69 research outputs found
Comparative Analysis of Geometric Models for Predicting the Dynamic Specific Surface of Foamlike Media
An adaptable geometric pore-scale model is proposed for predicting the specific surface area of actual foams. The proposed model, based on rectangular geometry, is compared to a cubic unit cell model from the literature based on cylindrical struts, a tetrakaidecahedron model as well as a dodecahedron model (both based on either cylindrical of triangular struts). The predicted specific surface areas of the proposed model are of the same order of magnitude as the other model predictions from the literature. The relative percentage errors in the predicted values are at most equal to the relative percentage errors associated with the measured diameter values. This is satisfactory, given the uncertainty in measuring the average pore-scale linear dimensions and also taking into consideration that the possibility of hollow struts, pore blockage and surface roughness are not accounted for in the model. The advantage of the proposed model is that only the solid width or the channel width needs to be known a priori to predict the specific surface area, and that it is physically adaptable
Understanding the relationship between high-density lipoprotein (HDL) subclass distribution and functionality in patients at risk of cardiovascular disease
Background: Risk factors for cardiovascular disease (CVD) include obesity, ethnicity and hypertension. High-density lipoprotein (HDL) has traditionally served as a marker for CVD risk. Latest studies, however, propose that the composition and subclass distribution and the anti-atherogenic function of HDL are more accurate predictors of CVD risk. We therefore explored whether obesity, ethnicity, exercise and hypertension may modulate HDL composition, subclass and function in three different sample populations of patients affected with these CVD risk factors. Methods: The first study sample population consisted of black and white obese and normal-weight South African women (n=40). In the second sample population, obese black South African women were randomly assigned to exercise (combined aerobic and resistance exercise 4 times/week) or control (sedentary) conditions for 12-weeks (n=32). The third sample population included Nigerian out-patients, divided into healthy controls, hypertensive patients and hypertensive patients with heart failure (HF) (n=80). HDL composition measurements included apolipoproteins A1 and M (ApoA1 and ApoM), paraoxonase (PON1) and platelet activating factor acetylhydrolase (PAF-AH) expression (using Western blotting) and sphingosine-1-phosphate (S1P) content (using mass spectometry). Levels of large, intermediate and small HDL subclasses were measured using the Lipoprint® system. HDL functionality was assessed by measuring PON1 activity, PAF-AH activity, reverse cholesterol efflux capacity, HDL-mediated activation of endothelial nitric oxide synthase (eNOS) and quantification of the expression of vascular cell adhesion molecule in endothelial cells. Results: In all sample populations, HDL-cholesterol concentration was not different between groups. PON1 activity was lower in white compared to black women (0.49±0.09 U/L vs 0.78±0.10 U/L, p<0.05). Obese black women had lower PAF-AH activity compared to obese white women (9.34±1.15 U/L vs 13.89±1.21 U/L, p<0.05). Compared to normal-weight women, obese women had lower large HDL, greater intermediate and small HDL. Compared to the sedentary control condition, exercise training was associated with a decrease in PON1 activity (-8.7±2.4% vs +1.1±3.0%, p<0.05), PAF-AH serum expression (-22.1±8.0% vs +16.9±9.8, p<0.005) and small HDL subclasses (-10.1±5.4% vs +15.7±6.6%, p<0.005). S1P content in HDL was lower in hypertensive and HF patients compared to controls (165 ± 55 vs 201 ± 73 pmol/mg, p < 0.05). HDL subclass distribution was different in hypertensive and HF patients with lower large HDL (48 ± 15 vs 63 ± 7%, p<0.005), higher intermediate (45 ± 7 vs 34 ± 5%, p<0.005) and small HDL (7 ± 9 vs 2 ± 4%, p<0.05). In contrast to HDL from control patients, HDL from all hypertensive patients failed to activate eNOS. Conclusions: In all three sample populations, there were associations between CVD risk factors and measures of HDL quality. HDL subclass distribution differences were associated with obesity and hypertensive heart failure, both in cross-sectional studies and in an exercise intervention study. In African sample populations, consideration of HDL quality rather than total HDL quantity may be a more sensitive marker to assess CVD risk
