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natural fractals

Indresh Yadav, Sugam Kumar, Vinod K Aswal, Joachim Kohlbrecher
The pH-dependent structure and interaction of anionic silica nanoparticles (diameter 18 nm) with two globular model proteins-lysozyme and bovine serum albumin (BSA) have been studied. Cationic lysozyme adsorbs strongly on the nanoparticles and the adsorption follows an exponential growth as a function of lysozyme concentration, where the saturation value increases with pH approaching towards the isoelectric point (IEP) of lysozyme. In contrast, irrespective of the pH, anionic BSA does not show any adsorption...
January 12, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Feng Li, Dejun Sun, Tao Wu, Yujiang Li
In this work, aggregation and deposition of in situ formed magnesium hydroxide (IFM) in the presence of hydrolyzed polyacrylamide (HPAM) were investigated. Relative concentrations of interactants, as well as other experimental conditions, were changed to elucidate the interaction mechanisms from microscopic to macroscopic levels. Light scattering measurements were used to investigate the aggregation kinetics, fractal dimension, and collision efficiency of the aggregates on a microscopic level. Electrophoretic mobility and TEM were utilized to measure the charging properties and morphologies of aggregates, respectively...
January 11, 2017: Soft Matter
Denis S Grebenkov
We derive a general exact formula for the mean first passage time (MFPT) from a fixed point inside a planar domain to an escape region on its boundary. The underlying mixed Dirichlet-Neumann boundary value problem is conformally mapped onto the unit disk, solved exactly, and mapped back. The resulting formula for the MFPT is valid for an arbitrary space-dependent diffusion coefficient, while the leading logarithmic term is explicit, simple, and remarkably universal. In contrast to earlier works, we show that the natural small parameter of the problem is the harmonic measure of the escape region, not its perimeter...
December 23, 2016: Physical Review Letters
Brett F BuSha, George Banis
Human breathing patterns contain both temporal scaling characteristics, and an innately random component. A stochastic and mathematically integrative model of breathing (SIMB) that simulated the natural random and fractal-like pattern of human breathing was designed using breath-to-breath interval (BBI) data recorded from 14 healthy subjects. Respiratory system memory was estimated with autocorrelation, and a probability density function (PDF) was created by fitting a polynomial curve to each normalized BBI sequence histogram...
January 3, 2017: Respiratory Physiology & Neurobiology
Hyun-A Kim, Byung-Tae Lee, So-Young Na, Kyoung-Woong Kim, James F Ranville, Soon-Oh Kim, Eunhye Jo, Ig-Chun Eom
The single particle-inductively coupled plasma-mass spectrometry was applied to characterize the aggregates of AgNPs. was applied to characterize the aggregates of AgNPs. Two sizes of citrate-AgNPs and PVP-AgNPs were used at relatively high and predicted environmental concentrations under various ionic strengths. Citrate-AgNP aggregated with increases in the ionic strength, whereas PVP-AgNPs were sterically stable. The critical coagulation concentrations were 85 mM and 100 mM NaNO3 for 60 nm and 100 nm citrate-AgNPs at 2 mg L(-1) as total Ag obtained by dynamic light scattering (DLS)...
December 19, 2016: Chemosphere
Qingli Dong, Yong Wang, Peizhi Li
Compared with the traditional method of detrended fluctuation analysis, which is used to characterize fractal scaling properties and long-range correlations, this research provides new insight into the multifractality and predictability of a nonstationary air pollutant time series using the methods of spectral analysis and multifractal detrended fluctuation analysis. First, the existence of a significant power-law behavior and long-range correlations for such series are verified. Then, by employing shuffling and surrogating procedures and estimating the scaling exponents, the major source of multifractality in these pollutant series is found to be the fat-tailed probability density function...
December 21, 2016: Environmental Pollution
Jianrong Chen, Hongjun Lin, Liguo Shen, Yiming He, Meijia Zhang, Bao-Qiang Liao
Quantification of interfacial interaction with randomly rough surface is the prerequisite to quantitatively understand and control the interface behaviors such as adhesion, flocculation and membrane fouling. In this study, it was found that membrane surface was randomly rough with obvious fractal characteristics. The randomly rough surface of membrane could be well reconstructed by the fractal geometry represented by a modified Weierstrass-Mandelbrot function. A novel method, which combined composite Simpson's approach, surface element integration method and approximation by computer programming, was developed...
