Biomedical subjects

Deyu Li

Publications and source records attributed to Deyu Li.

At least 19 recordsLinked to original sources

PubMed2026

Genomic surveillance reveals escalating antimicrobial resistance and plasmid diversity in clinical Salmonella 1,4,[5],12:i:- ST34 isolates from Guizhou Province, China.

INTRODUCTION: Salmonella 1,4,[5],12:i:- ST34 has emerged as a significant public health issue due to its association with various antimicrobial resistance genes (ARGs) and transferable plasmids. However, its genomic characteristics and potential influence on public health in Guizhou have not been comprehensively assessed. METHODS: From 2019 to 2023, a 5-year surveillance was conducted in nine cities (prefectures) of Guizhou Province. We integrated phenotypic and genomic analyses of 281 clinical Salmonella 1,4,[5],12:i:- ST34 isolates to investigate the prevalence of ARGs and plasmids and to analyze the molecular epidemiology and evolution. RESULTS: The isolates exhibited resistance to first-line antibiotics, with 22.4% for ciprofloxacin, 11.4% for azithromycin, 18.5% for ceftazidime, and 39.1% for cefotaxime. ARGs showed substantial agreement with phenotypes for tetracycline, macrolides, third-generation cephalosporins (3GCs), carbapenems, and colistin (80.8-100.0% consistency; Kappa: 0.50-1.00). Plasmid analysis identified IncQ1 (84.3%) and IncHI2/IncHI2A (26.3%) as the main replicons, with the variety of plasmid replicons increasing from 7 to 21 over the 5 years. ARGs associated with resistance to critically important antibiotics (CIAs) were frequently predicted to be located on plasmid-associated contigs, with significant associations observed between IncHI2/IncHI2A plasmids and ARGs conferring resistance to fluoroquinolones, macrolides, and cephalosporins (P < 0.05). Molecular typing divided 281 isolates into 37 cgSTs, with cgST52428 being the most common. Molecular epidemiological analysis revealed that Guizhou isolates primarily clustered together, sharing close genetic ties with those from Sichuan and Guangdong, and exhibited the highest genetic similarity to pork-derived isolates. Phylogenetic analysis revealed clustering of CIA-resistant ARGs and plasmids in Clades 4 and 5, with a significant association between IncHI2/IncHI2A plasmids and CIA-resistant ARGs (χ2 = 112.12, P < 0.001). Additionally, class 1 integron was associated with higher ARG burdens, while virulence-associated genes were conserved and predominantly chromosome-associated. Gene-content analysis revealed that isolates in Clades 4 and 5 harbored the largest mean gene complements, and cgST52428 isolates also harbored the largest among dominant cgSTs. DISCUSSION: This study presents a comprehensive genomic profile of Salmonella 1,4,[5],12:i:- ST34 in Guizhou, providing essential data for exploring the resistance characteristics and investigating the molecular epidemiology of Salmonella 1,4,[5],12:i:-.

ST34↗

PubMed2026

pH Tunes the DNA Repair Efficiency and Strand Preference of the AlkB Family Enzymes.

AlkB-family Fe(II)/2-oxoglutarate-dependent dioxygenases repair alkylated nucleic acid lesions through oxidative dealkylation and play important roles in genome maintenance. 1-Methyl-2'-deoxyadenosine (1mA) and 3-methyl-2'-deoxycytidine (3mC) are well-established substrates of AlkB, ALKBH2, and ALKBH3. Although these enzymes have been extensively studied, the influence of proton concentration (pH) on their catalytic behavior and strand preference remains poorly defined. Here, we systematically examined how pH modulates the activity of the prototypical bacterial AlkB and the human homologues ALKBH2 and ALKBH3 using defined DNA substrates in both single-stranded (ssDNA) and double-stranded (dsDNA) contexts containing 1mA and 3mC lesions. Across a broad pH range, all three enzymes mainly exhibit bell-shaped activity profiles with distinct optima. The prevailing view in the field is that AlkB preferentially repairs these lesions in ssDNA, ALKBH2 favors dsDNA, and ALKBH3 prefers ssDNA. However, our results demonstrate that pH influences the catalytic efficiency and strand utilization in a substrate- and enzyme-dependent manner. AlkB maintains a consistent ssDNA preference for 3mC but exhibits variable strand preference for 1mA at different pH values. ALKBH2 retains a strong dsDNA preference for 1mA across all conditions but shows a clear pH-dependent strand switch for 3mC, favoring ssDNA under acidic conditions and preferring dsDNA at neutral to alkaline pH conditions. In contrast, ALKBH3 consistently favors ssDNA for 3mC but exhibits pH-dependent strand preference for 1mA. Our results show that the reported strand preferences largely hold at pH 7.0-8.0 but are not complete, as strand utilization and pH optima vary by enzyme and substrate. The observations demonstrate that proton availability strongly influences AlkB-family catalysis and is an important factor in how these enzymes process damaged DNA. These findings may also aid the optimization of AlkB-based protein engineering and sequencing technologies.