Association between ethnicity and obesity with high-density lipoprotein (HDL) function and subclass distribution
Abstract Background Obesity and low high-density lipoprotein-cholesterol (HDL-C) levels are associated with cardiovascular risk. Surprisingly, despite a greater prevalence of obesity and lower HDL concentrations than white women, black South African women are relatively protected against ischaemic heart disease. Methods We investigated whether this apparent discrepancy may be related to different HDL function and subclass distribution in black and white, normal-weight and obese South African women (n = 40). HDL functionality was assessed by measuring paraoxonase (PON) activity, platelet activating factor acetylhydrolase (PAF-AH) activity, Oxygen Radical Absorbance Capacity (ORAC) and quantification of the expression of vascular cell adhesion molecule in endothelial cells. PON-1 and PAF-AH expression was determined in isolated HDL and serum using Western blotting. Levels of large, intermediate and small HDL subclasses were measured using the Lipoprint® system. Results PON activity was lower in white compared to black women (0.49 ± 0.09 U/L vs 0.78 ± 0.10 U/L, p < 0.05), regardless of PON-1 protein levels. Obese black women had lower PAF-AH activity (9.34 ± 1.15 U/L vs 13.89 ± 1.21 U/L, p <0.05) and HDL-associated PAF-AH expression compared to obese white women. Compared to normal-weight women, obese women had lower large HDL, greater intermediate and small HDL; an effect that was more pronounced in white women than black women. There were no differences in antioxidant capacity or anti-inflammatory function across groups. Conclusions Our data show that both obesity and ethnicity are associated with differences in HDL functionality, while obesity was associated with decreases in large HDL subclass distribution. Measuring HDL functionality and subclass may, therefore, be important factors to consider when assessing cardiovascular risk
Exercise intervention alters HDL subclass distribution and function in obese women
Background
Obesity is associated with a change in high-density lipoprotein (HDL) function and subclass. Exercise training reduces cardiovascular risk in obese patients. We aimed to explore the effect of an exercise training stimulus on HDL functionality and subclass in obese women.
Methods
Thirty-two obese black South African women were randomly assigned to exercise (combined aerobic and resistance exercise) or control (no exercise) conditions for 12-weeks. Pre- and post-testing included venous blood sampling for analysis of lipid profile and HDL functionality, by measuring cellular cholesterol efflux capacity, reduction in endothelial vascular cell adhesion molecule (VCAM) expression (anti-inflammatory function), paraoxonase (PON) (antioxidative function) and platelet activating factor acetylhydrolase (PAF-AH) activities (anti-thrombotic function). PON-1 and PAF-AH expression were determined in serum and in isolated HDL using Western blotting. Levels of large, intermediate and small HDL subclasses were measured using the Lipoprint® system.
Results
Exercise training resulted in a decrease in body mass index (− 1.0 ± 0.5% vs + 1.2 ± 0.6%, p = 0.010), PON activity (− 8.7 ± 2.4% vs + 1.1 ± 3.0%, p = 0.021), PAF-AH serum expression (− 22.1 ± 8.0% vs + 16.9 ± 9.8, p = 0.002), and the distribution of small HDL subclasses (− 10.1 ± 5.4% vs + 15.7 ± 6.6%, p = 0.004) compared to controls. Exercise did not alter HDL cellular cholesterol efflux capacity and anti-inflammatory function.
Conclusions
These results demonstrate the potential for exercise training to modify HDL subclass distribution and HDL function in obese women.
