Nonlinear regression least‐squares method for determining relaxation time spectra for processes with first‐order kinetics

1983 ◽  
Vol 54 (5) ◽  
pp. 2137-2146 ◽  
Author(s):  
J. R. Cost
Keyword(s):  
Relaxation Time ◽  
Least Squares ◽  
Nonlinear Regression ◽  
Least Squares Method ◽  
First Order ◽  
First Order Kinetics

Characterization of a Fibrin Glue-Gdnf Slow-Release Preparation

1998 ◽  
Vol 7 (1) ◽  
pp. 53-61
Author(s):  
Henrich Cheng ◽  
Matt Fraidakis ◽  
Birger Blombäck ◽  
Paul Lapchak ◽  
Barry Hoffer ◽  
...  
Keyword(s):  
Linear Regression ◽  
Least Squares ◽  
Fibrin Glue ◽  
Trophic Factor ◽  
Adult Rats ◽  
First Order ◽  
First Order Kinetics ◽  
Implantation Sites ◽  
The Mean ◽  
Over Time

One novel method to deliver trophic factor locally in the CNS is to mix it into fibrin glue. In the present studies, [125I]-labeled GDNF-containing fibrin glue balls were used to determine binding and spread of the trophic factor. First, the binding of different concentrations of [125I]-labelèd GDNF in fibrin glue was determined in vitro. Within the six concentrations used (from 200 nM to 0.004 nM, 0 M as control), there was a strong linear correlation between the [125I]-GDNF concentration and the recovered radioactivity (r = 0.992). The mean bound radioactivity in 16 samples with 4 nM [125I]-GDNF was 71262 + 2710 CPM, and accounted for 89.8% of the mean initial count of free [125I]-GDNF (79369 + 3499 CPM). Second, [125I]-GDNF-containing glue balls were implanted into the anterior chamber of adult rats. The implanted fibrin glue balls decreased in size with time, but could still be identified on the irises 2 wk after implantation. Radioactivity was concentrated at the implantation sites in the early stages with a distribution in the surrounding iris tissue, which became separated into focal radioactive spots at the third week. Counts of radioactivity were significantly higher in the [125I]-GDNF glue ball-implanted irises than controls until 14 days after implantation. A study of the [125I] decay over time using least-squares linear regression demonstrated first-order kinetics (r = —0.98, p < 0.02) with k = 0.0091 and T 1/2 = 76 h. Finally, [125I]-GDNF–containing glue balls were implanted in the spinal cord of adult rats. Radioactivity was concentrated at the implantation sites in the early stages and was later distributed more widely in the surrounding thoracic cord. The [125I]-GDNF–containing glue degraded over time and became a porous meshwork with decreasing radioactivity at the later time points. Radioactivity in the spinal cords subjected to implantation of [125I]-GDNF–containing glue balls was higher than in controls for 14 days. Study of the [125I] decay by time with least-squares linear regression demonstrated first-order kinetics (r = -0.97, p = 0.001) with T 1/2 = 75.6 h. We conclude that the trophic factor GDNF becomes bound in the fibrin glue matrix from which it is gradually released. Our results suggest that fibrin glue is an effective substrate for keeping a trophic factor localized in situ for a finite period, protected from the circulation, surrounding aqueous humor or CSF.

scholarly journals The Effect of Tb and Sm Ions on the Photochromic Behavior of Two Spiropyrans of Benzoxazine Series in Solution

2008 ◽  
Vol 2008 ◽  
pp. 1-4 ◽  
Author(s):  
Esam Bakeir ◽  
G. M. Attia ◽  
Maria Lukyanova ◽  
Boris Lukyanov ◽  
M. S. A. Abdel-Mottaleb
Keyword(s):  
Relaxation Time ◽  
Ring Opening ◽  
Bond Cleavage ◽  
Lanthanide Ions ◽  
Photochromic Behavior ◽  
First Order ◽  
Color Development ◽  
First Order Kinetics ◽  
Thermal Bleaching ◽  
Color Enhancement

The photochromism of [7′-hydroxy-8′-formyl-3-methyl-4-oxospiro[1,3-benzoxazin-2,2′-[2H-1]benzopyran],SP(I),[7′-hydroxy-8′-formyl-3-benzyl-4-oxospiro[1,3-benzoxazin-2,2′-[2H-1]benzopyran] SP(II) and their coordination with Tb3+and Sm3+ ions have been studied in DMF. UV/vis induced-color development due to heterolytic bond cleavage of SP(I) and SP(II) is greatly influenced by complexation with the lanthanide ions. The irradiation-induced color enhancement due to ring opening and thermal decoloration of the open forms of SP(I), SP(II) follows first-order kinetics. Physical characteristics of the studied systems such as colorability and relaxation time of thermal bleaching parameters were determined. Moreover, light-energy transfer-induced luminescence of lanthanide ions via coordination with the two spirobenzoxazines was monitored.

A Fluidity-Based First-Order System Least-Squares Method for Ice Sheets

2017 ◽  
Vol 39 (2) ◽  
pp. B352-B374 ◽  
Author(s):  
Jeffery Allen ◽  
Chris Leibs ◽  
Tom Manteuffel ◽  
Harihar Rajaram
Keyword(s):  
Least Squares ◽  
Least Squares Method ◽  
Ice Sheets ◽  
Order System ◽  
First Order

A First-Order System Least Squares Method for Hyperelasticity

2014 ◽  
Vol 36 (5) ◽  
pp. B795-B816 ◽  
Author(s):  
Benjamin Müller ◽  
Gerhard Starke ◽  
Alexander Schwarz ◽  
Jörg Schröder
Keyword(s):  
Least Squares ◽  
Least Squares Method ◽  
Order System ◽  
First Order
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