December 9, 2016: Bioresource Technology
Sung Kyu Maeng, Thomas C Timmes, Hyun-Chul Kim
Two different quaternary amine polymers were examined as primary coagulants for the removal of natural organic matter (NOM) and concurrent production of flocs favorable for downstream membrane separation. The primary issue explored was the relationship between various coagulation conditions on the floc characteristics and the subsequent performance of microfiltration when filtering coagulated NOM. The size distribution and morphological properties of flocs formed through the coagulation of NOM were characterized and the effects of polymer type and dose on these characteristics were also examined...
December 26, 2016: Environmental Technology
S Ranjitkar, A Turan, C Mann, G A Gully, M Marsman, S Edwards, J A Kaidonis, C Hall, D Lekkas, P Wetselaar, A H Brook, F Lobbezoo, G C Townsend
Scale-sensitive fractal analysis of high-resolution 3-dimensional surface reconstructions of wear patterns has advanced our knowledge in evolutionary biology, and has opened up opportunities for translatory applications in clinical practice. To elucidate the microwear characteristics of attrition and erosion in worn natural teeth, we scanned 50 extracted human teeth using a confocal profiler at a high optical resolution (X-Y, 0.17 µm; Z < 3 nm). Our hypothesis was that microwear complexity would be greater in erosion and that anisotropy would be greater in attrition...
December 7, 2016: Journal of Dental Research
Tanveer Ul Islam, Prasanna S Gandhi
Nature, in quest for the best designs has shaped its vital systems into fractal geometries. Effectual way of spontaneous fabrication of scalable, ordered fractal-like structures by controlling Saffman-Taylor instability in a lifted Hele-Shaw cell is deployed here. In lifted Hele-Shaw cell uncontrolled penetration of low-viscosity fluid into its high-viscosity counterpart is known to develop irregular, non-repeatable, normally short-lived, branched patterns. We propose and characterize experimentally anisotropies in a form of spatially distributed pits on the cell plates to control initiation and further penetration of non-splitting fingers...
November 16, 2016: Scientific Reports
Shazia Nafis, Kalaiarasan Ponnusamy, Mohammad Husain, R K Brojen Singh, Rameshwar N K Bamezai
An experimentally validated set of apoptosis-regulatory proteins was subjected to network analysis, depicting a scale-free hierarchical fractal network. The power-law distribution of the various topological properties of the network revealed the fractal nature of the network, a signature of self-organization of the network where the network maintained the democratic constitution of nodes at various levels and showed the absence of the centrality-lethality control system. Even though network breakdown under the absence of the centrality-lethality rule of hub removal did not happen, the change in the topological properties of the network could be observed...
October 18, 2016: Molecular BioSystems
Zoey J Isherwood, Mark M Schira, Branka Spehar
Natural scenes share a consistent distribution of energy across spatial frequencies (SF) known as the 1/f(α) amplitude spectrum (α≈0.8-1.5, mean 1.2). This distribution is scale-invariant, which is a fractal characteristic of natural scenes with statistically similar structure at different spatial scales. While the sensitivity of the visual system to the 1/f properties of natural scenes has been studied extensively using psychophysics, relatively little is known about the tuning of cortical responses to these properties...
October 11, 2016: NeuroImage
Emerson R Silva, Gary Cooney, Ian W Hamley, Wendel A Alves, Shannon Lee, Brendan F O'Connor, Mehedi Reza, Janne Ruokolainen, Dermot Walls
We describe in depth the structure of complexes formed between DNA and two classes of arginine-containing peptide amphiphiles, namely, the lipopeptide PRW-C16 (P = proline, R = arginine, W = tryptophan, C16 = C16 : 0 alkyl chain) and the bolaamphiphile RFL4FR (R = arginine, F = phenylalanine, L = leucine). A combination of X-ray and neutron scattering provided unprecedented insights into the local structure of these complexes. Lipopeptide-based complexes self-assembled into layered structures with large-scale fractal features, hosting DNA in the interstices...
