Block-Wise Two-Dimensional Maximum Margin Criterion for Face Recognition

Maximum margin criterion (MMC) is a well-known method for feature extraction and dimensionality reduction. However, MMC is based on vector data and fails to exploit local characteristics of image data. In this paper, we propose a two-dimensional generalized framework based on a block-wise approach for MMC, to deal with matrix representation data, that is, images. The proposed method, namely, block-wise two-dimensional maximum margin criterion (B2D-MMC), aims to find local subspace projections using unilateral matrix multiplication in each block set, such that in the subspace a block is close to those belonging to the same class but far from those belonging to different classes. B2D-MMC avoids iterations and alternations as in current bilateral projection based two-dimensional feature extraction techniques by seeking a closed form solution of one-side projection matrix for each block set. Theoretical analysis and experiments on benchmark face databases illustrate that the proposed method is effective and efficient.

Expression patterns of nociceptin in rats following experimental tooth movement

ABSTRACT Objectives: To determine the expression levels of nociceptin following experimental tooth movement. Materials and Methods: A total of 72 male Sprague-Dawley rats were divided into two groups: sham and experimental groups. For the experimental group, closed coil springs were used to mimic orthodontic force (80 g) between upper incisors and first molars, and the rats were killed at 0 hours, 4 hours, 12 hours, 1 day, 2 days, 5 days, 7 days, 10 days, and 14 days. All of these procedures were similar for the sham group, except for that no force was applied. The four rats killed at 0 hours without any intervention were used as the baseline control in each group. Trigeminal nucleus caudalis from both the ipsilateral and contralateral sides of force applications were obtained for immunostaining. Results: Nociceptin was expressed in both the ipsilateral and contralateral sides of each group. Its expression levels started to increase on day 2, peaked on day 7, and returned to baseline on day 10 in the experimental group, while expression levels started to decrease on day 1 and returned to baseline on day 10 in the sham group. Moreover, the expression levels were similar between the ipsilateral and contralateral sides in each group. Conclusion: The expression levels of nociceptin were elevated following experimental tooth movement. The anesthetic agent used in this study (chloral hydrate) may have an antagonism with nociceptin. Due to bilateral innervation of anterior teeth and bilateral projection of nerve fibers, the expression levels of nociceptin were similar between ipsilateral and contralateral sides.