Trial registration
Clinical trials number:
PACTR201711002789113
In vitro induction of quiescence in isolated primary human myoblasts
CITATION: Gudagudi, K. B. et al. 2020. In vitro induction of quiescence in isolated primary human myoblasts. Cytotechnology, 72:189–202. doi:10.1007/s10616-019-00365-8The original publication is available at https://www.springer.com/journal/10616/Adult skeletal muscle stem cells, satellite cells, remain in an inactive or quiescent state in vivo under physiological conditions. Progression through the cell cycle, including activation of quiescent cells, is a tightly regulated process. Studies employing in vitro culture of satellite cells, primary human myoblasts (PHMs), necessitate isolation myoblasts from muscle biopsies. Further studies utilizing these cells should endeavour to represent their native in vivo characteristics as closely as possible, also considering variability between individual donors. This study demonstrates the approach of utilizing KnockOut™ Serum Replacement (KOSR)-supplemented culture media as a quiescence-induction media for 10 days in PHMs isolated and expanded from three different donors. Cell cycle analysis demonstrated that treatment resulted in an increase in G1 phase and decreased S phase proportions in all donors (p 98% over time from day 0 to day 10. In contrast activation (CD56), proliferation (Ki67) and myogenic marker MyoD decreased, indicated de-differentiation. Induction of quiescence was accompanied in all three clones by fold change in p21 mRNA greater than 3.5 and up to tenfold. After induction of quiescence, differentiation into myotubes was not affected. In conclusion, we describe a method to induce quiescence in PHMs from different donors.https://link.springer.com/article/10.1007/s10616-019-00365-8Publishers versio
Association between ethnicity and obesity with high-density lipoprotein (HDL) function and subclass distribution
Comparative analysis of predictive equations for transfer processes in different porous structures
Thesis (PhD)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Research on transfer processes in various types of porous media has become important
for the optimization of high technology engineering devices and processes. In this study
the micro-structural parameters of different types of porous media, namely granular media,
foamlike media and fibre beds, are characterized and quantified. Existing analytical
modelling procedures for the three different types of porous media have been unified and
refined to improve their predictive capabilities. Deterministic equations are proposed for
predicting the streamwise pressure gradient, permeability and inertial coefficient of each
type of porous medium. The equations are applicable over the entire porosity range and
steady laminar flow regime and well suited as drag models in numerical computations.
It is shown that the improved granular model can be regarded as qualitative and quantitative
proof of the extensively used semi-empirical Ergun equation. The proposed model
is used to provide physical meaning to the empirical coefficients. An Ergun-type equation
is also proposed for foamlike media by remodelling the interstitial geometric configuration
and accompanying flow conditions.
The range of applicability of the existing foam model has been extended by incorporating
the effect of developing flow in the pressure drop prediction. An equation is proposed
in which the variation in the cross-sectional shape of the fibres can be incorporated into
the interstitial form drag coefficient used in the foam model. This serves as an improvement
on the constant value previously used. The existing foam model is also adapted
to account for anisotropy resulting from compression. Two case studies are considered,
namely compression of a non-woven glass fibre filter and compression of a soft polyester
fibre material. The significant effect of compression on permeability is illustrated. In
each case study the permeability values range over more than an order of magnitude for
the narrow porosity ranges involved. The pressure drop prediction of the foam model is
furthermore adapted to account for the combined effects of compression and developing
flow. The newly proposed model diminishes the significant over-prediction of the existing
foam model.
An equation is furthermore proposed for predicting the permeability of Fontainebleau
sandstones in which the effect of blocked throats is accounted for. Lastly, equations are
proposed for predicting diffusivity ratios of unconsolidated arrays of squares and cubes.
The prediction of the diffusivity ratio proposed in the present study, as opposed to model
predictions from the literature, takes into account diffusion that may take place in stagnant
fluid volumes. It is shown that a specific weighted average model proposed in the literature
is not adequate to predict the diffusivity ratio of fully staggered arrays of squares, since it is
shown not to be applicable to rectangular unit cells. Instead a new weighted average model
is proposed which is applicable over the entire porosity range and for both staggered and
non-staggered arrays of solid squares and cubes. The proposed weighted average model
provides satisfactory agreement with experimental data from the literature and numerical
data generated in the present study.AFRIKAANSE OPSOMMING: Navorsing op oordragsprosesse in verskeie tipes poreuse media het belangrik geword vir die
optimisering van ho¨e-tegnologie ingenieurstoestelle- en prosesse. In hierdie studie word die
mikro-struktuur parameters van verskillende tipes poreuse media, naamklik korrelagtige
media, sponsatige media en veselbeddens gekarakteriseer en gekwantifiseer. Bestaande
analitiese modelleringsprosedures vir die drie verskillende tipes poreuse media is verenig
en verfyn om die voorspelbare bekwaamheid daarvan te verbeter. Deterministiese vergelykings
is voorgestel vir die voorspelling van die stroomsgewyse gradi¨ent, permeabiliteit en
inersi¨ele ko¨effisi¨ent van elke tipe poreuse medium. Die vergelykings is geldig oor die hele
porositeitsgrens en gestadigde laminˆere vloeigrens en goed geskik as weerstandsmodelle
in numeriese berekeninge.
