Complexity in Biological Organization: Deconstruction (and Subsequent Restating) of Key Concepts.

The "magic" word complexity evokes a multitude of meanings that obscure its real sense. Here we try and generate a bottom-up reconstruction of the deep sense of complexity by looking at the convergence of different features shared by complex systems. We specifically focus on complexity in biology but stressing the similarities with analogous features encountered in inanimate and artefactual systems in order to track an integrative path toward a new "mainstream" of science overcoming the actual fragmentation of scientific culture.

Adhesion of Rhodococcus ruber IEGM 342 to polystyrene studied using contact and non-contact temperature measurement techniques.

Adhesion of industrially important bacteria to solid carriers through the example of actinobacterium Rhodococcus ruber IEGM 342 adhered to polystyrene was studied using real-time methods, such as infrared (IR) thermography and thermometry with platinum resistance (PR) detectors. Dynamics of heat rate and heat production was determined at early (within first 80 min) stages of rhodococcal cell adhesion. Heat rate was maximal (1.8 × 10-3-2.7 × 10-3 W) at the moment of cell loading. Heat production was detected for the entire length of adhesion, and its dynamics depended on concentration of rhodococcal cells. At high (1 × 1010 CFU/ml) cell concentration, a stimulative (in 1.7 and 1.4 times consequently) effect of polystyrene treatment with Rhodococcus-biosurfactant on the number of adhered rhodococcal cells and cumulative heat production at rhodococcal cell adhesion was revealed. The values of heat flows (heat rate 0.3 × 10-3-2.7 × 10-3 W, heat production up to 8.2 × 10-3 J, and cumulative heat production 0.20-0.53 J) were 5-30 times higher than those published elsewhere that indicated high adhesive activity of R. ruber IEGM 342 towards polystyrene. To analyze experimental results and predict effects of boundary conditions on the temperature distribution, a mathematical model for heating a polystyrene microplate with distributed heat sources has been developed. Two independent experimental methods and the numerical modeling make it possible to verify the experimental results and to propose both contact and non-contact techniques for analyzing kinetics of bacterial adhesion.

Biosurfactant-enhanced immobilization of hydrocarbon-oxidizing Rhodococcus ruber on sawdust.

Immobilization of microorganisms on/in insoluble carriers is widely used to stabilize functional activity of microbial cells in industrial biotechnology. We immobilized Rhodococcus ruber, an important hydrocarbon degrader, on biosurfactant-coated sawdust. A biosurfactant produced by R. ruber in the presence of liquid hydrocarbons was found to enhance rhodococcal adhesion to solid surfaces, and thus, it was used as a hydrophobizing agent to improve bacterial attachment to a sawdust carrier. Compared to previously used hydrophobizers (drying oil and n-hexadecane) and emulsifiers (methyl- and carboxymethyl cellulose, poly(vinyl alcohol), and Tween 80), Rhodococcus biosurfactant produced more stable and homogenous coatings on wood surfaces, thus resulting in higher sawdust affinity to hydrocarbons, uniform monolayer distribution of immobilized R. ruber cells (immobilization yield 29-30 mg dry cells/g), and twofold increase in hydrocarbon biooxidation rates compared to free rhodococcal cells. Two physical methods, i.e., high-resolution profilometry and infrared thermography, were applied to examine wood surface characteristics and distribution of immobilized R. ruber cells. Sawdust-immobilized R. ruber can be used as an efficient biocatalyst for hydrocarbon transformation and degradation.

Critical Dynamics of Defects and Mechanisms of Damage-Failure Transitions in Fatigue.

An experimental methodology was developed for estimating a very high cycle fatigue (VHCF) life of the aluminum alloy AMG-6 subjected to preliminary deformation. The analysis of fatigue damage staging is based on the measurement of elastic modulus decrement according to "in situ" data of nonlinear dynamics of free-end specimen vibrations at the VHCF test. The correlation of fatigue damage staging and fracture surface morphology was studied to establish the scaling properties and kinetic equations for damage localization, "fish-eye" nucleation, and transition to the Paris crack kinetics. These equations, based on empirical parameters related to the structure of the material, allows us to estimate the number of cycles for the nucleation and advance of fatigue crack.

Label-Free Single Cell Viability Assay Using Laser Interference Microscopy.

