The Standard Hough Transform is a popular method in image processing and is traditionally estimated using histograms. Densities modeled with histograms in high dimensional space and/or with few observations, can be very sparse and highly demanding in memory. In this paper, we propose first to extend the formulation to continuous kernel estimates. Second, when dependencies in between variables are well taken into account, the estimated density is also robust to noise and insensitive to the choice of the origin of the spatial coordinates. Finally, our new statistical framework is unsupervised (all needed parameters are automatically estimated) and flexible (priors can easily be attached to the observations). We show experimentally that our new modeling encodes better the alignment content of images. 相似文献
In this paper, we introduce a Bayesian approach, inspired by probabilistic principal component analysis (PPCA) (Tipping and Bishop in J Royal Stat Soc Ser B 61(3):611–622, 1999), to detect objects in complex scenes using appearance-based models. The originality of the proposed framework is to explicitly take into account general forms of the underlying distributions, both for the in-eigenspace distribution and for the observation model. The approach combines linear data reduction techniques (to preserve computational efficiency), non-linear constraints on the in-eigenspace distribution (to model complex variabilities) and non-linear (robust) observation models (to cope with clutter, outliers and occlusions). The resulting statistical representation generalises most existing PCA-based models (Tipping and Bishop in J Royal Stat Soc Ser B 61(3):611–622, 1999; Black and Jepson in Int J Comput Vis 26(1):63–84, 1998; Moghaddam and Pentland in IEEE Trans Pattern Anal Machine Intell 19(7):696–710, 1997) and leads to the definition of a new family of non-linear probabilistic detectors. The performance of the approach is assessed using receiver operating characteristic (ROC) analysis on several representative databases, showing a major improvement in detection performances with respect to the standard methods that have been the references up to now.This revised version was published online in November 2004 with corrections to the section numbers. 相似文献
In order to utilise sardinelle (Sardinellaaurita) protein by-products, which is normally discarded as industrial waste in the process of fish manufacturing, heads and viscera proteins were hydrolysed by different proteases to obtain antioxidative peptides. All hydrolysates showed different degrees of hydrolysis and varying degrees of antioxidant activities. Hydrolysate generated with crude enzyme extract from sardine (Sardinapilchardus) displayed high antioxidant activity, and the higher DPPH radical-scavenging activity (87 ± 2.1% at 2 mg/ml) was obtained with a degree of hydrolysis of 6%. This hydrolysate was fractionated by size exclusion chromatography on a Sephadex G-25 into eight major fractions (P1–P8). Fraction P4, which exhibited the highest DPPH scavenging activity, was then fractionated by reversed-phase high performance liquid chromatography (RP-HPLC). Seven antioxidant peptides were isolated. The molecular masses and amino acids sequences of the purified peptides were determined using ESI-MS and ESI-MS/MS, respectively. Their structures were identified as Leu-His-Tyr, Leu-Ala-Arg-Leu, Gly-Gly-Glu, Gly-Ala-His, Gly-Ala-Trp-Ala, Pro-His-Tyr-Leu and Gly-Ala-Leu-Ala-Ala-His. The first peptide displayed the highest DPPH radical-scavenging activity (63 ± 1.57%; at 150 μg/ml) among these peptides. 相似文献
The angiotensin I-converting enzyme (ACE) inhibitory activities of protein hydrolysates prepared from heads and viscera of sardinelle (Sardinella aurita) by treatment with various proteases were investigated. Protein hydrolysates were obtained by treatment with Alcalase®, chymotrypsin, crude enzyme preparations from Bacillus licheniformis NH1 and Aspergillus clavatus ES1, and crude enzyme extract from sardine (Sardina pilchardus) viscera. All hydrolysates exhibited inhibitory activity towards ACE. The alkaline protease extract from the viscera of sardine produced hydrolysate with the highest ACE inhibitory activity (63.2 ± 1.5% at 2 mg/ml). Further, the degrees of hydrolysis and the inhibitory activities of ACE increased with increasing proteolysis time. The protein hydrolysate generated with alkaline proteases from the viscera of sardine was then fractionated by size exclusion chromatography on a Sephadex G-25 into eight major fractions (P1–P8). Biological functions of all fractions were assayed, and P4 was found to display a high ACE inhibitory activity. The IC50 values for ACE inhibitory activities of sardinelle by-products protein hydrolysates and fraction P4 were 1.2 ± 0.09 and 0.81 ± 0.013 mg/ml, respectively. Further, P4 showed resistance to in vitro digestion by gastrointestinal proteases. The amino acid analysis by GC/MS showed that P4 was rich in phenylalanine, arginine, glycine, leucine, methionine, histidine and tyrosine. The added-value of sardinelle by-products may be improved by enzymatic treatment with visceral serine proteases from sardine. 相似文献
