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We consider a decentralized wireless network with several source-destination pairs sharing a limited number of orthogonal frequency bands. Sources learn to adapt their transmissions (specifically, their band selection strategy) over time, in a decentralized manner, without sharing information with each other. Sources can only observe the outcome of their own transmissions (i.e., success or collision), having no prior knowledge of the network size or of the transmission strategy of other sources. The goal of each source is to maximize their own throughput while striving for network-wide fairness. We propose a novel fully decentralized Reinforcement Learning (RL)-based solution that achieves fairness without coordination. The proposed Fair Share RL (FSRL) solution combines: (i) state augmentation with a semi-adaptive time reference; (ii) an architecture that leverages risk control and time difference likelihood; and (iii) a fairnessdriven reward structure. We evaluate FSRL in several network settings. Simulation results suggest that, when we compare FSRL with a common baseline RL algorithm from the literature, FSRL can be up to 89.0% fairer (as measured by Jain’s fairness index) in stringent settings with several sources and a single frequency band, and 48.1% fairer on average. 

Chirality effects on the intrinsic gas-phase acidity of oligopeptides have been studied using a pair of stereoisomeric tripeptides consisting of a D/L-cysteine (C) and two residues of alanine (A): CAA and dCAA, where the C-terminus is amidated. Mass spectrometry measurements through bracketing via collision-induced dissociation clearly show that CAA is a stronger gas-phase acid than dCAA. Quantitative values of the acidity were determined using the extended Cooks kinetic method. The resulting deprotonation enthalpy (∆acidH) for CAA is 326.2 kcal/mol (1364.7 kJ/mol) and for dCAA it is 326.8 kcal/mol (1367.6 kJ/mol). The corresponding gas-phase acidity (∆acidG) for CAA is 321.3 kcal/mol (1344.2 kJ/mol) and for dCAA it is 322.0 kcal/mol (1347.3 kJ/mol). Changing the N-terminal cysteine from the L-form to the D-form reduces the gas-phase acidity by about 0.6 kcal/mol (2.5 kJ/mol). Extensive conformational searches followed by quantum chemical calculations at the ωB97X-D/6-311+G(d,p) level of theory yielded a set of lowest energy conformations for each peptide species. Theoretical gas-phase acidities calculated using the Boltzmann averaged conformational contributions are in good agreement with the experimental data. The shift in the acidity is likely due to the conformational effect induced by D-cysteine, which increases the stability of the neutral dCAA, and hence reduces its acidity. A chirality change on a single amino acid can have a noticeable effect on the biochemical properties of peptides and proteins.