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J Kittler

Publications and source records attributed to J Kittler.

4 recordsLinked to original sources
PubMed2005

Feature-based affine-Invariant localization of faces.

We present a novel method for localizing faces in person identification scenarios. Such scenarios involve high resolution images of frontal faces. The proposed algorithm does not require color, copes well in cluttered backgrounds, and accurately localizes faces including eye centers. An extensive analysis and a performance evaluation on the XM2VTS database and on the realistic BioID and BANCA face databases is presented. We show that the algorithm has precision superior to reference methods.

Algorithms↗
PubMed2005

Locally linear discriminant analysis for multimodally distributed classes for face recognition with a single model image.

We present a novel method of nonlinear discriminant analysis involving a set of locally linear transformations called "Locally Linear Discriminant Analysis (LLDA)." The underlying idea is that global nonlinear data structures are locally linear and local structures can be linearly aligned. Input vectors are projected into each local feature space by linear transformations found to yield locally linearly transformed classes that maximize the between-class covariance while minimizing the within-class covariance. In face recognition, linear discriminant analysis (LDA) has been widely adopted owing to its efficiency, but it does not capture nonlinear manifolds of faces which exhibit pose variations. Conventional nonlinear classification methods based on kernels such as generalized discriminant analysis (GDA) and support vector machine (SVM) have been developed to overcome the shortcomings of the linear method, but they have the drawback of high computational cost of classification and overfitting. Our method is for multiclass nonlinear discrimination and it is computationally highly efficient as compared to GDA. The method does not suffer from overfitting by virtue of the linear base structure of the solution. A novel gradient-based learning algorithm is proposed for finding the optimal set of local linear bases. The optimization does not exhibit a local-maxima problem. The transformation functions facilitate robust face recognition in a low-dimensional subspace, under pose variations, using a single model image. The classification results are given for both synthetic and real face data.

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PubMed1998

Effects of long-term exposure to delta9-THC on expression of cannabinoid receptor (CB1) mRNA in different rat brain regions.

The time course of changes across 21 days of continuous exposure to Delta9-tetrahydrocannabinol (Delta9-THC) was assessed for the level of cannabinoid receptor (CB1) mRNA expression in three different rat brain regions: cerebellum, hippocampus and corpus striatum. Expression levels of CB1 mRNA were determined using semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) following a protocol which included a gene standard, 28S ribonucleic acid protein (rRNA), for normalization of levels of RNA in the three different brain regions. The levels of CB1 mRNA were assessed in four different rats at each of seven time points (6 h, and 1, 2, 3, 7, 14 and 21 days) during a 21-day Delta9-THC one dose day-1 (10 mg kg-1) treatment regimen. In the cerebellum and hippocampus, CB1 mRNA levels were increased above vehicle control animals at 7 and 14 days of treatment. In the striatum the levels of CB1 transcripts were severely reduced from days 2-14. CB1 message expression in all three brain areas returned to vehicle control levels by day 21 of Delta9-THC treatment, a time at which behavioral tolerance has been previously reported. An additional measure, receptor stimulated GTPgammaS binding, performed over the same time period revealed differential desensitization within the 3 brain areas as a function of chronic exposure to Delta9-THC. Hippocampus was the earliest to desensitize decreasing to 35% of control by treatment day 7, followed by a decrease in the cerebellum to that same level on day 14 of treatment. The striatum showed only half that degree of desensitization (65%) over the entire 21-day treatment period. Comparisons suggests that CB1 message may be regulated by different effector systems in each of the three areas during chronic Delta9-THC exposure.

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