Robotic Wireless Sensor Networks

In this chapter, we present a literature survey of an emerging, cutting-edge, and multi-disciplinary field of research at the intersection of Robotics and Wireless Sensor Networks (WSN) which we refer to as Robotic Wireless Sensor Networks (RWSN). We define a RWSN as an autonomous networked multi-robot system that aims to achieve certain sensing goals while meeting and maintaining certain communication performance requirements, through cooperative control, learning and adaptation. While both of the component areas, i.e., Robotics and WSN, are very well-known and well-explored, there exist a whole set of new opportunities and research directions at the intersection of these two fields which are relatively or even completely unexplored. One such example would be the use of a set of robotic routers to set up a temporary communication path between a sender and a receiver that uses the controlled mobility to the advantage of packet routing. We find that there exist only a limited number of articles to be directly categorized as RWSN related works whereas there exist a range of articles in the robotics and the WSN literature that are also relevant to this new field of research. To connect the dots, we first identify the core problems and research trends related to RWSN such as connectivity, localization, routing, and robust flow of information. Next, we classify the existing research on RWSN as well as the relevant state-of-the-arts from robotics and WSN community according to the problems and trends identified in the first step. Lastly, we analyze what is missing in the existing literature, and identify topics that require more research attention in the future

Investigations of Vibrational Coherence in the Low-Frequency Region of Ferric Heme Proteins

Femtosecond coherence spectroscopy is applied to a series of ferric heme protein samples. The low-frequency vibrational spectra that are revealed show dominant oscillations near 40 cm−1. MbCN is taken as a typical example of a histidine-ligated, six-coordinate, ferric heme and a comprehensive spectroscopic analysis is carried out. The results of this analysis reveal a new heme photoproduct species, absorbing near 418 nm, which is consistent with the photolysis of the His93 axial ligand. The photoproduct undergoes subsequent rebinding/recovery with a time constant of ∼4 ps. The photoproduct lineshapes are consistent with a photolysis quantum yield of 75–100%, although the observation of a relatively strong six-coordinate heme coherence near 252 cm−1 (assigned to ν9 in the MbCN Raman spectrum) suggests that the 75% lower limit is much more likely. The phase and amplitude excitation profiles of the low-frequency mode at 40 cm−1 suggest that this mode is strongly coupled to the MbCN photoproduct species and it is assigned to the doming mode of the transient penta-coordinated material. The absolute phase of the 40 cm−1 mode is found to be π/2 on the red side of 418 nm and it jumps to 3π/2 as excitation is tuned to the blue side of 418 nm. The absolute phase of the 40 cm−1 signal is not explained by the standard theory for resonant impulsive stimulated Raman scattering. New mechanisms that give a dominant momentum impulse to the resonant wavepacket, rather than a coordinate displacement, are discussed. The possibilities of heme iron atom recoil after photolysis, as well as ultrafast nonradiative decay, are explored as potential ways to generate the strong momentum impulse needed to understand the phase properties of the 40 cm−1 mode