We describe experimental vignette methodology (EVM) as a way to address the dilemma of conducting experimental research that results in high levels of confidence regarding internal validity but is challenged by threats to external validity versus conducting nonexperimental research that usually maximizes external validity but whose conclusions are ambiguous regarding causal relationships. EVM studies consist of presenting participants with carefully constructed and realistic scenarios to assess dependent variables including intentions, attitudes, and behaviors, thereby enhancing experimental realism and also allowing researchers to manipulate and control independent variables. We describe two major types of EVM aimed at assessing explicit (i.e., paper people studies) and implicit (i.e., policy capturing and conjoint analysis) processes and outcomes. We offer best practice recommendations regarding the design and implementation of EVM studies based on a multidisciplinary literature review, discuss substant...

Best Practice Recommendations for Designing and Implementing Experimental Vignette Methodology Studies

With much advancement in the field of nanotechnology, bioengineering, and synthetic biology over the past decade, microscales and nanoscales devices are becoming a reality. Yet the problem of engineering a reliable communication system between tiny devices is still an open problem. At the same time, despite the prevalence of radio communication, there are still areas where traditional electromagnetic waves find it difficult or expensive to reach. Points of interest in industry, cities, and medical applications often lie in embedded and entrenched areas, accessible only by ventricles at scales too small for conventional radio waves and microwaves, or they are located in such a way that directional high frequency systems are ineffective. Inspired by nature, one solution to these problems is molecular communication (MC), where chemical signals are used to transfer information. Although biologists have studied MC for decades, it has only been researched for roughly 10 year from a communication engineering lens. Significant number of papers have been published to date, but owing to the need for interdisciplinary work, much of the results are preliminary. In this survey, the recent advancements in the field of MC engineering are highlighted. First, the biological, chemical, and physical processes used by an MC system are discussed. This includes different components of the MC transmitter and receiver, as well as the propagation and transport mechanisms. Then, a comprehensive survey of some of the recent works on MC through a communication engineering lens is provided. The survey ends with a technology readiness analysis of MC and future research directions.

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A Comprehensive Survey of Recent Advancements in Molecular Communication

Chemotactic bacteria are guided towards the source of a nutrient by local concentration gradients. That works on the microscopic scale, but at larger scales such local cues are unreliable pointers — for example, wind or water currents may disperse odours sought by foraging animals. Using statistical techniques, Vergassola et al. have developed a general search algorithm for movement strategies based on the detection of sporadic cues and partial information. The strategy, termed 'infotaxis' as it maximizes the expected rate of information gain, could find application in the design of 'sniffer' robots. A computational model of odour plume propagation and experimental data are used to devise a general search algorithm for movement strategies in chemotaxis, based on sporadic cues and partial information. The strategy is termed 'infotaxis' as it locally maximizes the expected rate of information gain. Chemotactic bacteria rely on local concentration gradients to guide them towards the source of a nutrient1. Such local cues pointing towards the location of the source are not always available at macroscopic scales because mixing in a flowing medium breaks up regions of high concentration into random and disconnected patches. Thus, animals sensing odours in air or water detect them only intermittently as patches sweep by on the wind or currents2,3,4,5,6. A macroscopic searcher must devise a strategy of movement based on sporadic cues and partial information. Here we propose a search algorithm, which we call ‘infotaxis’, designed to work under such conditions. Any search process can be thought of as acquisition of information on source location; for infotaxis, information plays a role similar to concentration in chemotaxis. The infotaxis strategy locally maximizes the expected rate of information gain. We demonstrate its efficiency using a computational model of odour plume propagation and experimental data on mixing flows7. Infotactic trajectories feature ‘zigzagging’ and ‘casting’ paths similar to those observed in the flight of moths8. The proposed search algorithm is relevant to the design of olfactory robots9,10,11, but the general idea of infotaxis can be applied more broadly in the context of searching with sparse information.

"Infotaxis" as a strategy for searching without gradients

A comprehensive review is presented on the development and state of the art of colorimetric and fluorometric sensor arrays. Optical arrays based on chemoresponsive colorants (dyes and nanoporous pigments) probe the chemical reactivity of analytes, rather than their physical properties. This provides a high dimensionality to chemical sensing that permits high sensitivity (often down to ppb levels), impressive discrimination among very similar analytes and exquisite fingerprinting of extremely similar mixtures over a wide range of analyte types, both in the gas and liquid phases.

