Showing papers by "Yi Chen published in 1994"
TL;DR: The degree to which training in noise increases robustness across noise levels is studied, and feature selection is employed to arrive at a noise-insensitive set of granulometric classifiers.
Abstract: Binary morphological granulometric size distributions were conceived by Matheron as a way of describing image granularity (or texture). Since each normalized size distribution is a probability density, feature vectors of granulometric moments result. Recent application has focused on taking local size distributions around individual pixels so that the latter can be classified by surrounding texture. The extension of the local-classification technique to gray-scale textures is investigated. It does so by using 42 granulometric features, half generated by opening granulometries and a dual half generated by closing granulometries. After training and classification of both dependent and independent data, feature extraction (compression) is accomplished by means of the Karhunen-Loeve transform. Sequential feature selection is also applied. The effect of randomly placed uniform noise is investigated. In particular, the degree to which training in noise increases robustness across noise levels is studied, and feature selection is employed to arrive at a noise-insensitive set of granulometric classifiers.
122 citations
TL;DR: In this paper, the number, strength, and nature of acid/base sites on the surface of calcined hydrotalcites were characterized using microcalorimetric and infrared spectroscopic measurements of NH[sub 3] and CO[sub 2] adsorption.
Abstract: Magnesium-aluminum hydrotalcite compounds have been synthesized without possible contamination by alkali cations. Pure hydrotalcite compounds with Mg/Al ratios from 3 to 12 were synthesized without the formation of separate phases. These materials were converted into magnesium-aluminum mixed oxides upon calcination at 773 K, showing the X-ray diffraction pattern of MgO. Microcalorimetric and infrared spectroscopic measurements of NH[sub 3] and CO[sub 2] adsorption were used to characterize the number, strength, and nature of acid/base sites on the surface of the calcined hydrotalcites. These materials do not possess acid sites and base sites with differential heats higher than 120 kJ/mol, respectively. In contrast, [gamma]-Al[sub 2]O[sub 3] possesses acid sites with differential heats from about 60 to kJ/mol, and MgO has base sites with differential heats as high as 170 kJ/mol. Infrared spectroscopy revealed that the acid sites on calcined hydrotalcites are mainly Lewis acids sites, while the base sites are oxygen anions. Calcination of hydrotalcites can be used to prepare Mg-Al-O mixed oxides with high surface are and moderate acidity and basicity. 35 refs., 11 figs., 2 tabs.
121 citations
TL;DR: The isolation and characterization of an ever expanding spectrum of hCG-related molecular forms in blood and urine have begun to enlarge the scope of clinical applications served by their measurement.
Abstract: SINCE the discovery of human chorionic gonadotropin (hCG) by Hirose (1) and Ascheim and Zondek (2) nearly three quarters of a century ago, its measurement has been the basis of pregnancy diagnosis and, coincidentally, a marker for many trophoblastic and nontrophoblastic tumors, including some tumors of the testes (3). The first measurements of hCG were by biological activity, which restricted detection to the intact, heterodimeric molecule. The advent of immunoassays in the 1960s (4) permitted not only quantification of the parent molecule but also differential estimation of gonadotropin free subunits and fragments. Since then the isolation and characterization of an ever expanding spectrum of hCG-related molecular forms in blood and urine have begun to enlarge the scope of clinical applications served by their measurement. Variations in the hCG molecule isolated from biological fluids include the following: those affecting sialic acid content (5–7) or carbohydrate structure and composition (8–11), those ...
92 citations
TL;DR: In this paper, the two-dimensional t-J model superconducts near phase separation in the regime of quarter-filling density, in agreement with previous results reported by Dagotto and Riera [Phys Rev Lett 70, 682 (1993).
Abstract: Numerical and analytical studies of several models of correlated electrons are discussed Based on exact diagonalization and variational Monte Carlo techniques, we have found indications that the two-dimensional t-J model superconducts near phase separation in the regime of quarter-filling density, in agreement with previous results reported by Dagotto and Riera [Phys Rev Lett 70, 682 (1993)] At this density the dominant channel is ${\mathit{d}}_{\mathit{x}}^{2}$-${\mathit{y}}^{2}$, but a transiton to s-wave superconductivity is observed decreasing the electronic density In addition, the one-band t-U-V model has also been studied using a mean-field approximation An interesting region of ${\mathit{d}}_{\mathit{x}}^{2}$-${\mathit{y}}^{2}$ superconductivity near phase separation is observed in the phase diagram, and its implications for recent self-consistent studies of d-wave condensates in the context of the high-${\mathit{T}}_{\mathit{c}}$ cuprates are briefly discussed Finally, the two-band Hubbard model on a chain is also analyzed Superconducting correlations near phase separation exist in this model, as it occurs in the t-J model Based on these nontrivial examples it is conjectured that electronic models tend to have superconducting phases in the vicinity of phase separation, and this regime of parameter space should be explored first when a new model for superconductivity is proposed Reciprocally, if it is established that a model does not phase separate, even in an extended parameter space, then we believe that its chances of presenting a superconducting phase are considerably reduced
80 citations
TL;DR: The genome of all hepadnaviruses has an open reading frame called the P gene, which encodes a polypeptide of 90 to 97 kDa, which suggests that the basic structure of the RNase H domain in the DHBV P gene product is required for viral RNA packaging.
