Properties of a general quaternion-valued gradient operator and its applications to signal processing

The gradients of a quaternion-valued function are often required for quaternionic signal processing algorithms. The HR gradient operator provides a viable framework and has found a number of applications. However, the applications so far have been limited to mainly real-valued quaternion functions and linear quaternionvalued functions. To generalize the operator to nonlinear quaternion functions, we define a restricted version of the HR operator, which comes in two versions, the left and the right ones. We then present a detailed analysis of the properties of the operators, including several different product rules and chain rules. Using the new rules, we derive explicit expressions for the derivatives of a class of regular nonlinear quaternion-valued functions, and prove that the restricted HR gradients are consistent with the gradients in the real domain. As an application, the derivation of the least mean square algorithm and a nonlinear adaptive algorithm is provided. Simulation results based on vector sensor arrays are presented as an example to demonstrate the effectiveness of the quaternion-valued signal model and the derived signal processing algorithm

Filtering and Tracking with Trinion-Valued Adaptive Algorithms

A new model for three-dimensional processes based on the trinion algebra is introduced for the first time. Compared with the pure quaternion model, the trinion model is more compact and computationally more efficient, while having similar or comparable performance in terms of adaptive linear filtering. Moreover, the trinion model can effectively represent the general relationship of state evolution in Kalman filtering, where the pure quaternion model fails. Simulations on real-world wind recordings and synthetic data sets are provided to demonstrate the potentials of this new modeling method

Hepatitis C Virus Induces the Cannabinoid Receptor 1

BACKGROUND: Activation of hepatic CB(1) receptors (CB(1)) is associated with steatosis and fibrosis in experimental forms of liver disease. However, CB(1) expression has not been assessed in patients with chronic hepatitis C (CHC), a disease associated with insulin resistance, steatosis and metabolic disturbance. We aimed to determine the importance and explore the associations of CB(1) expression in CHC. METHODS: CB(1) receptor mRNA was measured by real time quantitative PCR on extracted liver tissue from 88 patients with CHC (genotypes 1 and 3), 12 controls and 10 patients with chronic hepatitis B (CHB). The Huh7/JFH1 Hepatitis C virus (HCV) cell culture model was used to validate results. PRINCIPAL FINDINGS: CB(1) was expressed in all patients with CHC and levels were 6-fold higher than in controls (P<0.001). CB(1) expression increased with fibrosis stage, with cirrhotics having up to a 2 fold up-regulation compared to those with low fibrosis stage (p<0.05). Even in mild CHC with no steatosis (F0-1), CB(1) levels remained substantially greater than in controls (p<0.001) and in those with mild CHB (F0-1; p<0.001). Huh7 cells infected with JFH-1 HCV showed an 8-fold upregulation of CB(1), and CB(1) expression directly correlated with the percentage of cells infected over time, suggesting that CB(1) is an HCV inducible gene. While HCV structural proteins appear essential for CB(1) induction, there was no core genotype specific difference in CB(1) expression. CB(1) significantly increased with steatosis grade, primarily driven by patients with genotype 3 CHC. In genotype 3 patients, CB(1) correlated with SREBP-1c and its downstream target FASN (SREBP-1c; R=0.37, FASN; R=0.39, p<0.05 for both). CONCLUSIONS/SIGNIFICANCE: CB(1) is up-regulated in CHC and is associated with increased steatosis in genotype 3. It is induced by the hepatitis C virus

Insulin-like growth factors and related proteins in plasma and cerebrospinal fluids of HIV-positive individuals

BACKGROUND: Clinically significant dysregulation of the insulin-like growth factor (IGF) family proteins occurs in HIV-infected individuals, but the details including whether the deficiencies in IGFs contribute to CNS dysfunction are unknown. METHODS: We measured the levels of IGF1, IGF2, IGFBP1, IGFBP2, and IGF2 receptor (IGF2R) in matching plasma and cerebrospinal fluid (CSF) samples of 107 HIV+ individuals from CNS HIV Antiretroviral Therapy Effects Research (CHARTER) and analyzed their associations with demographic and disease characteristics, as well as levels of several soluble inflammatory mediators (TNFα, IL-6, IL-10, IL-17, IP-10, MCP-1, and progranulin). We also determined whether IGF1 or IGF2 deficiency is associated with HIV-associated neurocognitive disorder (HAND) and whether the levels of soluble IGF2R (an IGF scavenging receptor, which we also have found to be a cofactor for HIV infection in vitro) correlate with HIV viral load (VL). RESULTS: There was a positive correlation between the levels of IGF-binding proteins (IGFBPs) and those of inflammatory mediators: between plasma IGFBP1 and IL-17 (β coefficient 0.28, P = 0.009), plasma IGFBP2 and IL-6 (β coefficient 0.209, P = 0.021), CSF IGFBP1 and TNFα (β coefficient 0.394, P < 0.001), and CSF IGFBP2 and TNF-α (β coefficient 0.14, P < 0.001). As IGFBPs limit IGF availability, these results suggest that inflammation is a significant factor that modulates IGF protein expression/availability in the setting of HIV infection. However, there was no significant association between HAND and the reduced levels of plasma IGF1, IGF2, or CSF IGF1, suggesting a limited power of our study. Interestingly, plasma IGF1 was significantly reduced in subjects on non-nucleoside reverse transcriptase inhibitor-based antiretroviral therapy (ART) compared to protease inhibitor-based therapy (174.1 ± 59.8 vs. 202.8 ± 47.3 ng/ml, P = 0.008), suggesting a scenario in which ART regimen-related toxicity can contribute to HAND. Plasma IGF2R levels were positively correlated with plasma VL (β coefficient 0.37, P = 0.021) and inversely correlated with current CD4+ T cell counts (β coefficient −0.04, P = 0.021), supporting our previous findings in vitro. CONCLUSIONS: Together, these results strongly implicate (1) an inverse relationship between inflammation and IGF growth factor availability and the contribution of IGF deficiencies to HAND and (2) the role of IGF2R in HIV infection and as a surrogate biomarker for HIV VL. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12974-015-0288-6) contains supplementary material, which is available to authorized users