Dit is aangetoon dat die verbeterde korrelmodel beskou kan word as kwalitatiewe en
kwantitatiewe bewys van die ekstensiewe gebruikte semi-empiriese Ergun vergelyking. Die
voorgestelde model is gebruik om fisiese betekenis aan die empiriese ko¨effisi¨ente te gee. ’n
Ergun-tipe vergelyking is ook voorgestel vir sponsagtige media deur hermodellering van
die tussenruimtelike geometriese konfigurasie en gepaardgaande vloeikondisies.
Die grense van toepaslikheid van die bestaande sponsmodel is uitgebrei deur die inkorporering
van die effek van ontwikkelende vloei in die voorspelling van die drukval. ’n
Vergelyking is voorgestel waarin die variasie in die deursnit vorm van die vesels ingesluit is
in die sponsmodel. Dit dien as verbetering op die konstante waarde wat voorheen gebruik
is. Die bestaande sponsmodel is ook aangepas om voorsiening te maak vir anisotropie
as gevolg van kompressie. Twee gevallestudies is oorweeg, naamlik kompressie van ’n
nie-geweefde glasvesel filter en kompressie van ’n sagte polyester veselmateriaal. Die
beduidende effek van kompressie op permeabiliteit is aangetoon. In elke gevallestudie
strek die permeabiliteit waardes oor meer as ’n grootte orde vir die skrale porositeitgrense
betrokke. Die drukvalvoorspelling van die sponsmodel is verder aangepas om voorsiening
te maak vir die gekombineerde effekte van kompressie en ontwikkelende vloei. Die
nuwe voorgestelde model verminder die beduidende oor-voorspelling van die bestaande
sponsmodel.
’n Vergelyking is verder voorgestel vir die voorspelling van die permeabiliteit van Fontainebleau
sandsteen waarin die effek van geblokte porie¨e in ag geneem is. Laastens is vergelykings
voorgestel vir die voorspelling van die diffusiwiteitsverhoudings van nie-konsoliderende
rangskikkings van vierkante en kubusse. Die diffusiwiteitsverhouding voorspel in die
huidige studie, teenoor modelvoorspellings vanaf die literatuur, neem diffusie in ag wat
plaasvind in die stagnante vloeistofvolumes. Dit is aangetoon dat ’n geweegde gemiddelde
model, voorgestel in die literatuur, nie in staat is om die diffusiwiteitsverhouding
van ten volle verspringende rangskikkings van vierkante te voorspel nie, aangesien dit nie
toepaslik is vir reghoekige eenheidselle nie. ’n Nuwe geweegde model is in plaas daarvan
voorgestel wat toepaslik is oor die hele porositeitsgrens en vir beide verspringende en nieverspringende
rangskikkings van soliede vierkante en kubusse. Die voorgestelde geweegde
gemiddelde model bied bevredigende ooreenstemming met eksperimentele data uit die
literatuur en numeriese data gegenereer in die huidige studie
Incomplete Faraday cage effect of helicopters used in platform live-line maintenance.
The use of helicopters for maintenance
on live overhead transmission lines has become a
realistic option. The helicopter blades, body and
working platform can be seen as creating an
incomplete Faraday cage, which may be an
enhancement to live-line worker safety. This
paper simulates the condition using a Faraday
cage which can be dismantled, in a controlled
laboratory environment to ascertain the
effectiveness of apparatus
Bioprospecting in the Southern Ocean and Antarctica A review of the issues and options
Bioprospecting is occurring in the Southern Ocean and Antarctica. There is no clear jurisdiction
that currently governs bioprospecting in the Antarctic. Treaty parties are just beginning to discuss
bioprospecting and it possible implications at various forums but there has been no agreement to
date that it is a problem and a response is needed. This paper reviews the issues and options
that have currently been identifie
- …