A 2-D Model of Flow-Induced Alterations in the Geometry, Structure, and Properties of Carotid Arteries

2004 ◽  
Vol 126 (3) ◽  
pp. 371-381 ◽  
Author(s):  
R. L. Gleason ◽  
L. A. Taber ◽  
J. D. Humphrey
Keyword(s):  
Arterial Wall ◽  
Carotid Arteries ◽  
Constitutive Relations ◽  
Structure And Properties ◽  
First Order ◽  
First Order Kinetics ◽  
Comprehensive Theory ◽  
Constrained Mixture ◽  
Distribution Of Stress ◽  
D Model

Evidence from diverse investigations suggests that arterial growth and remodeling correlates well with changes in mechanical stresses from their homeostatic values. Ultimately, therefore, there is a need for a comprehensive theory that accounts for changes in the 3-D distribution of stress within the arterial wall, including residual stress, and its relation to the mechanisms of mechanotransduction. Here, however, we consider a simpler theory that allows competing hypotheses to be tested easily, that can provide guidance in the development of a 3-D theory, and that may be useful in modeling solid-fluid interactions and interpreting clinical data. Specifically, we present a 2-D constrained mixture model for the adaptation of a cylindrical artery in response to a sustained alteration in flow. Using a rule-of-mixtures model for the stress response and first order kinetics for the production and removal of the three primary load-bearing constituents within the wall, we illustrate capabilities of the model by comparing responses given complete versus negligible turnover of elastin. Findings suggest that biological constraints may result in sub-optimal adaptations, consistent with reported observations. To build upon this finding, however, there is a need for significantly more data to guide the hypothesis testing as well as the formulation of specific constitutive relations within the model.

Salicylate Kinetics In The Rat: Relationship To Antithrombotic Activity

1981 ◽  
Author(s):  
R B Philp ◽  
I Francey
Keyword(s):  
Carotid Arteries ◽  
Post Injection ◽  
Antithrombotic Effect ◽  
Protective Level ◽  
Antithrombotic Activity ◽  
First Order ◽  
First Order Kinetics ◽  
Salicylate Level ◽  
Before And After ◽  
Prostacyclin Synthesis

Recently we reported that acetylsalicylic acid (ASA) 100 mg/kg i.v. had no antithrombotic effect in a rat model of arterial thrombosis whereas 200 mg/kg i.v. had significant antithrombotic activity. The present study investigates salicylate kinetics at the non-protective level. Carotid arteries of urethane-anesthetized rats were injured electrically (1 mA, DC, for 1 min) and thrombogenesis measured by recording downstream temperature. Right and left side injuries were compared before and after ASA, 100 mg/kg i.v. Blood samples were collected at various times post injection and serum assayed for salicylate content by Trinder’s method. All salicylate levels are reported as mg/dL ± SEM. Control injuries produced a temperature fall of 1.4°C ± 0.08 (SEM) and post ASA injuries a fall of 1.8°C ± 0.17 (SEM) (P < .1 > .05). Serum salicylate was 20 mg ± 4.58 1 min post injection and the calculated lh was 40 min with decay following first order kinetics. The intraperitoneal injection of ASA 200 mg/kg produced a serum salicylate level of 8.1 ± 1.55 5 min post injection with a peak of 19 ± 2.03 30 min post injection. Both absorption and elimination followed first order kinetics with Th values of 10 and 44 min respectively. Urine collected 40 min post injection contained 9.4 ± 3.38 free salicylate which increased to about 40 following chemical digestion, indicating the presence of metabolites. The results indicate that serum salicylate levels < 20 do not offer antithrombotic protection in this model and that this level is achieved only briefly following ASA 100 mg/kg i.v. or 200 mg/kg i.p. The brief half-life of ASA in the rat has implications for the interpretation of data concerning the inhibition of prostacyclin synthesis by vessel wall. The wide variation in effective ASA doses reported for various animal models of thrombosis is probably a function of the nature of the model rather than of efficient prostacyclin synthesis.

