Search PubMed⌕ Search

Biomedical subjects

J Qi

Publications and source records attributed to J Qi.

At least 37 records · Page 2Linked to original sources
PubMed2001

Prediction of programmed-temperature retention values of naphthas by wavelet neural networks.

The wavelet neural network (WNN) was used to predict the programmed-temperature retention values of naphthas. In WNN, a Morlet mother wavelet was used as a transfer function, and the convergence speed was faster than other neural networks. Sixty-four compounds (selected randomly from 94) were used as a training set, and the 30 remaining compounds were used as a test set. A very satisfactory result was obtained only after about 8000 training epochs. The other two methods, the artificial neural network (ANN) and the Simpson integral method, were also used for this study. The comparison of results obtained from three methods showed that the WNN is the most suitable tool in predicting programmed-temperature retention values of naphthas, consequently this method can be used to provide reliable data for the petrochemical industry.

Journal Article↗
PubMed2001

Neuritogenic cerebrosides from an edible Chinese mushroom. Part 2: Structures of two additional termitomycesphins and activity enhancement of an inactive cerebroside by hydroxylation.

Termitomycesphins E and F, novel cerebrosides that are hydroxylated around the middle of the long-chain base (LCB), have been isolated from the edible Chinese mushroom Termitomyces albuminosus (Berk.) Heim. ('Jizong' in Chinese) together with termitomycesphins A-D, and shown to induce neuronal differentiation in rat PC12 cells. Their stereostructures have been determined based on their chemical derivatization and spectroscopic analysis. The major cerebroside obtained from the same mushroom was not hydroxylated around the middle of the LCB and was inactive against PC12 cells, suggesting the importance of the extra hydroxyl group on LCB. The Di- and tetrahydroxylation of this inactive cerebroside resulted in the enhancement of its neuritogenic activity.

Agaricales↗
PubMed2001

Theoretical study of lesion detectability of MAP reconstruction using computer observers.

The low signal-to-noise ratio (SNR) in emission data has stimulated the development of statistical image reconstruction methods based on the maximum a posteriori (MAP) principle. Experimental examples have shown that statistical methods improve image quality compared to the conventional filtered backprojection (FBP) method. However, these results depend on isolated data sets. Here we study the lesion detectability of MAP reconstruction theoretically, using computer observers. These theoretical results can be applied to different object structures. They show that for a quadratic smoothing prior, the lesion detectability using the prewhitening observer is independent of the smoothing parameter and the neighborhood of the prior, while the nonprewhitening observer exhibits an optimum smoothing point. We also compare the results to those of FBP reconstruction. The comparison shows that for ideal positron emission tomography (PET) systems (where data are true line integrals of the tracer distribution) the MAP reconstruction has a higher SNR for lesion detection than FBP reconstruction due to the modeling of the Poisson noise. For realistic systems, MAP reconstruction further benefits from accurately modeling the physical photon detection process in PET.

Computer Simulation↗
PubMed2001

Congenital corneal opacification in De Barsy syndrome.

A newborn male was noted to have bilateral congenital corneal opacification. Findings from examination disclosed a variety of dysmorphic features, including cutis laxa, progeroid aspect, short stature, multiple hyperextensible subluxated joints, muscular hypotonia, and hyperreflexia. Bilateral penetrating keratoplasties were performed; histopathologic examination revealed diffuse epithelial thickening, loss of the Bowman layer, and stromal attenuation with anterior stromal scarring. Special stains showed no deposition of abnormal material in the corneas. Electron microscopy demonstrated absence of Bowman layer differentiation with a paucity of collagen fibers, as well as extensive small elastic fibers in the anterior stroma. The diagnosis of De Barsy syndrome was made, a rare progeroid syndrome associated with characteristic ocular, facial, skeletal, dermatologic, and neurologic abnormalities. De Barsy syndrome should be included in the differential diagnosis of congenital corneal opacification; its distinctive clinical features enable the clinician to easily differentiate it from other causes of congenitally cloudy corneas.

