ABSTRACT
Kisspeptin neurons in the arcuate nucleus (ARC) regulate prolactin secretion, and are in physical contact with tuberoinfundibular dopaminergic (TIDA) neurons, which inhibit prolactin secretion. Prolactin levels in the blood are increased with advancing age in rats; therefore, we investigated the interactions with TIDA neurons and kisspeptin neurons in aged female rats (24 months of age), relative to those of young adult female rats (9-10 weeks of age). Plasma prolactin levels in the aged rats were significantly higher than those of young adult rats. Tyrosine hydroxylase (TH)-immunoreactive (ir) cell bodies and kisspeptin-ir nerve fibers were found in the dorsomedial ARC of both groups. The number of TH-ir cell bodies in the dorsomedial ARC did not differ significantly between groups. Additionally, no significant differences in the number of TH-ir cells in contact with kisspeptin-ir fibers was observed between groups. However, the number of kisspeptin-ir or Kiss1 mRNA-expressing cells in the ARC was significantly reduced in the aged rats compared with that of the young rats. These results suggest that the contacts between TIDA neurons and kisspeptin neurons are maintained after reproductive senescence, while production of kisspeptin in the ARC decreases significantly during aging.
ABSTRACT
We present an effective image boundary processing for M-channel (M ∈ IN, M ≥ 2) lifting-based linear-phase filter banks that are applied to unified lossy and lossless image compression (coding), i.e., lossy-to-lossless image coding. The reversible symmetric extension we propose is achieved by manipulating building blocks on the image boundary and reawakening the symmetry of each building block that has been lost due to rounding error on each lifting step. In addition, complexity is reduced by extending nonexpansive convolution, called reversible symmetric nonexpansive convolution, because the number of input signals does not even temporarily increase. Our method not only achieves reversible boundary processing, but also is comparable with irreversible symmetric extension in lossy image coding and outperformed periodic extension in lossy-to-lossless image coding.
ABSTRACT
Generalized block-lifting factorization of M-channel (M > 2) biorthogonal filter banks (BOFBs) for lossy-to-lossless image coding is presented in this paper. Since the proposed block-lifting structure is more general than the conventional lifting factorizations and does NOT require many restrictions such as paraunitary, number of channels, and McMillan degree in each building block unlike the conventional lifting factorizations, its coding gain is higher than that of the previous methods. Several proposed BOFBs are designed and applied to image coding. Comparing the results with conventional lossy-to-lossless image coding structures, including the 5/3- and 9/7-tap discrete wavelet transforms in JPEG 2000 and a 4 × 8 hierarchical lapped biorthogonal transform in JPEG XR, the proposed BOFBs achieve better result in both objective measure and perceptual visual quality for the images with a lot of high-frequency components.
ABSTRACT
A discrete cosine transform (DCT) can be easily implemented in software and hardware for the JPEG and MPEG formats. However, even though some integer DCTs (IntDCTs) for lossless-to-lossy image coding have been proposed, such transform requires redesigned devices. This paper proposes a hardware-friendly IntDCT that can be applied to both lossless and lossy coding. Our IntDCT is implemented by direct-lifting of DCT and inverse DCT (IDCT). Consequently, any existing DCT device can be directly applied to every lifting block. Although our method requires a small side information block (SIB), it is validated by its application to lossless-to-lossy image coding.
ABSTRACT
This paper proposes an efficient approach for adaptive directional wavelet transform (WT) based on directional prefiltering. Although the adaptive directional WT is able to transform an image along diagonal orientations as well as traditional horizontal and vertical directions, it sacrifices computation speed for good image coding performance. We present two efficient methods to find the best transform directions by prefiltering using 2-D filter bank or 1-D directional WT along two fixed directions. The proposed direction calculation methods achieve comparable image coding performance comparing to the conventional one with less complexity. Furthermore, transform direction data of the proposed method can be used for content-based image retrieval to increase retrieval ratio.
ABSTRACT
In this paper, effective multiresolution image representations using a combination of 2-D filter bank (FB) and directional wavelet transform (WT) are presented. The proposed methods yield simple implementation and low computation costs compared to previous 1-D and 2-D FB combinations or adaptive directional WT methods. Furthermore, they are nonredundant transforms and realize quad-tree like multiresolution representations. In applications on nonlinear approximation, image coding, and denoising, the proposed filter banks show visual quality improvements and have higher PSNR than the conventional separable WT or the contourlet.