Constrained Mixture Models of Arterial Homeostasis and Adaptation

2009 ◽  
Author(s):  
J. D. Humphrey
Keyword(s):  
Residual Stresses ◽  
Arterial Wall ◽  
Constitutive Relations ◽  
Material Behavior ◽  
Biological Information ◽  
Matrix Remodeling ◽  
Constrained Mixture ◽  
Classical Models ◽  
Mechanical Homeostasis ◽  
Altered Blood

Phenomenological models of the mechanical behavior of the arterial wall continue to play important roles in vascular mechanics. Indeed, such models revealed the importance of residual stresses in homogenizing the transmural distribution of stress in normalcy [1], which in turn led to one of the most important hypotheses in vascular mechanobiology — the existence of a mechanical homeostasis [2]. Nevertheless, classical models are not able to exploit the growing information on the different mechanical properties and rates and extents of turnover of different structurally significant constituents within the arterial wall. To address this need, we have proposed a structurally-motivated, materially nonuniform model of the arterial wall based on a theory of constrained mixtures [cf. 3]. Key features of this model include the ability to prescribe individual stored energy functions for different structurally significant constituents that are constrained to move together within the overall wall while being allowed to possess individual evolving natural (stress-free) configurations, and the ability to prescribe separate stress-mediated constitutive relations for constituent production and removal. We have shown that this constrained mixture approach can capture many salient features of arterial adaptations (e.g., evolving changes in geometry, overall material behavior, and collagen to elastin ratios) to both altered mechanical loading (e.g., altered blood flow and pressure as well as axial stretch) and disease progression (e.g., enlargement of intracranial aneurysms and the development and resolution of cerebral vasospasm). We submit that, in contrast to models built on the assumption of kinematic growth, this constrained mixture approach can incorporate increasingly detailed biological information on cell and matrix turnover and can thereby begin to generate and test novel hypotheses on mechanisms of arterial homeostasis and adaptation. We will show, for example, that the constrained mixture model suggests a possible mechanism for the origin of residual stresses and axial prestretches, the importance of cellular deposition of new extracellular matrix proteins within stressed states, the complementary roles of vasoactivity and matrix remodeling, and stress mediation of matrix turnover [4,5]. We note, in particular, the importance of residual stress and axial prestress in establishing arterial homeostasis and thus targets for subsequent adaptations [5,6].

Photo-catalytic degradation of gaseous pollutants in paper mills of southern China

TAPPI Journal ◽  
2018 ◽  
Vol 17 (03) ◽  
pp. 167-178 ◽  
Author(s):  
Xin Tong ◽  
Jiao Li ◽  
Jun Ma ◽  
Xiaoquan Chen ◽  
Wenhao Shen
Keyword(s):  
Degradation Rate ◽  
Southern China ◽  
Catalytic Degradation ◽  
Pulp And Paper ◽  
Gaseous Pollutants ◽  
Pulp And Paper Mills ◽  
Paper Mills ◽  
Initial Concentration ◽  
First Order ◽  
First Order Kinetics

Studies were undertaken to evaluate gaseous pollutants in workplace air within pulp and paper mills and to consider the effectiveness of photo-catalytic treatment of this air. Ambient air at 30 sampling sites in five pulp and paper mills of southern China were sampled and analyzed. The results revealed that formaldehyde and various benzene-based molecules were the main gaseous pollutants at these five mills. A photo-catalytic reactor system with titanium dioxide (TiO2) was developed and evaluated for degradation of formaldehyde, benzene and their mixtures. The experimental results demonstrated that both formaldehyde and benzene in their pure forms could be completely photo-catalytic degraded, though the degradation of benzene was much more difficult than that for formaldehyde. Study of the photo-catalytic degradation kinetics revealed that the degradation rate of formaldehyde increased with initial concentration fitting a first-order kinetics reaction. In contrast, the degradation rate of benzene had no relationship with initial concentration and degradation did not conform to first-order kinetics. The photo-catalytic degradation of formaldehyde-benzene mixtures indicated that formaldehyde behaved differently than when treated in its pure form. The degradation time was two times longer and the kinetics did not reflect a first-order reaction. The degradation of benzene was similar in both pure form and when mixed with formaldehyde.

Kinetic of oxidation of methyl orange by vanadium(V) under conditions VO2+ and decavanadates coexist: Catalysis by Triton X-100 micellar medium

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Methyl Orange ◽  
Solution Ph ◽  
Vanadium Concentration ◽  
Limiting Behavior ◽  
First Order ◽  
First Order Kinetics ◽  
Ph Range ◽  
Kinetic Pattern ◽  
Triton X ◽  
Kinetics Of

The kinetics of oxidation of methyl orange by vanadium(V) {V(V)} has been investigated in the pH range 2.3-3.79. In this pH range V(V) exists both in the form of decavanadates and VO2+. The kinetic results are distinctly different from the results obtained for the same reaction in highly acidic solution (pH &lt; 1) where V(V) exists only in the form of VO2+. The reaction obeys first order kinetics with respect to methyl orange but the rate has very little dependence on total vanadium concentration. The reaction is accelerated by H+ ion but the dependence of rate on [H+] is less than that corresponding to first order dependence. The equilibrium between decavanadates and VO2+ explains the different kinetic pattern observed in this pH range. The reaction is markedly accelerated by Triton X-100 micelles. The rate-[surfactant] profile shows a limiting behavior indicative of a unimolecular pathway in the micellar pseudophase.

