Modeling duct flow for molecular communication

Active transport such as fluid flow is sought in molecular communication to extend coverage, improve reliability, and mitigate interference. Flow models are often over-simplified, assuming one-dimensional diffusion with constant drift. However, diffusion and flow are usually encountered in three-dimensional bounded environments where the flow is highly non-uniform such as in blood vessels or microfluidic channels. For a qualitative understanding of the relevant physical effects inherent to these channels, based on the Peclet number and the transmitter-receiver distance, we study when simplified models of uniform flow and advection-only transport are applicable. For these two regimes, analytical expressions for the channel impulse response are derived and validated by particle-based simulation. Furthermore, as advection-only transport is typically overlooked and hence not analyzed in the molecular communication literature, we evaluate the symbol error rate for exemplary on-off keying as performance metric

Channel modeling for diffusive molecular communication - a tutorial review

Molecular communication (MC) is a new communication engineering paradigm where molecules are employed as information carriers. MC systems are expected to enable new revolutionary applications such as sensing of target substances in biotechnology, smart drug delivery in medicine, and monitoring of oil pipelines or chemical reactors in industrial settings. As for any other kind of communication, simple yet sufficiently accurate channel models are needed for the design, analysis, and efficient operation of MC systems. In this paper, we provide a tutorial review on mathematical channel modeling for diffusive MC systems. The considered end-to-end MC channel models incorporate the effects of the release mechanism, the MC environment, and the reception mechanism on the observed information molecules. Thereby, the various existing models for the different components of an MC system are presented under a common framework and the underlying biological, chemical, and physical phenomena are discussed. Deterministic models characterizing the expected number of molecules observed at the receiver and statistical models characterizing the actual number of observed molecules are developed. In addition, we provide channel models for timevarying MC systems with moving transmitters and receivers, which are relevant for advanced applications such as smart drug delivery with mobile nanomachines. For complex scenarios, where simple MC channel models cannot be obtained from first principles, we investigate simulation-driven and experiment-driven channel models. Finally, we provide a detailed discussion of potential challenges, open research problems, and future directions in channel modeling for diffusive MC systems

RANS Equations with Explicit Data-Driven Reynolds Stress Closure Can Be Ill-Conditioned

Reynolds-averaged Navier--Stokes (RANS) simulations with turbulence closure models continue to play important roles in industrial flow simulations. However, the commonly used linear eddy viscosity models are intrinsically unable to handle flows with non-equilibrium turbulence. Reynolds stress models, on the other hand, are plagued by their lack of robustness. Recent studies in plane channel flows found that even substituting Reynolds stresses with errors below 0.5% from direct numerical simulation (DNS) databases into RANS equations leads to velocities with large errors (up to 35%). While such an observation may have only marginal relevance to traditional Reynolds stress models, it is disturbing for the recently emerging data-driven models that treat the Reynolds stress as an explicit source term in the RANS equations, as it suggests that the RANS equations with such models can be ill-conditioned. So far, a rigorous analysis of the condition of such models is still lacking. As such, in this work we propose a metric based on local condition number function for a priori evaluation of the conditioning of the RANS equations. We further show that the ill-conditioning cannot be explained by the global matrix condition number of the discretized RANS equations. Comprehensive numerical tests are performed on turbulent channel flows at various Reynolds numbers and additionally on two complex flows, i.e., flow over periodic hills and flow in a square duct. Results suggest that the proposed metric can adequately explain observations in previous studies, i.e., deteriorated model conditioning with increasing Reynolds number and better conditioning of the implicit treatment of Reynolds stress compared to the explicit treatment. This metric can play critical roles in the future development of data-driven turbulence models by enforcing the conditioning as a requirement on these models.Comment: 35 pages, 18 figure

Channel Modeling for Diffusive Molecular Communication - A Tutorial Review

Molecular communication (MC) is a new communication engineering paradigm where molecules are employed as information carriers. MC systems are expected to enable new revolutionary applications such as sensing of target substances in biotechnology, smart drug delivery in medicine, and monitoring of oil pipelines or chemical reactors in industrial settings. As for any other kind of communication, simple yet sufficiently accurate channel models are needed for the design, analysis, and efficient operation of MC systems. In this paper, we provide a tutorial review on mathematical channel modeling for diffusive MC systems. The considered end-to-end MC channel models incorporate the effects of the release mechanism, the MC environment, and the reception mechanism on the observed information molecules. Thereby, the various existing models for the different components of an MC system are presented under a common framework and the underlying biological, chemical, and physical phenomena are discussed. Deterministic models characterizing the expected number of molecules observed at the receiver and statistical models characterizing the actual number of observed molecules are developed. In addition, we provide channel models for time-varying MC systems with moving transmitters and receivers, which are relevant for advanced applications such as smart drug delivery with mobile nanomachines. For complex scenarios, where simple MC channel models cannot be obtained from first principles, we investigate simulation-driven and experimentally-driven channel models. Finally, we provide a detailed discussion of potential challenges, open research problems, and future directions in channel modeling for diffusive MC systems.Comment: 40 pages; 23 figures, 2 tables; this paper is submitted to the Proceedings of IEE