Near-Perfect Reconstruction Oversampled Nonuniform Cosine-Modulated Filter Banks Based on Frequency Warping and Subband Merging

A novel method for designing near-perfect reconstruction oversampled nonuniform cosine-modulated filter banks is proposed, which combines frequency warping and subband merging, and thus offers more flexibility than known techniques. On the one hand, desirable frequency partitionings can be better approximated. On the other hand, at the price of only a small loss in partitioning accuracy, both warping strength and number of channels before merging can be adjusted so as to minimize the computational complexity of a system. In particular, the coefficient of the function behind warping can be constrained to be a negative integer power of two, so that multiplications related to allpass filtering can be replaced with more efficient binary shifts. The main idea is accompanied by some contributions to the theory of warped filter banks. Namely, group delay equalization is thoroughly investigated, and it is shown how to avoid significant aliasing by channel oversampling. Our research revolves around filter banks for perceptual processing of sound, which are required to approximate the psychoacoustic scales well and need not guarantee perfect reconstruction

System do badania skuteczności kodeków wideo w kodowaniu obrazu

This article presents a system for evaluating how well do video codecs perform in still image compression. As it is time consuming and tedious to directly configure and run the reference H.265 (HEVC) and H.264 (MPEG4 AVC) codecs, our tool makes experimenting easier and more efficient. The system provides a graphical user interface for conveniently and quickly preparing input files, for repeatedly running video codecs, and for analysing output data. In the background, there are algorithms for forming video sequences and configuration files, for batch executing an encoder, and for extracting information from output files. Our research was mainly aimed at speeding-up experiments related to compressing an image represented as a video sequence composed of its polyphase components. The system has allowed us to experimentally verify that, like its predecessor, the H.264, the HEVC standard needs modified entropy codes for effectively processing decimated images.Artykuł prezentuje system do badania sprawności kodeków wideo w kompresowaniu obrazu. Ponieważ bezpośrednie konfigurowanie i uruchamianie referencyjnych kodeków H.265 (HEVC) i H.264 (MPEG4 AVC) jest pracą czasochłonną i żmudną, omawiane narzędzie pozwala przeprowadzać eksperymenty łatwiej i szybciej. System jest wyposażony w graficzny interfejs użytkownika do wygodnego i sprawnego przygotowywania ˙ plików wejściowych, do wielokrotnego uruchamiania kodeków wideo i do analizowania danych wyjściowych. Interfejs opiera się na podprogramach do formowania sekwencji wideo i plików konfiguracyjnych, do wsadowego uruchamiania koderów i do wydobywania informacji z plików wynikowych. Głównym celem pracy nad systemem było przyspieszenie eksperymentów nad kodowaniem obrazu reprezentowanego jako sekwencja wideo złożona z jego składowych polifazowych. System umożliwił eksperymentalne sprawdzenie, że podobnie jak H.264, standard HEVC może skutecznie przetwarzać obrazy zdecymowane, ale wymaga to zoptymalizowania kodów entropijnych

FPGA Implementation of Short Critical Path CORDIC-Based Approximation of the Eight-Point DCT

This paper presents an efficient approach for multiplierless implementation for eight-point DCT approximation, which based on coordinate rotation digital computer (CORDIC) algorithm. The main design objective is to make critical path of corresponding circuits shorter and reduce the combinational delay of proposed scheme

Użycie FPGA i Java do szybkiego prototypowania dekodera H.264/AVC działającego w czasie rzeczywistym

This paper reports on an attempt to implement a real-time hardware H.264 video decoder. The initial results of the project are presented: a customized RISC core and some digital modules, both of which have been implemented in Xilinx FPGA. The former has to serve as a host processor that supervises the latter, which speed up the essential decoding subtasks. The system is designed and tested using a software decoder and diagnostic tools, which are implemented in Java using the object-oriented paradigm. Our experiences allow us to recommend the combination of FPGA and Java technologies as a good basis for rapid prototyping of advanced DSP algorithms.W pracy przedstawiono raport z próby implementacji działającego w czasie rzeczywistym sprzętowego dekodera wideo standardu H.264. Zaprezentowano wstępne wyniki projektu: jądro RISC i wybrane moduły cyfrowe zaimplementowane z użyciem Xilinx FPGA. Jądro ma służyć jako nadrzędny procesor sterujący pozostałymi obwodami dekodera, które przyśpieszają podstawowe etapy dekodowania. System jest projektowany i testowany w oparciu o dekoder programowy i narzędzia diagnostyczne, które są implementowane obiektowo w Javie. Uzyskane rezultaty pozwalają autorom rekomendować połączenie FPGA i Java jako dobrą podstawę do szybkiego prototypowania zaawansowanych algorytmów DSP