Undulation Instability of Epithelial Tissues

Treating the epithelium as an incompressible fluid adjacent to a viscoelastic stroma, we find a novel hydrodynamic instability that leads to the formation of protrusions of the epithelium into the stroma. This instability is a candidate for epithelial fingering observed in vivo. It occurs for sufficiently large viscosity, cell-division rate and thickness of the dividing region in the epithelium. Our work provides physical insight into a potential mechanism by which interfaces between epithelia and stromas undulate, and potentially by which tissue dysplasia leads to cancerous invasion.Comment: 4 pages, 3 figure

Protected group control system for mobile robots

The purpose of this work is to present a secure group control system for ground mobile robots. The paper includes the analysis of existing group control algorithms, a description of the implementation of some of the algorithms, their testing and analysis of characteristics. When we solve the problem, we adhere to the following aspects: The multivariance of simulated situations, the feasibility of algorithms within the framework of existing computer systems and their applicability within the framework of real group control systems, the use of cryptographic information security tools using distributed methods, the development of a model for group control of robots and testing of developed solutions should be carried out using a simulator, approbation of the developed solutions is carried out using a full-scale model, which includes a set of single-board computers, between which a wireless network is organized, robots perform the main task of analyzing the terrain and building a terrain map, while the terrain map should be distributed between robots and updated periodically, robots must be able to avoid obstacles and collisions with each other, perform the task of moving towards the goal and the task of following the group leader. Security solutions must ensure the property of integrity, proof of authorship, and trust in the data. Implementing the choice of the group leader must also provide the ability to select a trusted entity as the group leader

Procjena cikličkih krivulja naprezanje-deformacija niskolegiranog čelika na osnovi tvrdoće

This article describes investigations into the existence of correlation between experimentally determined cyclic parameters and hardness of quenched and tempered representative low-alloy steel 42CrMo4. A good correlation was found to exist between cyclic strength coefficient K’ and Brinell hardness HB, but not between cyclic strain hardening exponent n‘ and hardness HB. Nevertheless, good agreement between calculated and experimental cyclic stress-strain curves shows that cyclic parameters i.e. cyclic stress-strain curves of the investigated steel can be successfully estimated from its hardness.U radu je istraženo postojanje korelacije između eksperimentalnih vrijednosti cikličkih parametara i tvrdoće poboljšanog niskolegiranog čelika 42CrMo4. Ustanovljena je dobra koreliranost koeficijenta cikličke čvrstoće K’ i Brinellove tvrdoće HB, ali ne i eksponenta cikličkog deformacijskog očvršćivanja n’ i tvrdoću HB. Usprkos tome, dobivenim cikličkim krivuljama naprezanje-deformacija pokazano je da se ciklički parametri i njima definirane cikličke krivulje naprezanje-deformacija ispitivanog čelika sa zadovoljavajućom točnošću mogu procjenjivati već i samo na osnovi njegove tvrdoće

Alignment of cellular motility forces with tissue flow as a mechanism for efficient wound healing

Recent experiments have shown that spreading epithelial sheets exhibit a long-range coordination of motility forces that leads to a buildup of tension in the tissue, which may enhance cell division and the speed of wound healing. Furthermore, the edges of these epithelial sheets commonly show finger-like protrusions whereas the bulk often displays spontaneous swirls of motile cells. To explain these experimental observations, we propose a simple flocking-type mechanism, in which cells tend to align their motility forceswith their velocity. Implementing this idea in amechanical tissue simulation, the proposed model gives rise to efficient spreading and can explain the experimentally observed long-range alignment of motility forces in highly disordered patterns, as well as the buildup of tensile stress throughout the tissue. Our model also qualitatively reproduces the dependence of swirl size and swirl velocity on cell density reported in experiments and exhibits an undulation instability at the edge of the spreading tissue commonly observed in vivo. Finally, we study the dependence of colony spreading speed on important physical and biological parameters and derive simple scaling relations that show that coordination of motility forces leads to an improvement of the wound healing process for realistic tissue parameters

Security methods for a group of mobile robots according to the requirements of Russian and foreign legislation

This paper is devoted to the problem of creating security methods for mobile robotic systems. The urgency of the problem of ensuring the security of mobile robotic systems is associated with the presence of a contradiction between the growing popularity of the mobile robotic systems and the presence of many vulnerabilitie

Hydrography in the Mediterranean Sea during a cruise with RV Poseidon in April 2014

We report on data from an oceanographic cruise in the Mediterranean Sea on the German research vessel Poseidon in April 2014. Data were taken on a west–east section, starting at the Strait of Gibraltar and ending south-east of Crete, as well on sections in the Ionian and Adriatic Sea. The objectives of the cruise were threefold: to contribute to the investigation of the spatial evolution of the Levantine Intermediate Water (LIW) properties and of the deep water masses in the eastern Mediterranean Sea, and to investigate the mesoscale variability of the upper water column. The measurements include salinity, temperature, oxygen and currents and were conducted with a conductivity, temperature and depth(CTD)/rosette system, an underway CTD and an acoustic Doppler current profiler (ADCP). The sections are on tracks which have been sampled during several other cruises, thus supporting the opportunity to investigate the long-term temporal development of the different variables. The use of an underway CTD made it possible to conduct measurements of temperature and salinity with a high horizontal spacing of 6 nm between stations and a vertical spacing of 1 dbar for the upper 800 m of the water column