Abnormalities, Multiple↗
PubMed2001

[Simulation study of electrode configurations for cardiac stroke volume calculation by 3-dimensional finite element method].

This is a research in Kubicek electrode configurations for cardiac stroke volume calculation from the angle of Kubicek model simulation by 3-dimensional finite element method. In the process of computer simulation, we have studied, respectively, the effect of the width, thickness, and material property (specific resistance) of potential electrode band on cardiac stroke volume calculation in order to guide the choice of electrode configurations in the clinic. The simulation results showed that in Kubicek electrode configurations, its all properties of the potential electrode band affected the impedance results for cardiac stroke volume calculation, one main factor of which is the choice of the material property. Therefore, we have to attend to the choice of Kubicek electrode configurations while calculating SV by Kubicek method in order to improve the accuracy of SV calculation.

Electrodes↗
PubMed2001

[Degradation of nitrobenzene in water by electrohydrodynamic DC discharge].

In this paper, the experimental results with respect to the degradation of nitrobenzene in water using electrohydrodynamic DC discharge were presented. The DC voltage was 40 kV, the degradation efficiency in the first discharge process reached 50%, the total degradation efficiency in the second discharge process reached 80%. The products contained acetone. At the same time, the degradation efficiency variation with the voltage polarity, flux, and concentration were studied. These studies will be helpful to the treatment of organic wastewater.

Electrolysis↗
PubMed2001

Alleviation of hypoxic pulmonary vascular structural remodeling by L-arginine.

OBJECTIVE: To explore the effect of L-arginine on hypoxic pulmonary vascular structural remodeling and its possible mechanisms. METHODS: Eighteen Wistar rats were randomly divided into three groups: the hypoxia group, the hypoxia with L-arginine group and the control group. Pulmonary artery mean pressure was evaluated with right cardiac catheterization. Pulmonary vascular structural changes were also observed. Plasma concentration of nitric oxide (NO) was measured via spectrophotometry, and endothelin-1 (ET-1) mRNA expression in pulmonary artery endothelial cells was detected using in situ hybridization. RESULTS: The pulmonary artery mean pressure was significantly high in hypoxic rats than in normal controls (20.33 +/- 2.18 mm Hg vs 15.38 +/- 1.05 mm Hg, P < 0.05). Microstructural and ultrastructural analysis revealed the development of hypoxic pulmonary vascular structural remodeling in the hypoxic rats. Meanwhile, the plasma NO concentration was markedly lower in the hypoxic rats than in controls (P < 0.05). The expression signals of ET-1 mRNA by pulmonary artery endothelial cells of hypoxic rats strengthened obviously. L-arginine ameliorated pulmonary hypertension (16.73 +/- 1.35 mm Hg vs 20.33 +/- 2.18 mm Hg, P < 0.05) as well as pulmonary vascular structural remodeling in the hypoxic rats in association with an increase in plasma NO concentration (P < 0.05) and inhibited ET-1 mRNA expression by the endothelial cells of pulmonary arteries. CONCLUSION: L-arginine might play an important role in the regulation of hypoxic pulmonary vascular structural remodeling and hypoxic pulmonary hypertension. The mechanism is probably related to promoting NO production and, as a result, inhibiting ET-1 mRNA expression by pulmonary artery endothelial cells in hypoxic rats.

Animals↗
PubMed2001

[The predomination of rotavirus G3 serotype among children with diarrhea in Lulong County in 1998].

OBJECTIVE: To investigate the epidemiology of rotavirus diarrhea among children in rural population. METHODS: 120 stool specimens collected from children with diarrhea during the winter of 1998 in Lulong County, Hebei Province were examined for rotavirus by PAGE and ELISA and for serotype by ELISA and PCR. RESULTS: Rotavirus was detected in children aged between 2-24 months. The positive rate of rotavirus was 39.2% and the ratio of male to female was 1-1.47. All rotavirus RNA profiles were long pattern. The distribution of rotavirus serotypes was type 3(61.7%), followed by type 1(36.2%), and type 4(6.4%). CONCLUSIONS: The epidemiology of rotavirus diarrhea during 1998 rotavirus season in Lulong County was similar to that of other regions in China, but rotavirus serotype G3 was a prevalent strain in Lulong County, which was uncommon and different from the predominant G1 in other places throughout China.