Abstract: The genome of all hepadnaviruses has an open reading frame called the P gene, which encodes a polypeptide of 90 to 97 kDa. The product or products of this P gene are involved in multiple functions of the viral life cycle. These functions include a priming activity which initiates minus-strand DNA synthesis, a polymerase activity which synthesizes DNA by using either RNA or DNA templates (reverse transcriptase), a nuclease activity which degrades the RNA strand of RNA-DNA hybrids (RNase H), and involvement in packaging the RNA pregenome into nucleocapsids. In a previous study, we found that a single point mutation at position 711 in the duck hepatitis B virus (DHBV) P gene product RNase H domain prevented viral RNA packaging. In the present experiments, we have mutated additional conserved amino acids in the DHBV RNase H domain and examined the ability of viral genomes containing these mutations to package RNA and replicate viral DNA. Charged and sulfur group amino acids adjacent to Cys-711 were mutated. None of these mutants was defective in either RNA packaging or viral replication. We also tested a number of mutations on the basis of common elements in the crystal structures of Escherichia coli and human immunodeficiency virus reverse transcriptase RNase H enzymes and on the basis of the similarities of their amino acid sequences to those of the RNase H domains of DHBV and HBV. Our results revealed that the entire beta 4 strand and amino acids Leu-712, Leu-697, and Val-719 in the putative hydrophobic cores of the beta 4, alpha A, and alpha B regions, respectively, are involved in pregenomic RNA encapsidation. This suggests that the basic structure of the RNase H domain in the DHBV P gene product is required for viral RNA packaging. We used the in vitro DHBV minus-strand DNA priming system developed by Wang and Seeger (G.-H. Wang and C. Seeger, Cell 71:663-670, 1992) to test the effect of RNase H packaging mutations on P gene product enzymatic activity. While all packaging-defective mutants tested maintained DNA priming activity, levels were decreased 5- to 20-fold compared with that of the wild-type genome. This observation suggests that the hepadnavirus RNase H domain plays a role in optimizing priming of minus-strand DNA synthesis.
52 citations
TL;DR: In this paper, the effect of adding tin oxide to δ-Al2O3 has been studied in microcalorimetric and infrared spectroscopic studies of ammonia and carbon dioxide adsorption.
Abstract: Microcalorimetric and infrared spectroscopic studies of ammonia and carbon dioxide adsorption have been used to study the effects on the acid/base properties of adding tin oxide toγ-Al2O3. The addition of SnO2 toγ-Al2O3 decreases the number of strong acid sites (heats of ammonia adsorption higher than 140 kJ/mol), increases the number of weaker acid sites (heats from 110 to 130 kJ/mol), and decreases slightly the number of basic sites (heats of carbon dioxide adsorption from 70 to 150 kJ/mol). In contrast, the presence of SnO onγ-Al2O3 decreases the total number of acid sites (heats of ammonia adsorption higher than 70 kJ/mol) and eliminates most of the basic sites. Infrared spectroscopy of adsorbed ammonia reveals interactions between aluminum cations and stannous ions, leading to a decrease in the strength of the Lewis acid sites associated with aluminum cations.
47 citations
TL;DR: The separate effects of hypertension and non-insulin-dependent diabetes mellitus on insulin resistance in both nonobese and obese subjects were quantified to quantify the different effects of these diseases on each other.
Abstract: Resistance to insulin-mediated glucose disposal has been previously shown to be increased in association with obesity, high blood pressure, and non-insulin-dependent diabetes mellitus. We initiated the present study to quantify the separate effects of hypertension and non-insulin-dependent diabetes mellitus on insulin resistance in both nonobese and obese subjects. To accomplish this, 88 subjects were divided into the following five experimental groups: normal blood pressure, nonobese (n = 17); normal blood pressure, obese (n = 18); high blood pressure, nonobese (n = 18); high blood pressure, obese (n = 19); and high blood pressure, obese, non-insulin-dependent diabetes mellitus (n = 16). Plasma glucose and insulin concentrations were measured before and after a 75-g oral glucose load. Resistance to insulin-mediated glucose disposal was estimated by determining the steady-state plasma insulin and glucose concentrations during the last 30 minutes of a continuous infusion of somatostatin (5 micrograms/min), exogenous insulin (25 mU/m2 per minute), and glucose (240 mg/m2 per minute). Since the steady-state plasma insulin concentrations are similar in all subjects, the higher the steady-state plasma glucose, the more insulin resistant the individual. Nonobese subjects with normal blood pressure had the lowest plasma glucose and insulin responses and steady-state plasma glucose concentrations, and their values were significantly different from the other four groups. Obese or nonobese subjects with high blood pressure had significantly higher plasma glucose responses and steady-state plasma glucose concentrations than did their respective weight-matched control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
40 citations
TL;DR: In this article, the relative amount of cations in Ba-W-Ce complex oxides with perovskite superstructure interstitial oxygen species can be created which benefits C2 selectivity.