Laser interference microscopy (LIM) is a promising label-free method for single-cell research applicable to cell viability assessment in the studies of mammalian cells. This paper describes the development of a sensitive and reproducible method for assessing cell viability using LIM. The method, based on associated signal processing techniques, has been developed as a result of real-time investigation in phase thickness fluctuations of viable and non-viable MCF-7 cells, reflecting the presence and absence of their metabolic activity. As evinced by the values of the variable vc, this variable determines the viability of a cell only in the attached state (vc exceeds 20 nm2 for viable attached cells). The critical value of the power spectrum slope ßc of the phase thickness fluctuations equals 1.00 for attached MCF-7 cells and 0.71 for suspended cells. The slope of the phase fluctuations' power spectrum for MCF-7 cells was determined to exceed the threshold value of ßc for a living cell, otherwise the cell is dead. The results evince the power spectrum slope as the most appropriate indicator of cell viability, while the integrated evaluation criterion (vc and ßc values) can be used to assay the viability of attached cells.

Characteristic Features of Ultrafine-Grained Ti-45 wt.% Nb Alloy under High Cycle Fatigue.

The paper presents the results of fatigue-testing ultrafine-grained and coarse-grained Ti-45 wt.% Nb alloy samples under very high cycle fatigue (gigacycle regime), with the stress ratio R = -1. The ultrafine-grained (UFG) structure in the investigated alloy was formed by the two-stage SPD method, which included multidirectional forging (abc-forging) and multipass rolling in grooved rollers, with further recrystallization annealing. The UFG structure of the Ti-45 wt.% Nb alloy samples increased the fatigue limit under the high-cycle fatigue conditions up to 1.5 times compared with that of the coarse-grained (CG) samples. The infrared thermography method was applied to investigate the evolution of temperature fields in the samples under cyclic loading. Based on numerical morphology analysis, the scale invariance (the Hurst exponent) and qualitative differences for UFG and CG structures were determined. The latter resulted from the initiation and propagation of fatigue cracks in both ultra-fine grained and coarse-grained alloy samples under very high-cycle fatigue loading.

Comparative Multifractal Analysis of Dynamic Infrared Thermograms and X-Ray Mammograms Enlightens Changes in the Environment of Malignant Tumors.

There is growing evidence that the microenvironment surrounding a tumor plays a special role in cancer development and cancer therapeutic resistance. Tumors arise from the dysregulation and alteration of both the malignant cells and their environment. By providing tumor-repressing signals, the microenvironment can impose and sustain normal tissue architecture. Once tissue homeostasis is lost, the altered microenvironment can create a niche favoring the tumorigenic transformation process. A major challenge in early breast cancer diagnosis is thus to show that these physiological and architectural alterations can be detected with currently used screening techniques. In a recent study, we used a 1D wavelet-based multi-scale method to analyze breast skin temperature temporal fluctuations collected with an IR thermography camera in patients with breast cancer. This study reveals that the multifractal complexity of temperature fluctuations superimposed on cardiogenic and vasomotor perfusion oscillations observed in healthy breasts is lost in malignant tumor foci in cancerous breasts. Here we use a 2D wavelet-based multifractal method to analyze the spatial fluctuations of breast density in the X-ray mammograms of the same panel of patients. As compared to the long-range correlations and anti-correlations in roughness fluctuations, respectively observed in dense and fatty breast areas, some significant change in the nature of breast density fluctuations with some clear loss of correlations is detected in the neighborhood of malignant tumors. This attests to some architectural disorganization that may deeply affect heat transfer and related thermomechanics in breast tissues, corroborating the change to homogeneous monofractal temperature fluctuations recorded in cancerous breasts with the IR camera. These results open new perspectives in computer-aided methods to assist in early breast cancer diagnosis.

Wavelet-based multifractal analysis of dynamic infrared thermograms to assist in early breast cancer diagnosis.

Breast cancer is the most common type of cancer among women and despite recent advances in the medical field, there are still some inherent limitations in the currently used screening techniques. The radiological interpretation of screening X-ray mammograms often leads to over-diagnosis and, as a consequence, to unnecessary traumatic and painful biopsies. Here we propose a computer-aided multifractal analysis of dynamic infrared (IR) imaging as an efficient method for identifying women with risk of breast cancer. Using a wavelet-based multi-scale method to analyze the temporal fluctuations of breast skin temperature collected from a panel of patients with diagnosed breast cancer and some female volunteers with healthy breasts, we show that the multifractal complexity of temperature fluctuations observed in healthy breasts is lost in mammary glands with malignant tumor. Besides potential clinical impact, these results open new perspectives in the investigation of physiological changes that may precede anatomical alterations in breast cancer development.