Child, Preschool↗
PubMed2000

The relationship between marijuana initiation and dropping out of high school.

The prevalence of marijuana use among young people has risen rapidly in recent years, causing concern over the potential impact on academic performance of such use. While recent studies have examined the effect of alcohol use on educational attainment, they have largely ignored the potential negative effects of other substances, such as marijuana. This paper examines whether the relationship between the initiation of marijuana use and the decision to drop out of high school varies with the age of dropout or with multiple substance use. Data are from a longitudinal survey of 1392 adolescents aged 16-18 years. The results suggest that marijuana initiation is positively related to dropping out of high school. Although the magnitude and significance of this relationship varies with age of dropout and with other substances used, it is concluded that the effect of marijuana initiation on the probability of subsequent high school dropout is relatively stable, with marijuana users' odds of dropping out being about 2.3 times that of non-users. Implications of these conclusions are considered for both policy makers and researchers.

Adolescent↗
PubMed2000

The Perturbation between the G(1)Pi(g) and 2(1)Delta(g) States of (7)Li(2).

We have observed the rotational levels in the v = 2, 3, 5, 6, 7, and 8 vibrational manifolds of the 2(1)Delta(g) state of (7)Li(2) via the A(1)Sigma(+)(u) intermediate levels by DeltaLambda = 2 transitions. This violation of the DeltaLambda = 0, +/-1 selection rule is due to the interaction with the G(1)Pi(g) state. Band-by-band deperturbations of the G(1)Pi(g) approximately 2(1)Delta(g) (v(Pi), v(Delta)) = (11, 2), (12, 3), (15, 5), (16, 6), (18, 7), and (19, 8) bands have been performed. Deperturbed molecular constants and rotational-electronic interaction parameters are reported here. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Mechanisms underlying regulated CFTR trafficking.

Stimulation of membrane capacitance and cell surface labeling of epitope-tagged CFTR provide evidence of cAMP-regulated CFTR trafficking. Co-expression of syntaxin 1A inhibits cAMP-stimulated current and capacitance changes in CFTR expressing cells and blocks cAMP-induced increases in cell surface CFTR. Inhibition of CFTR trafficking by syntaxin over-expression suggests a role for SNARE proteins in this process. CFTR phosphorylation may alter physical interactions with SNARE proteins to regulate plasma membrane CFTR density.

Cyclic AMP↗
PubMed2000

Resolution and noise properties of MAP reconstruction for fully 3-D PET.

We derive approximate analytical expressions for the local impulse response and covariance of images reconstructed from fully three-dimensional (3-D) positron emission tomography (PET) data using maximum a posteriori (MAP) estimation. These expressions explicitly account for the spatially variant detector response and sensitivity of a 3-D tomograph. The resulting spatially variant impulse response and covariance are computed using 3-D Fourier transforms. A truncated Gaussian distribution is used to account for the effect on the variance of the nonnegativity constraint used in MAP reconstruction. Using Monte Carlo simulations and phantom data from the microPET small animal scanner, we show that the approximations provide reasonably accurate estimates of contrast recovery and covariance of MAP reconstruction for priors with quadratic energy functions. We also describe how these analytical results can be used to achieve near-uniform contrast recovery throughout the reconstructed volume.

Algorithms↗
PubMed2000

Comparison of 3-D maximum a posteriori and filtered backprojection algorithms for high-resolution animal imaging with microPET.

