Analysis and modeling of biological systems using fractal geometry

Fractal objects which, by definition, are objects that have scale-invariant shapes and fractional scaling dimensions (fractal dimension) with magnitudes related to the complexity of the objects, are ubiquitous in nature. In particular, many biological structures and systems have fractal properties and therefore may be well studied and modelled using fractal geometry. In the box counting algorithm, one of several different approaches to calculate the fractal dimension, one determines, for several values of, the number of boxesN() with side length needed to completely cover the studied object. IfN() andr are found to be related by the power law relationshipN(r) r ^–D, whereD is the scaling dimension, and ifD is a non-integer, then the object is fractal andD is the fractal dimension.In certain circumstances in which one may need to calculate the fractal dimension of a three-dimensional fractal from a two-dimensional projection (e.g. an X-ray), a new mathematical relationship may be utilized to obtain the actual dimensionD; it readsD=–log[1–(1–R ^2– D _p) ^R ]/logR + 3, whereD _p is the fractal dimension of the two-dimensional planar projection of the object andR is the box size used in calculating the box-counting dimension.Fractal dimension calculations have been found to be particularly useful as quantitative indices of the degree of coronary vascularity and the degree of heart interbeat interval variability. Fractal growth models such as diffusion limited aggregation (DLA) can be used to model artery growth.To sum up, fractal geometry is very useful in studying and modeling certain scale-invariant biological structures or systems which may not be easily described with Euclidean shapes.     

GPC study of ethylene-propylene copolymers combined with viscometry and IR spectroscopy

Summary By combining GPC fractionation with IR spectroscopy of ethylene-propylene copolymer (EP) samples, it has been shown that copolymer composition of EP's used in this study does not dep-end on molecular weight. Thus, contrary to earlier investigations by others, molecular weight distributions (MWD) and averages of EP's have been determined by using only experimental data such as GPC traces, universal calibration curve of GPC, and intrinsic viscosities. A comparative study has been carried out by using the MV method (called median value method) and the method of Ogawa and Inaba (OI method) for determination of MWD's and molecular weight averages of EP's. Application of the MV method results in lower molecular weight averages than the use of the equations proposed by Ogawa and Inaba for calculation of Mark-Houwing constants of EP's. However, polydispersities were found to be the same in both methods. The MV method also yields composition depending reliable pairs of Mark-Houwink constants, a and K, for EP's in 1,2,4-trichloro-benzene at 135 °C.     

The colour of monolithic zirconia restorations determined by spectrophotometric examination

ABSTRACT

Objective: The aim of this in vitro study is to examine the optical effects of monolithic zirconia of different translucency and thickness, combined with substrates of different colours. Materials and methods: Zirconia specimens of two colours (A2P1, WHITE) were used for the study, three try-in pastes (Variolink Esthetic); substrates were prepared from nine types of materials (six VITA SIMULATE, three metals). Measurements were carried out at the Faculty of Atomic Physics of the Technical University of Budapest with the state-of-the-art PerkinElmer® Lambda 1050 spectrophotometer. Results: The colouring of zirconia has a major effect on dE values resulting in different colour perceptibility and acceptability. Try-in pastes, however, have no significant effects overall. Conclusion: Applying coloured zirconia is highly eligible for preparing aesthetic crowns as their substrate-covering effect makes it possible to reproduce the desired colour. Uncoloured zirconia nonetheless is unaffected by the substrate material, especially above a certain layer thickness.     

Influence of chlorine-water equilibria on the electrochemical destruction of thiocarbamate herbicides in NaCl solutions

The electrolytic destruction of thiocarbamates in NaCl solutions takes place mainly through indirect electrolysis with Cl₂, HOCl, ClO⁻ and other oxidising species. The electrochemical destruction of thiocarbamates EPTC and Vernolate was studied in different Cl₂, HOCl, ClO⁻ domains in chlorine–water equilibrium. Differences were found in both destruction rate and in intermediate and end products. Complete mineralisation can be achieved in ClO⁻ domain, where both total organic carbon (TOC) content and chemical oxygen demand (COD) are continuously decreasing and biodegradability is increasing during electrolysis. UV irradiation considerably accelerates the destruction process, i.e. the electrochemical destruction of thiocarbamate Vernolate.     