Medical Genetic Counseling Of Women With Congenital Heart Diseases Of Fetus

Aim of the work. Determine the effectiveness of prenatal diagnosis of congenital heart defects in the fetus and the informativeness of different markers used in the medical-genetic counseling of pregnant women..Materials and methods. The analysis of the results of medical genetic counseling of pregnant women with fetal heart diseases was carried out. The effectiveness of using different methods of prenatal diagnosis in 67 pregnant women is estimated. The data of somatic, genealogical and reproductive anamnesis, biochemical markers of chromosomal pathology of the 1st and 2nd trimester of pregnancy, and the spectrum of the detected fetal heart disease were studied.Results of the research. It was found that 46 (68.7 %) women had somatic diseases: pathology of the cardiovascular system (11.9 %); endocrine system - at 8 (11,9 %); respiratory disease – 3 (4.5 %) and urinary system – 2 (3.0 %). 13 (19.4 %) out of 67 women had acute respiratory viral infections in the first trimester of pregnancy. In 4 (6 %) cases - bad habits. The first time pregnant were 31 (46.3 %) women, 21 (31.3 %) – the second time, 10 (14.9 %) in the third, and 5 (7.5 %) in the fourth or more times. In history, 58 (86.6 %) women did not have reproductive function disorders, 8 (11.9 %) had unauthorized miscarriages and frozen pregnancy. The burden of gynecological anamnesis was observed in 12 (17.9 %) women, and hereditary - in 6 (9.0 %) women. In the structure of congenital defects of the heart, false anatomical anomalies were found more often: hypoplasia of the left heart organs – 14 (20.9 %), tetralogy of Fallot - 9 (13.3 %). Biochemical markers of chromosomal pathology in the first trimester in 11 (16.4 %) women recorded indicators that are characteristic of the risk of chromosomal pathology, and in the second trimester – in 9 (13.4 %). Two pregnant women used a NIPT (non-invasive prenatal test) test that did not detect chromosomal abnormalities in the fetus. In 8 cases, invasive prenatal diagnosis of the fetus was recommended, which was carried out by three women, and five refused.Conclusions. The peculiarities of somatic (in 46–68.7 % of women), reproductive (in 8-11.9 % of women) gynecological anamnesis (in 12–17.9 % of women), which can be the risk factors of congenital fetal heart disease, are revealed. In the structure of congenital defects of the heart of the fetus more often revealed hypoplasia of the left heart organs – 14 (20.9 %), tetralogy of Fallot – 9 (13.3 %). In 11 (16.4 %) women recorded indicators of biochemical markers, characteristic for the risk of chromosomal pathology, in the first trimester, and – in 9 (13.4 %) pregnant women – in the second trimester. Comparative data on prenatal diagnosis of congenital heart defects in the fetus of chromosomal, monogenic and multifactorial etiology are given. On the basis of the obtained results an algorithm of medical-genetic counseling of this contingent of patients was offered

Analytical Derivation of the Impulse Response for the Bounded 2-D Diffusion Channel

This paper focuses on the derivation of the distribution of diffused particles absorbed by an agent in a bounded environment. In particular, we analogously consider to derive the impulse response of a molecular communication channel in 2-D and 3-D environment. In 2-D, the channel involves a point transmitter that releases molecules to a circular absorbing receiver that absorbs incoming molecules in an environment surrounded by a circular reflecting boundary. Considering this setup, the joint distribution of the molecules on the circular absorbing receiver with respect to time and angle is derived. Using this distribution, the channel characteristics are examined. Furthermore, we also extend this channel model to 3-D using a cylindrical receiver and investigate the channel properties. We also propose how to obtain an analytical solution for the unbounded 2-D channel from our derived solutions, as no analytical derivation for this channel is present in the literature.Comment: 13 pages and 5 figure

Functional Relationships between Kinetic, Flow, and Geometrical Parameters in a High-Temperature Chemical Microreactor.

Computational fluid dynamics (CFD) simulations and isothermal approximation were applied for the interpretation of experimental measurements of the C10H7Br pyrolysis efficiency in the high-temperature microreactor and of the pressure drop in the flow tube of the reactor. Applying isothermal approximation allows the derivation of analytical relationships between the kinetic, gas flow, and geometrical parameters of the microreactor, which, along with CFD simulations, accurately predict the experimental observations. On the basis of the obtained analytical relationships, a clear strategy for measuring rate coefficients of (pseudo) first-order bimolecular and unimolecular reactions using the microreactor was proposed. The pressure- and temperature-dependent rate coefficients for the C10H7Br pyrolysis calculated using variable reaction coordinate transition state theory were invoked to interpret the experimental data on the pyrolysis efficiency