We have evaluated the performance of two three-dimensional (3-D) reconstruction algorithms with data acquired from microPET, a high resolution tomograph dedicated to small animal imaging. The first was a linear filtered-backprojection algorithm (FBP) with reprojection of the missing data, and the second was a statistical maximum a posteriori probability algorithm (MAP). The two algorithms were evaluated in terms of their resolution performance, both in phantoms and in vivo. Sixty independent realizations of a phantom simulating the brain of a baby monkey were acquired, each containing three million counts. Each of these realizations was reconstructed independently with both algorithms. The ensemble of the 60 reconstructed realizations was used to estimate the standard deviation as a measure of the noise for each reconstruction algorithm. More detail was recovered in the MAP reconstruction without an increase in noise relative to FBP. Studies in a simple cylindrical compartment phantom demonstrated improved recovery of known activity ratios with MAP. Finally, in vivo studies also demonstrated a clear improvement in spatial resolution using the MAP algorithm. The quantitative accuracy of the MAP reconstruction was also evaluated by comparison with autoradiography and direct well counting of tissue samples and was shown to be superior.

Algorithms↗
PubMed2000

List-mode maximum-likelihood reconstruction applied to positron emission mammography (PEM) with irregular sampling.

We present a preliminary study of list-mode likelihood reconstruction of images for a rectangular positron emission tomograph (PET) specifically designed to image the human breast. The prospective device consists of small arrays of scintillation crystals for which depth of interaction is estimated. Except in very rare instances, the number of annihilation events detected is expected to be far less than the number of distinguishable events. If one were to histogram the acquired data, most histogram bins would remain vacant. Therefore, it seems natural to investigate the efficacy of processing events one at a time rather than processing the data in histogram format. From a reconstruction perspective, the new tomograph presents a challenge in that the rectangular geometry leads to irregular radial and angular sampling, and the field of view extends completely to the detector faces. Simulations are presented that indicate that the proposed tomograph can detect 8-mm-diameter spherical tumors with a tumor-to-background tracer density ratio of 3:1 using realistic image acquisition parameters. Spherical tumors of 4-mm diameter are near the limit of detectability with the image acquisition parameters used. Expressions are presented to estimate the loss of image contrast due to Compton scattering.

Algorithms↗
PubMed2000

Increased detectability of alpha brain glutamate/glutamine in neonatal hypoxic-ischemic encephalopathy.

BACKGROUND AND PURPOSE: Proton MR spectroscopy (MRS) detectability of brain glutamate/glutamine (Glx) is increased in hypoxic-ischemic insults and is implicated in the neuronal injury and death that follows. Our aim was to correlate the proton MRS detectability of alpha-CH protons of Glx (alpha-Glx) with the Sarnat stage of neonatal hypoxic-ischemic encephalopathy (HIE). METHODS: Initial and follow-up proton MRS studies at 1.9 T were performed in 28 neonates aged 1 to 7 days (seven healthy control subjects and 21 with HIE: 10 mild, nine moderate, and two severe) and in 12 neonates aged 13 to 17 days (12 with HIE: eight mild, three moderate, and one severe), respectively. Both point-resolved spectroscopy (PRESS) and stimulated-echo acquisition mode (STEAM) sequences were used. The spectral volume of interest was in the basal ganglia, thalami, and adjoining regions. The detectability of alpha-Glx was assessed by two different parameters: the detection rate of the alpha-Glx peak and the peak-area ratio of alpha-Glx to creatine and phosphocreatine. RESULTS: On both the initial and follow-up PRESS studies, all the neonates with moderate and severe HIE showed an alpha-Glx peak, compared with one healthy control subject in the initial study and one neonate with mild HIE in both the studies. They also demonstrated a significantly higher peak-area ratio of alpha-Glx/(creatine and phosphocreatine) on both the initial and follow-up studies. The peak-area ratios in neonates with HIE positively correlated with the Sarnat stage of HIE on both the initial and follow-up studies. Neonates with moderate and severe HIE also showed a consistently higher alpha-Glx peak on both the initial and follow-up studies with the STEAM sequence. CONCLUSION: Proton MRS detectability of alpha-Glx is increased in moderate and severe HIE and correlates with the Sarnat stage of HIE.

Brain↗