HBS: a novel biometric feature based on heartbeat morphology

In this paper, a new feature named heartbeat shape (HBS) is proposed for ECG-based biometrics. HBS is computed from the morphology of segmented heartbeats. Computation of the feature involves three basic steps: 1) resampling and normalization of a heartbeat; 2) reduction of matching error; and 3) shift invariant transformation. In order to construct both gallery and probe templates, a few consecutive heartbeats which could be captured in a reasonably short period of time are required. Thus, the identification and verification methods become efficient. We have tested the proposed feature independently on two publicly available databases with 76 and 26 subjects, respectively, for identification and verification. The second database contains several subjects having clinically proven cardiac irregularities (atrial premature contraction arrhythmia). Experiments on these two databases yielded high identification accuracy (98% and 99.85%, respectively) and low verification equal error rate (1.88% and 0.38%, respectively). These results were obtained by using templates constructed from five consecutive heartbeats only. This feature compresses the original ECG signal significantly to be useful for efficient communication and access of information in telecardiology scenarios.     

Partial isometries: Factorization and connected components

In this paper we compute the distance between the connected components of the sets of all partial isometries and essential partial isometries. Some factorization results are also proved. This complements previous results due to P.R. Halmos and J.E. McLaughlin     

Atom interferometry as a detector of rotation and gravitational waves: comparison of various diffraction processes

In this paper, we discuss the optimization of atom interferometers for rotation and gravitational wave detection. We consider various diffraction processes and we focus our analysis on Bragg diffraction by a laser standing wave. We show that high order diffraction should be feasible with moderate laser power.