignin. The structural core of plant cell walls consists of elongated chains of glucose molecules arranged in bundles of cellulose. Additionally, lower concentrations of hemicellulose, a complex carbohydrate composed of various sugars, form part of the matrix surrounding cellulose bundles. Lignin is a complex aromatic polymer that reinforces plant cell walls. Corn stover generally comprises 40%-50% cellulose, 20%-30% hemicellulose, and 20%-30% lignin. The ratios of these components vary based on the specific type of corn plant and the growth conditions. For example, corn plants cultivated in drought conditions exhibit higher lignin levels than those grown under optimal conditions. The compositional diversity resulting from growth conditions is most pronounced among the different anatomical fractions of the corn plant. Understanding and accommodating the variation among the anatomical fractions of corn stover can enhance the effective utilization of this resource.

09 BIOMASS FUELS↗
DOE OSTI2022

Seasonal non-structural carbohydrate dynamics differ between twig bark and xylem tissues

Despite extensive research non-structural carbohydrate (NSC), the distribution of total NSC (TNC) and its primary components (sugar and starch) to the bark and xylem of twigs remains poorly understood. We determined seasonal NSC dynamics in twig bark and xylem in seven temperate tree species exhibiting different xylem anatomies and leaf habits. Seasonal trends in sugar were similar across species with concentrations peaking at least 15 days earlier in the spring for xylem than bark. Furthermore, evergreens exhibited maximum bark starch concentrations in early spring, followed by declines throughout the growing season, whereas deciduous species exhibited early spring declines in bark starch, followed by late growing season increases. Evergreens exhibited limited seasonal variation in xylem starch concentrations, whereas deciduous species exhibited variation in xylem starch concentrations that was similar to variation in bark starch. With a few exceptions, concentrations and seasonal amplitudes for sugar, starch, and TNC were generally higher in bark than xylem. Sugar concentrations were generally higher than starch, especially in the bark, which resulted in variability of TNC concentrations in bark or xylem. NSC concentrations varied significantly between xylem and the entire twig when bark was not explicitly considered. Averaged across species, sugar, starch, and TNC content in bark accounted for 66%, 54%, and 61% of total twig content, respectively, even though bark only accounted for 53% of the total twig mass. We recommend quantifying bark sugar and starch separately from xylem when determining twig NSC concentration and content.

59 BASIC BIOLOGICAL SCIENCES↗