The study in [22] proposed a reservation-based MAC protocol, T-Lohi, where a node sends a short tone to count the number of contenders. If it does not receive any other tones, it starts data transmission. Otherwise, it goes to the backoff mode.Although our work is also based on channel contention, those studies differ from ours since they do not consider the provision of QoS or optimality.There are few MAC protocols that address QoS provision in UASNs. However, there have been several MAC protocols that considered QoS provision for wireless sensor networks [32�C39].In particular, the authors of [37] proposed I-MAC, a hybrid TDMA/CSMA-based MAC protocol for wireless sensor networks. The I-MAC protocol is composed of two phases: the setup and transmission phases.
During the setup phase, neighbor node discovery, slot assignment, local framing and global synchronization operations are successively performed. If a node owns assigned slots, it transmits data using those slots. If a node does not own any slot, it uses CSMA to access the channel. By using a different value of the CW (contention window), some groups of nodes can have a higher priority for accessing the channel.As another e
Iron is an important metal ion since it is essential in many metabolic pathways. However, the concentration of Fe(III) in biological systems has to be efficiently balanced as both its deficiency and excess can cause various biological disorders [1]. The same holds for environmental systems, such as fresh and seawaters, in which the iron concentration is claimed to be of crucial relevance [2].
Thus new methods for iron analysis are widely required, in particular for in situ applications, i.e., not only sensitive, but also robust, rapid, easy to perform and possibly at low cost. Sensor technology is particularly suited to meeting these aims.Deferoxamine B (DFO), a bacterial hydroxamate siderophore, has a high affinity for Fe(III), so that DFO is one of the most employed drugs used in chelation therapy to remove excess iron from blood and tissues [3,4]. In particular, DFO forms 1:1 Fe-DFO octahedral complex involving the six oxygen atoms of the hydroxamate groups [5]. The terminal amino group is not involved in iron complexation, therefore it is available for anchoring DFO onto a solid phase.
On the basis of this strategy, we have previously developed and reported a sensor for Fe(III) based on spectrophotometric GSK-3 transduction called DFO Self-Assembled Monolayers on Mesoporous Silica (DFO SAMMS) [6].In this work, we present a sensor for Fe(III) with optical transduction based on the surface plasmon resonance phenomenon excited at the interface of a dielectric layer and a gold film, exploiting a multimode Plastic Optical Fiber (POF) as the light guiding structure (see Figure 1). DFO has been anchored to the gold surface as a self-assembled monolayer (SAM) affording a DFO-SAM-modified interface [7].