Abstract: Ce4+ doped Ba3 WO6 complex oxides were used as catalysts for methane oxidative coupling (MOC), and characterized by XPS and O2-TPD-MS techniques. The results indicate that the ratio of electrophilic oxygen species O− and O
2
−
to lattice oxygen on the surface is crucial for C2 selectivity. By adjusting the relative amount of cations in Ba-W-Ce complex oxides with perovskite superstructure interstitial oxygen species can be created which benefits C2 selectivity by raising the relative amount of (O− + O
2
−
) on the surface.
38 citations
TL;DR: It is shown that the examination of the density-correlation function alone is not enough to support recent claims in the literature that suggested spin and charge in the low electronic density regime of the t-J model.
Abstract: The spin- and density-correlation functions of the two-dimensional Hubbard model at low electronic density 〈n〉 are calculated in the ground state by using the power method, and at finite temperatures by using the quantum Monte Carlo technique. Both approaches produce similar results, which are in close agreement with numerical and high-temperature-expansion results for the two-dimensional t-J model. Using perturbative approximations, we show that the examination of the density-correlation function alone is not enough to support recent claims in the literature that suggested spin and charge separation in the low electronic density regime of the t-J model.
26 citations
TL;DR: A fairly quick method has been established for the production of highly condensed polyacrylamide gel-filled capillaries with inner diameters as small as 25 μm and monomer concentrations of up to over 30% T + 5% C can successfully be prepared within 5 h.
10 citations
TL;DR: In this article, the co-deposition of iron and boron atoms with borons to stabilize the amorphous structure has been studied and the results showed that the powders will become paramagnetic when the B content reaches about 70 at% and the average magnetic hyperfine field H decreases nearly linearly with a slope of about −4.7 kOe per B atom.
Abstract: By altering the preparation conditions, systematic variation of Fe 100− x B x ultrafine amorphous powders with 29 ≤x≤40 has been realized by the chemical reduction method. The preparation mechanism, the co-deposition of iron and boron atoms with boron atoms to stabilize the amorphous structure, was studied. The samples were characterized and investigated mainly by Mossbauer spectroscopy and differential scanning calorimetry. It is found that, with increasing boron contents in the samples, the average magnetic hyperfine field H decreases nearly linearly with a slope of about −4.7 kOe per B atom and the crystallization temperature shows a tendency, to increase. From the linear relationship of H vs. x , electron transfer from B to Fe was suggested. It is extrapolated that the powders will become paramagnetic when the B content reaches about 70 at.% and the H for pure amorphous iron is about 340 kOe, in nice agreement with the cases in amorphous ribbons.
TL;DR: The ultrasonic method appears to provide a high-precision system for measuring animal behaviors, and when the animal activity was measured with an infrared light system, the activity responses to drugs were not detectable.
01 Jan 1994
TL;DR: Adaptive reconstructive τ -openings are to employed to recover signal from noise in the binary union-noise model using a Markov chain whose transitions occur at each encounter with a grain when scanning the image.
Abstract: Adaptive reconstructive τ -openings are to employed to recover signal from noise in the binary union-noise model. Openings are parameterized in accordance with Euclidean granulometric representation, the parameter being restricted to nonnegative integers. The filter-parameter space is treated as the countably infinite state space in a Markov chain whose transitions occur at each encounter with a grain when scanning the image. An upward or downward transition occurs when a noise or signal grain, respectively, is misrecognised.
TL;DR: In this paper, the relation between the catalytic performance and the composition of the catalyst surface has been studied by means of X-ray diffraction, CO2 temperature-programmed desorption, O2 temperature programmable desorcization, and laser Raman spectroscopy techniques.
Abstract: Alkaline earth metal titanates used as catalysts for methane oxidative coupling have been prepared by (1) solid state reaction and (2) spray combustion methods. It has been established that the bulk phase of all the samples prepared have a perovskite-like structure and that the surface composition and hence the catalytic performance for methane oxidative coupling of the samples differ considerably and are dependent on the preparation method. The relation between the catalytic performance and the composition of the catalyst surface has been studied by means of X-ray diffraction, CO2 temperature-programmed desorption, O2 temperature-programmed desorption. X-ray photoelectron spectroscopy, and laser Raman spectroscopy techniques. A high surface concentration of Ti4+ cations leads to the complete oxidation of methane, and a high surface concentration of alkaline earth metal cations facilitates the formation of C2 hydrocarbons. Surface basicity is necessary for methane oxidative coupling and the oxygen adsorbed on the basic site is also indispensable; in fact, the adsorbed electron deficient species, i.e. O− and O−2, on the surface play a crucial role in methane conversion and C2 selectivity. The adsorption of carbon dioxide could compete for the adsorption site of oxygen, and exerts an unfavorable influence in methane oxidative coupling.