Evaluation of PPG Biometrics for Authentication in different states

Amongst all medical biometric traits, Photoplethysmograph (PPG) is the easiest to acquire. PPG records the blood volume change with just combination of Light Emitting Diode and Photodiode from any part of the body. With IoT and smart homes' penetration, PPG recording can easily be integrated with other vital wearable devices. PPG represents peculiarity of hemodynamics and cardiovascular system for each individual. This paper presents non-fiducial method for PPG based biometric authentication. Being a physiological signal, PPG signal alters with physical/mental stress and time. For robustness, these variations cannot be ignored. While, most of the previous works focused only on single session, this paper demonstrates extensive performance evaluation of PPG biometrics against single session data, different emotions, physical exercise and time-lapse using Continuous Wavelet Transform (CWT) and Direct Linear Discriminant Analysis (DLDA). When evaluated on different states and datasets, equal error rate (EER) of $0.5\%$-$6\%$ was achieved for $45$-$60$s average training time. Our CWT/DLDA based technique outperformed all other dimensionality reduction techniques and previous work.Comment: Accepted at 11th IAPR/IEEE International Conference on Biometrics, 2018. 6 pages, 6 figure

A Comparative Study of Pedicled Versus Skeletonized Left Internal Mammary Artery Harvesting Techniques Regarding Rate of Mediastinitis Post CABG in Diabetic Patients

Background: For grafting the left anterior descending (LAD) coronary artery, the left internal mammary artery (LIMA) has become the gold standard. Pedicled and skeletonized methods are the two most common harvesting procedures. Objective: In this study we compared between both techniques regarding incidence of postoperative mediastinitis in diabetic patients. Patients and methods: 80 diabetic patients with controlled diabetes i.e. HbA1c below 7 underwent on-pump coronary artery bypass grafting (CABG) surgery were included in this study. The patients were divided into two groups, according to the procedure applied to harvest the LIMA: Group 1: 40 patients underwent pedicled LIMA and Group 2: 40 patients underwent skeletonized LIMA. After CABG surgery, the cases had a 3-month follow-up time. Results: In the pedicled LIMA group, the frequency of excessive intraoperative usage of bone wax was significantly increased. A significant increase was found regarding the occurrence of sternal wound infections (SWI) in the pedicled LIMA group (22.5%) versus (12.5%) within the skeletonized one, (P-value = 0.003). The univariate analysis of the factors related to SWI in all of the studied CABG patients were obesity [OR (95% CI): 15.61 (5.78-42.12), P <0.001], pedicled ITA [OR (95% CI): 4.3(1.4-12.9), P 0.004], intraoperative excessive use of bone wax [OR (95% CI): 14.53(6.48-32.56), P <0.001], and intraoperative excessive use of diathermy [OR (95% CI): 17.31(7.55-39.4), P <0.001]. Conclusion: In comparison to pedicled LIMA, skeletonized LIMA in CABG was correlated to reduced occurrence of superficial as well as deep SWI among diabetic patients

Existence of gradient CKV and gradient conformally stationary LRS spacetimes

In this work, we study the existence of gradient CKVs in locally rotationally symmetric spacetimes, those CKVs in the subspace spanned by the tangent to observers' congruence and that of the preferred spatial direction, allowing us to provide a (partial) characterization of gradient conformally static (GCSt) LRS solutions. Irrrotational solutions with non-zero spatial twist admit an irrotational timelike gradient conformal Killing vector field and hence are GCSt. In the case that both the vorticity and twist vanish, we obtain the necessary and sufficient condition for the spacetime to admit a gradient CKV. This is given by a single wave-like PDE, whose solutions are in bijection to the gradient CKVs on the spacetime. We then introduce a characterization of these spacetimes as GCSt using the character of the divergence of the CKV, provided that the metric functions of the spacetimes obey certain inequalities.Comment: 13 pages, no figure, Major modifications: The title has been changed in accordance with the modified content of the paper; Updated presentation of results; Some new results of characterization of gradient conformally stationary LRS spacetimes; all comments/suggestions are welcom

Horizon area bound and MOTS stability in locally rotationally symmetric solutions

In this paper, we study the stability of marginally outer trapped surfaces (MOTS), foliating horizons of the form $r=X(\tau)$, embedded in locally rotationally symmetric class II perfect fluid spacetimes. An upper bound on the area of stable MOTS is obtained. It is shown that any stable MOTS of the types considered in these spacetimes must be strictly stably outermost, that is, there are no MOTS ``outside" of and homologous to $\mathcal{S}$. Aspects of the topology of the MOTS, as well as the case when an extension is made to imperfect fluids, are discussed. Some non-existence results are also obtained. Finally, the ``growth" of certain matter and curvature quantities on certain unstable MOTS are provided under specified conditions.Comment: 21 pages, Submitted to CQG, comments are welcom