November 16, 2016: Soft Matter
Lifen Wang, Jianguo Wen, Huaping Sheng, Dean J Miller
Fractals are commonly observed in nature and elucidating the mechanisms of fractal-related growth is a compelling issue for both fundamental science and technology. Here we report an in situ electron microscopy study of dynamic fractal growth of platinum during electrodeposition in a miniaturized electrochemical cell at varying growth conditions. Highly dendritic growth - either dense branching or ramified islands - are formed at the solid-electrolyte interface. We show how the diffusion length of ions in the electrolyte influences morphology selection and how instability induced by initial surface roughness, combined with local enhancement of electric field, gives rise to non-uniform branched deposition as a result of nucleation/growth at preferred locations...
October 6, 2016: Nanoscale
Rodrigo Echeveste, Claudius Gros
The study of balanced networks of excitatory and inhibitory neurons has led to several open questions. On the one hand it is yet unclear whether the asynchronous state observed in the brain is autonomously generated, or if it results from the interplay between external drivings and internal dynamics. It is also not known, which kind of network variabilities will lead to irregular spiking and which to synchronous firing states. Here we show how isolated networks of purely excitatory neurons generically show asynchronous firing whenever a minimal level of structural variability is present together with a refractory period...
2016: Frontiers in Computational Neuroscience
Anil Koklu, Ahmet C Sabuncu, Ali Beskok
Electrode polarization at the electrolyte/electrode interface is often undesirable for bio-sensing applications, where charge accumulated over an electrode at constant potential causes large potential drop at the interface and low measurement sensitivity. In this study, novel rough electrodes were developed for decreasing electrical impedance at the interface. The electrodes were fabricated using electrochemical deposition of gold and sintering of gold nanoparticles. The performances of the gold electrodes were compared with platinum black electrodes...
July 1, 2016: Electrochimica Acta
Parul Dubey, Sugam Kumar, Vinod K Aswal, Sapna Ravindranathan, Pattuparambil R Rajamohanan, Asmita Prabhune, Anuya Nisal
Silk fibroin (SF) protein, produced by silkworm Bombyx mori, is a promising biomaterial, while sophorolipid (SL) is an amphiphilic functional biosurfactant synthesized by nonpathogenic yeast Candida bombicola. SL is a mixture of two forms, acidic (ASL) and lactonic (LSL), which when added to SF results in accelerated gelation of silk fibroin. LSL is known to have multiple biological functionalities and hence hydrogels of these green molecules have promising applications in the biomedical sector. In this work, SANS, NMR, and rheology are employed to examine the assembling properties of individual and mixed SLs and their interactions with SF to understand the mechanism that leads to rapid gelation...
October 10, 2016: Biomacromolecules
Hari Katepalli, Vijay T John, Anubhav Tripathi, Arijit Bose
Using fumed and spherical silica particles of similar hydrodynamic size, we investigated the effects of particle shape and inter-particle interactions on the formation, stability and rheology of bromohexadecane-in-water Pickering emulsions. The interparticle interactions were varied from repulsive to attractive by modifying the salt concentration in the aqueous phase. Optical microscope images revealed smaller droplet sizes for the fumed silica stabilized emulsions. All the emulsions remained stable for several weeks...
January 1, 2017: Journal of Colloid and Interface Science
Ying Li, Ye He, Yu Zhang
OBJECTIVE: Biological processes actually are a dynamic molecular process over time. Time course gene expression experiments provide opportunities to explore patterns of gene expression change over a time and understand the dynamic behavior of gene expression, which is crucial for study on development and progression of biology and disease. Analysis of the gene expression time-course profiles has not been fully exploited so far. It is still a challenge problem. We propose a novel shape-based mixture model clustering method for gene expression time-course profiles to explore the significant gene groups...
November 2016: Mathematical Biosciences
Emile Franc Doungmo Goufo
After having the issues of singularity and locality addressed recently in mathematical modelling, another question regarding the description of natural phenomena was raised: How influent is the second parameter β of the two-parameter Mittag-Leffler function Eα,β(z), z∈ℂ? To answer this question, we generalize the newly introduced one-parameter derivative with non-singular and non-local kernel [A. Atangana and I. Koca, Chaos, Solitons Fractals 89, 447 (2016); A. Atangana and D. Bealeanu (e-print)] by developing a similar two-parameter derivative with non-singular and non-local kernel based on Eα , β(z)...
August 2016: Chaos
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