Homeostatic competition drives tumor growth and metastasis nucleation

We propose a mechanism for tumor growth emphasizing the role of homeostatic regulation and tissue stability. We show that competition between surface and bulk effects leads to the existence of a critical size that must be overcome by metastases to reach macroscopic sizes. This property can qualitatively explain the observed size distributions of metastases, while size-independent growth rates cannot account for clinical and experimental data. In addition, it potentially explains the observed preferential growth of metastases on tissue surfaces and membranes such as the pleural and peritoneal layers, suggests a mechanism underlying the seed and soil hypothesis introduced by Stephen Paget in 1889 and yields realistic values for metastatic inefficiency. We propose a number of key experiments to test these concepts. The homeostatic pressure as introduced in this work could constitute a quantitative, experimentally accessible measure for the metastatic potential of early malignant growths.Comment: 13 pages, 11 figures, to be published in the HFSP Journa

Colloquium: Mechanical formalisms for tissue dynamics

The understanding of morphogenesis in living organisms has been renewed by tremendous progressin experimental techniques that provide access to cell-scale, quantitative information both on theshapes of cells within tissues and on the genes being expressed. This information suggests that ourunderstanding of the respective contributions of gene expression and mechanics, and of their crucialentanglement, will soon leap forward. Biomechanics increasingly benefits from models, which assistthe design and interpretation of experiments, point out the main ingredients and assumptions, andultimately lead to predictions. The newly accessible local information thus calls for a reflectionon how to select suitable classes of mechanical models. We review both mechanical ingredientssuggested by the current knowledge of tissue behaviour, and modelling methods that can helpgenerate a rheological diagram or a constitutive equation. We distinguish cell scale ("intra-cell")and tissue scale ("inter-cell") contributions. We recall the mathematical framework developpedfor continuum materials and explain how to transform a constitutive equation into a set of partialdifferential equations amenable to numerical resolution. We show that when plastic behaviour isrelevant, the dissipation function formalism appears appropriate to generate constitutive equations;its variational nature facilitates numerical implementation, and we discuss adaptations needed in thecase of large deformations. The present article gathers theoretical methods that can readily enhancethe significance of the data to be extracted from recent or future high throughput biomechanicalexperiments.Comment: 33 pages, 20 figures. This version (26 Sept. 2015) contains a few corrections to the published version, all in Appendix D.2 devoted to large deformation

Socio-economic impact of Foot-and-Mouth Disease outbreaks and control measures:An analysis of Mongolian outbreaks in 2017

Mongolia is a large landlocked country in central Asia and has one of the highest per capita livestock ratios in the world. During 2017 reported Foot and Mouth disease (FMD) outbreaks in Mongolia increased considerably, prompting widespread disease control measures. This study estimates the socio‐economic impact of FMD and subsequent control measures on Mongolian herders. The analysis encompassed quantification of the impact on subsistence farmers’ livelihoods and food security and estimation of the national level gross losses due to reaction and expenditure during 2017. Data were collected from 112 herders across eight Provinces that reported disease. Seventy of these herders had cases of FMD, while 42 did not have FMD in their animals but were within quarantine zones. Overall, 86/112 herders reported not drinking milk for a period of time and 38/112 reduced their meat consumption. Furthermore, 55 herders (49.1%) had to borrow money to buy food, medicines and/or pay bills or bank loans. Among herders with FMD cases, the median attack rate was 31.7%, 3.8% and 0.59% in cattle, sheep and goats respectively, with important differences across Provinces. Herders with clinical cases before the winter had higher odds of reporting a reduction in their meat consumption. National level gross losses due to FMD in 2017 were estimated using government data. The estimate of gross economic loss was 18.4 billion Mongolian‐tugriks (US$7.35 million) which equates to approximately 0.65% of the Mongolian GDP. The FMD outbreaks combined with current control measures has negatively impacted herders’ livelihoods (including herders with and without cases of FMD) which is likely to reduce stakeholder advocacy. Possible strategies that could be employed to ameliorate the negative effects of the current control policy were identified. The findings and approach are relevant to other FMD endemic regions aiming to control the disease

Developing models of IoT infrastructures to identify vulnerabilities and analyse threats

This article describes the developing stands of typical IoT infrastructure Technologies, which are designed to identify vulnerabilities and analyse potential threats. Scenarios of attacks typical for such systems have been developed, and the consequences of implementing attacks have been determined. Attacker can use the developed scenarios, been motivated by different goal