https://zenodo.org/record/895426/files/article.pdf

Optical sensor arrays for chemical sensing: the optoelectronic nose

A comprehensive review on the development and state of the art of colorimetric and fluorometric sensor arrays is presented Chemical sensing aims to detect subtle changes in the chemical environment by transforming relevant chemical or physical properties of molecular or ionic species (ie, analytes) into an analytically useful output Optical arrays based on chemoresponsive colorants (dyes and nanoporous pigments) probe the chemical reactivity of analytes, rather than their physical properties (eg, mass) The chemical specificity of the olfactory system does not come from specific receptors for specific analytes (eg, the traditional lock-and-key model of substrate-enzyme interactions), but rather olfaction makes use of pattern recognition of the combined response of several hundred olfactory receptors In a similar fashion, arrays of chemoresponsive colorants provide high-dimensional data from the color or fluorescence changes of the dyes in these arrays as they are exposed to analytes This provides chemical sensing with high sensitivity (often down to parts per billion levels), impressive discrimination among very similar analytes, and exquisite fingerprinting of extremely similar mixtures over a wide range of analyte types, in both the gas and liquid phases Design of both sensor arrays and instrumentation for their analysis are discussed In addition, the various chemometric and statistical analyses of high-dimensional data (including hierarchical cluster analysis (HCA), principal component analysis (PCA), linear discriminant analysis (LDA), support vector machines (SVMs), and artificial neural networks (ANNs)) are presented and critiqued in reference to their use in chemical sensing A variety of applications are also discussed, including personal dosimetry of toxic industrial chemical, detection of explosives or accelerants, quality control of foods and beverages, biosensing intracellularly, identification of bacteria and fungi, and detection of cancer and disease biomarkers

The Optoelectronic Nose: Colorimetric and Fluorometric Sensor Arrays.

This paper reports on the development of compact surface plasmon resonance (SPR) sensors to be used for mobile robot olfaction. The proposed sensor uses a periodic metal structure formed on top of the self-assembled layer of polystyrene particles of 200 nm in diameter. With the grating of this size, SPR can be excited even with an LED light source. The change in the absorbance is simply measured using a photodiode. The experimental results are presented on a silver nanostructure sensor and a gold nanostructure sensor to show the potential of these sensors.

Compact SPR Gas Sensor for Mobile Robot Olfaction Using Metal Nanostructure and LED Light Source

This article describes the investigations on the effect of airflow on the perception of odors presented by an olfactory display device. A clear sensation of the direction to an odor source can be given to the user of the olfactory display when the air currents are provided to the user's face by using fans. When the air currents are not provided, the user feels as if the source is placed nearby. We hypothesize that this sensation is caused by the upward air currents generated by our body temperature. When there is no wind, only the odors from nearby sources are brought to our noses by the upward air currents. The result of a sensory test shows that the perceived location of an odor source changes with the airflow presented to the panelist. Providing airflow together with odors is thus promising to reproduce complicated situations that cannot be reproduced by olfactory stimulation alone.

On the effect of airflow on odor presentation

PROBLEM TO BE SOLVED: To enable a transmission system to transmit a packet at a transmission rate for enabling reception at a reception system even without receiving any confirm packet by transmitting a request data transfer rate to the transmission system at every prescribed timing after the reception of data and determining the transmission rate through the transmission system based on the received request data transfer rate. SOLUTION: When transmission data from an application 14 of a transmission system 10 are dispatched to a transport layer, a transmission buffer 11 divides these data into packets and performs queuing. The packet received from the low layer of a network 15 is queued in a reception buffer 21, the packet is extracted from the reception buffer 21 corresponding to the processing speed of an application 23, and it is dispatched to the application 23 as assembled data. The packet dispatched to the application 23 as data sends a confirm packet CP showing normal processing completion to the transmission system 10.

Data transfer system and transmission rate control method

PROBLEM TO BE SOLVED: To two-dimensionally and variably control a position of a smell source.SOLUTION: An air flow having a smell is collided with the other air flow to change a direction to the side of a user, a spatial distribution of a smell in which the source of the smell is present at a part where the air flow has collided is formed, the two air flows facing each other are collided, and the air flow having the smell and the other air flow are produced. Thus, the position of the smell source is two-dimensionally and variably changed.

Method and device for controlling spatial distribution of smell, audiovisual system and customer guide system

A new gas source localization method that uses actively generated airflow is proposed. A gas source localization robot searches for the location of a gas source by tracking a gas plume in the upwind direction. However, the robot often fails in tracking the plume in an actual environment owing to the large fluctuations of the airflow field and the plume structure. To overcome this problem, we propose to deploy in the environment a swarm of mobile robots equipped with fans to generate a stable airflow field so that a stable gas plume will be formed and the robot can easily track it. Experimental results are presented to show that the variations of the airflow field can be suppressed by the actively generated airflow even in an outdoor environment. It is also shown that errors in the gas source direction estimated by the robot can be reduced by the proposed method.

Hiroshi Ishida

Papers

Compact SPR Gas Sensor for Mobile Robot Olfaction Using Metal Nanostructure and LED Light Source

On the effect of airflow on odor presentation

Data transfer system and transmission rate control method

Method and device for controlling spatial distribution of smell, audiovisual system and customer guide system

Active Airflow Generation to Assist Robotic Gas Source Localization: Initial Experiments in Outdoor Environment