CYP2J2 is the main epoxygenase in the heart that is responsible for oxidizing arachidonic acid to cis-epoxyeicosatrienoic acids (EETs). Once formed, EETs can then be hydrolyzed by soluble epoxide hydrolase (sEH, encoded by EPHX2) or re-esterified back to the membrane. EETs have several cardioprotective properties and higher levels are usually associated with better cardiac outcomes/prognosis. This study investigates how cardiovascular disease (CVD) can influence total EET levels by altering protein expression and activity of enzymes involved in their biosynthesis and degradation. Diseased ventricular cardiac tissues were collected from patients receiving Left Ventricular Assist Device (LVAD) or heart transplants and compared to ventricular tissue from controls free of CVD. EETs, and enzymes involved in EETs biosynthesis and degradation, were measured using mass spectrometric assays. Terfenadine hydroxylation was used to probe CYP2J2 activity. Significantly higher cis- and trans-EET levels were observed in control cardiac tissue (n = 17) relative to diseased tissue (n = 24). Control cardiac tissue had higher CYP2J2 protein levels, which resulted in higher rate of terfenadine hydroxylation, compared to diseased cardiac tissues. In addition, levels of both NADPH-Cytochrome P450 oxidoreductase (POR) and sEH proteins were significantly higher in control versus diseased cardiac tissue. Overall, alterations in protein and activity of enzymes involved in the biosynthesis and degradation of EETs provide a mechanistic understanding for decreased EET levels in diseased tissues. 相似文献
The photochemically induced grafting polymerization of various alkyl acrylates onto cross‐linked poly(hydroxyethyl methacrylate) (PHEMA) was performed to reduce the hydrophilicity of the swellable network. Butyl, 2‐ethylhexyl and lauryl acrylate were used as monofunctional monomers for increasing the hydrophobic character, whereas hexanediol diacrylate was used as a multifunctional monomer with the additional feature of forming networks. The various steps of the grafting procedure were examined sequentially so as to optimize the overall hydrophobing effect. The grafting yield was shown to depend primarily of PHEMA swelling in the considered ethanol/monomer mixture. In spite of their high specific hydrophobic character, alkyl monoacrylates were shown to be less efficient because of lower grafting yield. Grafting initiation by hydrogen abstraction with benzophenone or by homolytic cleavage of a hydroxyalkyl‐phenone resulted in comparable grafting yields even with monofunctional monomers. The hardness measured for the water swollen rubbery materials correlated well to the equilibrium water content.
Shore A hardness as a function of the swelling ratio in water at T = 22 °C for grafted and ungrafted PHEMA hydrogels (same samples as those described in Table 5 ). 相似文献
The structure and properties of protein gels depend on the conditions under which they are formed. Here, we assessed the susceptibility of protein to simulated gastro-duodenal digestion of weak gels with contrasting structures, produced from either purified bovine β-lactoglobulin (β-Lg) or whey protein isolate (WPI) at pH ranging from 2.5 to 6.5 and using different heating regimes. Gels formed close to the isoelectric point proved to be very resistant to simulated gastric digestion, with more than 85% of β-Lg remaining and in the simulated duodenal phase of digestion. The sample heated to 85 °C was most resistant with over 40% remaining. In the WPI sample heated to 85 °C, more than 20% of the original β-Lg content remained undigested after simulated gastro-duodenal proteolysis. These results suggest that firm particulate gels can persist longer in the GI tract and may be useful in inducing satiety and thus provide another weapon in the fight against obesity. 相似文献
Protein hydrolysates are of a significant interest, due to their potential application as a source of bioactive peptides in nutraceutical and pharmaceutical domains. The present study was focused on the effect of protein hydrolysate from smooth hound (Mustelus mustelus) (SHPH) in the regulation of components of the food intake control such as satiety. SHPH was produced by intestinal digestive proteases from the same species. The amino acid analysis by GC/MS showed that the hydrolysate was rich in leucine, alanine, glycine, threonine, serine, lysine and glutamate. The molecular weights of peptides in SHPH were estimated by ESI-MS to be between 200 and 2500 Da. Biological in vivo capacities of SHPH in rats were evaluated by determination of the CCK-like peptides and insulin content using a clinical human radioimmunoassay. The food intake and the body weight of rats were measured during the period of treatment. Rats treated with SHPH showed a significant decrease in body weight at the end of treatment, as well as a decrease of food intake. Our findings revealed a possible mechanism of the beneficial effects of SHPH in appetite regulation, and this might be important to prevent the risk of a number of medical conditions including type II diabetes. 相似文献