Molecular communication (MC) is a method where the transmission of information involves the use of molecules rather than electromagnetic (EM) waves. In this paper an open-air transmission MC experiment is conducted to study signal behavior and the noise. A mass spectrometer is used as the detector and an in-house-built odor generator is used as transmitter. It is shown that the signal amplitude loss of the signal can be modelled by using advection-diffusion with decay equation. In addition, the noise of the system has shown to have similar characteristics to that of additive white Gaussian noise (AWGN).

Molecular communication (MC) is an emerging field where the transmission of information occurs using particles (i.e., molecules, pheromones) instead of electromagnetic (EM) waves. This change in propagation medium opens up new possibilities for MC in areas where EM is inefficient or impossible such as underwater and underground communications. This study reports transmission experiments conducted to analyze the propagation behaviour in a closed boundary. It is shown that the behaviour can be explained by using the advection-diffusion equation (ADE) where the diffusion parameter of the equation plays a pivotal role in the process of the propagation. The signal properties of the transmission are analyzed and modelled theoretically and it is shown that the communication exhibits complex behaviour for signal amplitude, signal energy and signal-to-noise ratio with respect to transmission distance.

To date, the commonly used methods to assess rumen fermentation are invasive. Exhaled breath contains hundreds of volatile organic compounds (VOC) that can reflect animal physiological processes. In the present study, for the first time, we aimed to use a non-invasive metabolomics approach based on high-resolution mass spectrometry to identify rumen fermentation parameters in dairy cows. Enteric methane (CH₄) production from 7 lactating cows was measured 8 times over 2 consecutive days using the GreenFeed system. Simultaneously, exhalome samples were collected in Tedlar gas sampling bags and analyzed offline using a secondary electrospray ionization high-resolution mass spectrometry (SESI-HRMS) system. In total, 1,298 features were detected, among them targeted exhaled volatile fatty acids (eVFA, i.e., acetate, propionate, butyrate), which were putatively annotated using their exact mass-to-charge ratio. The intensity of eVFA, in particular acetate, increased immediately after feeding and followed a similar pattern observed for ruminal CH₄ production. The average total eVFA concentration was 35.4 count-per-second (CPS), and among the individual eVFA, acetate had the greatest concentration, averaging 21.0 CPS followed by propionate at 11.5 CPS, and butyrate at 2.82 CPS. Further, exhaled acetate was on average the most abundant of the individual eVFA at around 59.3%, followed by 32.5 and 7.9% of the total eVFA for propionate and butyrate, respectively. This corresponds well with the previously reported proportions of these VFA in the rumen. The diurnal patterns of ruminal CH₄ emission and individual eVFA were characterized using a linear mixed model with cosine function fit. The model characterized similar diurnal patterns for eVFA and ruminal CH₄ and H₂ production. Regarding the diurnal patterns of eVFA, the phase (time of peak) of butyrate occurred first, followed by that of acetate and propionate. Importantly, the phase of total eVFA occurred around 1 h before that of ruminal CH₄. This corresponds well with existing data on the relationship between rumen VFA production and CH₄ formation. Results from the present study revealed a great potential to assess the rumen fermentation of dairy cows using exhaled metabolites as a non-invasive proxy for rumen VFA. Further validation, with comparisons to rumen fluid, and establishment of the proposed method are required.

Development and testing of a dynamic vapor generator for the qualitative and quantitative analysis of volatile short-chain fatty acids in the gas phase using a secondary electrospray ionization source coupled to a high-resolution mass spectrometer.