Biodegradation rates of aromatic contaminants in biofilm reactors

1995 ◽  
Vol 31 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Jean-Pierre Arcangeli ◽  
Erik Arvin
Keyword(s):  
Aromatic Hydrocarbons ◽  
Competitive Inhibition ◽  
Removal Rate ◽  
First Order ◽  
Biofilm Reactors ◽  
First Order Kinetics ◽  
Reducing Conditions ◽  
Low Concentrations ◽  
Degradation Rates ◽  
Order Surface

This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/l concentration range. The biodegradation rates of the following compounds were investigated in biofilm systems: aromatic hydrocarbons, phenol, methylphenols, chlorophenols, nitrophenol, chlorobenzenes and aromatic nitrogen-, sulphur- or oxygen-containing heterocyclic compounds (NSO-compounds). Furthermore, a comparison with degradation rates observed for easily degradable organics is also presented. At concentrations below 20-100 μg/l the degradation of the aromatic compounds was typically controlled by first order kinetics. The first-order surface removal rate constants were surprisingly similar, ranging from 2 to 4 m/d. It appears that NSO-compounds inhibit the degradation of aromatic hydrocarbons, even at very low concentrations of NSO-compounds. Under nitrate-reducing conditions, toluene was easily biodegraded. The xylenes and ethylbenzene were degraded cometabolically if toluene was used as a primary carbon source; their removal was influenced by competitive inhibition with toluene. These interaction phenomena are discussed in this paper and a kinetic model taking into account cometabolism and competitive inhibition is proposed.

In-vitro Kinetic Hydrolysis Study of Metronidazole Derivatives with Carvacrol and Eugenol Using Validated RP-HPLC Method

2020 ◽  
Vol 16 ◽  
Author(s):  
M. Alarjah
Keyword(s):  
Half Life ◽  
Hplc Method ◽  
Hydrolysis Rate ◽  
First Order ◽  
First Order Kinetics ◽  
Rp Hplc ◽  
Pharmacokinetic Properties ◽  
Pseudo First Order ◽  
Kinetic Hydrolysis

Background: Prodrugs principle is widely used to improve the pharmacological and pharmacokinetic properties of some active drugs. Much effort was made to develop metronidazole prodrugs to enhance antibacterial activity and or to improve pharmacokinetic properties of the molecule or to lower the adverse effects of metronidazole. Objective: In this work, the pharmacokinetic properties of some of monoterpenes and eugenol pro metronidazole molecules that were developed earlier were evaluated in-vitro. The kinetic hydrolysis rate constants and half-life time estimation of the new metronidazole derivatives were calculated using the validated RP-HPLC method. Method: Chromatographic analysis was done using Zorbbax Eclipse eXtra Dense Bonding (XDB)-C18 column of dimensions (250 mm, 4.6 mm, 5 μm), at ambient column temperature. The mobile phase was a mixture of sodium dihydrogen phosphate buffer of pH 4.5 and methanol in gradient elution, at 1ml/min flow rate. The method was fully validated according to the International Council for Harmonization (ICH) guidelines. The hydrolysis process carried out in an acidic buffer pH 1.2 and in an alkaline buffer pH 7.4 in a thermostatic bath at 37ºC. Results: The results followed pseudo-first-order kinetics. All metronidazole prodrugs were stable in the acidic pH, while they were hydrolysed in the alkaline buffer within a few hours (6-8 hr). The rate constant and half-life values were calculated, and their values were found to be 0.082- 0.117 hr-1 and 5.9- 8.5 hr., respectively. Conclusion: The developed method was accurate, sensitive, and selective for the prodrugs. For most of the prodrugs, the hydrolysis followed pseudo-first-order kinetics; the method might be utilised to conduct an in-vivo study for the metronidazole derivatives with monoterpenes and eugenol.

Decomposition of 4,4'-(Diazoamino)-bis(5-methoxy-2-methylbenezenesulfonic Acid) in Solutions ofFD&C Red No. 40

1984 ◽  
Vol 67 (4) ◽  
pp. 844-845
Author(s):  
Naomi Richfield-Fratz
Keyword(s):  
Liquid Chromatography ◽  
Aqueous Solutions ◽  
Borate Buffer ◽  
Sodium Borate ◽  
First Order ◽  
First Order Kinetics ◽  
Color Additive ◽  
Sodium Borate Buffer

Abstract 4,4'-(Diazoamino)-bis(5-methoxy-2-methylbenzenesuIfonic acid), when present as a reaction by-product in FD&C Red No. 40, is shown to decompose rapidly in aqueous solutions of the color additive. The decomposition is halted by the addition of sodium borate buffer. Quantitationly liquid chromatography shows that decomposition is nonlinear with time and follows approximate first order kinetics.