Fetal phonocardiography--past and future possibilities

The paper presents an overview of the 15 year long development of fetal phonocardiography including the works on the applied signal processing methods for identification of sound components. Based on the improvements achieved on this field, the paper shows that beyond the traditional CTG test the phonocardiography may be successfully applied for long-term fetal measurements and home monitoring. In addition, by indication of heart murmurs based on a comprehensive analysis of the recorded heart sound congenital heart defects can also be detected together with additional features in the third trimester. This makes an early widespread screening possible combined with the prescribed CTG test even at home using a telemedicine system.     

Stability of sunflower 2S albumins and LTP to physiologically relevant in vitro gastrointestinal digestion

In order for a protein to elicit a systemic allergic response it must reach the circulatory system through the intestinal mucosa as a sufficiently large fragment with adequate structural integrity. Sunflower LTP and 2S albumins (SFA8 and three mixed fractions of Alb1 and Alb2) were digested in simulated gastric fluid (SGF) for 2 h and the conditions were then changed to mimic the intestinal environment for a further 2 h digestion. The effects of phosphatidylcholine (PC) and emulsification on the digestibility of the proteins were investigated. PC protected all of the proteins studied against both gastric and intestinal digestive enzymes but to different extents. Emulsification of SFA8 resulted in strong protection against digestion, which was further enhanced by the presence of PC in the SGF. These results highlight the importance of considering real food structures such as emulsified systems and also the gastrointestinal environment that proteins are exposed to once consumed when assessing allergenicity.     

Effects of incorporated amaranth albumins on the functional properties of wheat dough

BACKGROUND: Recent developments in micro‐scale testing methodology and in methods modelling the effects of native forms of constituents by in vitro methods have provided a new approach to study the impact of added foreign proteins on dough end‐use quality. Amaranth (Amaranthus) is a member of the pseudo‐cereal family, whose storage proteins have superior nutritional quality due to their essential amino acid composition. The aim of this project was to study the effects of the incorporated amaranth albumin proteins on the rheological properties of the wheat dough. RESULTS: The mixing time requirements, dough strength and stability of the reconstructed dough increased proportionally with the amount (1, 3 and 5%) of amaranth albumin proteins incorporated. These results were supported by measurements on the non‐extractable polymeric protein ratio of the dough indicating the change in polymer size distribution. CONCLUSION: It was demonstrated that amaranth albumin proteins are capable of interacting with gluten proteins through disulfide bonds, showing similar effects to the individual glutenin subunits of wheat flour proteins. Improvements in dough strength and stability without a substantial increase in the mixing requirements are of great significance for developing energy saving technologies in the baking industry. Copyright © 2009 Society of Chemical Industry     

In vitro microbial metabolism of fumonisin B1

There is a lack of information on the effect of swine caecal microbiota on fumonisin metabolism. In this in vitro study, the biotransformation of fumonisin B₁ (FB₁) by the gut microbiota of adult, healthy pigs was examined. Suspensions of caecal contents and McDougall buffer solution were incubated anaerobically with pure FB₁ for 0, 12, 24, 48 and 72 h. After 48 h, the conversion of FB₁ to partially hydrolysed FB₁ (46%) was nearly equal to the percentage ratio of FB₁, while by 72 h it was 49%. In vitro, the conversion of fumonisin B₁ to aminopentol was less than 1%. The results show that the caecal microbiota are capable of transforming fumonisin B₁ to the above metabolites. Further studies on FB₁ metabolism in the small intestine are clearly justified.     

Sources of doubt: actors,forums, and language of climate change skepticism

Scientometrics - The paper investigates the reference corpus of a climate change contrarian report. We categorized the journal abstracts according to the endorsement positions on anthropogenic...