Validity of ultrasound arterial wall vascularization for assessment of vascular inflammation

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
W Sato ◽  
Y Kobayashi ◽  
M Otaka ◽  
M Unuma ◽  
T Yamanaka ◽  
...  
Keyword(s):  
Carotid Stenosis ◽  
Predictive Value ◽  
Arterial Wall ◽  
Carotid Arteries ◽  
Vascular Inflammation ◽  
False Negative ◽  
Intraplaque Hemorrhage ◽  
Funding Source ◽  
Negative Finding ◽  
18F Fdg

Abstract Background Vascular inflammation plays a fundamental role in most vascular diseases including atherosclerosis and vasculitis syndrome, in which arterial wall vascularization (AWV) frequently develops. Visualization of AWV is informative in detecting the vascular inflammation but is challenging. A new ultrasound technique (superb micro-vascular imaging [SMI]) allows the detection of extremely low-velocity flows. We examined an availability of SMI for assessment of the instability of atherosclerotic plaques and the activity of Takayasu arteritis (TA). Methods and results The study consists of two independent and consecutive parts A and B, examined in carotid stenosis (A) and TA (B), respectively. In part A, 12 patients with symptomatic severe carotid stenosis (CS group) scheduled for carotid endarterectomy were enrolled. In six of 12 patients, preoperative ultrasonography with SMI showed intraplaque neovascularization at the plaque shoulder. Postoperatively, histopathology confirmed the neovessels at the corresponding sites of visualized AWV. SMI had a sensitivity of 67%, specificity of 90% for detection of AWV in CS group. In SMI analysis, false positive findings were caused by motion artifact and arterial wall calcification, and a false negative finding is attributed by intraplaque hemorrhage. In part B, 10 patients with TA were enrolled. All patients underwent 18F-FDG-PET/CT, and its vascular uptake were compared with AWV detected by SMI. Bilateral common carotid arteries (CCA), internal carotid arteries and common iliac arteries were examined by SMI. Active vascular 18F-FDG uptake (max SUV &gt;2.1) were found at five sites in three patients, which were not significantly correlated with the prevalence of macaroni sign, increase in C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Of note, SMI revealed AWV at five sites corresponding to uptake of 18F-FDG, with a sensitivity/specificity of 100% and 98%, positive predictive value 71%, and a negative predictive value 100%. Conclusion SMI enables visualization of AWV at vulnerable plaque in CS patients and at 18F-FDG positive sites in TA patients. SMI has potential as a modality to detect the vascular inflammation. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Grant-in-Aid for Scientific Research, Japan

scholarly journals Comparative Study of Chemical Stability of Two H1Antihistaminic Drugs, Terfenadine and ItsIn VivoMetabolite Fexofenadine, Using LC-UV Methods

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Anna Gumieniczek ◽  
Anna Berecka-Rycerz ◽  
Rafał Pietraś ◽  
Izabela Kozak ◽  
Karolina Lejwoda ◽  
...  
Keyword(s):  
Comparative Study ◽  
Chemical Stability ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of Degradation ◽  
Effects Of Temperature ◽  
High Doses ◽  
Antihistaminic Drugs ◽  
Kinetics Of

A comparative study of chemical stability of terfenadine (TER) and itsin vivometabolite fexofenadine (FEX) was performed. Both TER and FEX were subjected to high temperature at different pH and UV/VIS light at different pH and then quantitatively analyzed using new validated LC-UV methods. These methods were used to monitor the degradation processes and to determine the kinetics of degradation for both the compounds. As far as the effects of temperature and pH were concerned, FEX occurred more sensitive to degradation than TER. As far as the effects of UV/VIS light and pH were concerned, the both drugs were similarly sensitive to high doses of light. Using all stress conditions, the processes of degradation of TER and FEX followed the first-order kinetics. The results obtained for these two antihistaminic drugs could be helpful in developing their new derivatives with higher activity and stability at the same time.

The conversion of ethylene to ethylidyne on Pt(111): non-first order kinetics and ensemble effects

1994 ◽  
Vol 301 (1-3) ◽  
pp. 177-196 ◽  
Author(s):  
W. Erley ◽  
Y. Li ◽  
D.P. Land ◽  
John C. Hemminger
Keyword(s):  
First Order ◽  
First Order Kinetics ◽  
Ensemble Effects
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