Hydrogen-Ion Concentration↗

PubMed2006

Hydrodynamic lubrication in nanoscale bearings under high shear velocity.

The setting up process in a nanoscale bearing has been modeled by molecular dynamics simulation. Contrary to the prediction from the classical Reynolds' theory, simulation results show that the load capacity of the nanoscale bearing does not increase monotonically with the operation speed. This is attributed to the change of the local shear rate, which will decrease with the shear velocity of the bearing as the shear velocity exceeds a critical value, i.e., the local shear rate has an upper limit. A simple nonlinear dynamic model indicates that the momentum exchange between the liquid and the solid wall is reduced with the shear velocity when the shear velocity is above a critical value. The weak momentum exchange results in a decrease of the local shear rate, which in turn causes a sharp increase of the slip length.

Journal Article↗

PubMed2006

Isotope effect on the thermal conductivity of boron nitride nanotubes.

We have measured the temperature-dependent thermal conductivity kappa(T) of individual multiwall boron nitride nanotubes using a microfabricated test fixture that allows direct transmission electron microscopy characterization of the tube being measured. kappa(T) is exceptionally sensitive to isotopic substitution, with a 50% enhancement in kappa(T) resulting for boron nitride nanotubes with 99.5% 11B. For isotopically pure boron nitride nanotubes, kappa rivals that of carbon nanotubes of similar diameter.

Journal Article↗

PubMed2006

[A method based on image processing and analyzing technology for estimating the activity of mesenchymal stem cells].

Cell culture is one of the usual methods for studying living cell and tissue, the method presented in this paper is based on image processing and analyzing technology for activity estimation of mesenchymal stem cells (MSCs). The existing activity estimation methods are costly, complex and invasive. In this method, thresholding is used to preprocess image and to separate out the growth hallow. Then the area is calculated by counting the pixels of the growth hallow. The changes of the activity estimated by this method are similar to those by corresponding cellular experiments. Compared with the existing methods in biology, medicine or medical cellular science, this method is easier, faster, cost-effective and non-invasive. The proposed method has been proved to be efficient by primary experiments of MSCs.

Animals↗

PubMed2006

[Fast edge extraction for ultrasound image of breast tumor based on fuzzy number].

An accurate edge extraction method for the ultrasound breast tumor image is useful for classifying tumors as benign or malignant. This paper refers to a fast technique to extract edge of breast tumor from ultrasound image. This method uses the triangular fuzzy number to build up a fuzzy number plane whose basic unit is the marching square. It is possible to visualize at once the results obtained using different presumption levels. Experiments of benign and malignant breast tumor in ultrasound images have shown that our method can extract the breast tumor edge faster than many conventional methods can do separately, and the results are reliable and credible. Our experiments demonstrate that it can be efficiently used to extract the edge of breast tumor from the ultrasound image.

Breast Neoplasms↗

PubMed2006

[Computer-aided diagnosis of fatty liver based on ultrasonic images].

This study aims to provide a computer-aided method for the diagnosis of fatty liver by B-scan ultrasonic imaging. Fatty liver is referred to the infiltration of triglycerides and other fats of the liver cells, which affected the texture of liver tissue. In this paper, some features including mean intensity ratio, as well as angular second moment, entropy and inverse differential moment of gray level co-occurrence matrix were extracted from B-scan ultrasonic liver images. Feature vectors which indicated two classes of images were created with the four features. Then we used kappa-means clustering algorithm, self-organized feature mapping (SOFM) artificial neural network and back-propagation (BP) artificial neural network to classify these vectors. The accuracy rate of kappa-means clustering algorithm was 100% for normal liver and 63.6% for fatty liver. The results of SOFM neural network showed that the accuracy rate was 84.8% for normal liver and 90.9% for fatty liver. The accuracy rate of neural network was 100% both for normal liver and fatty liver. This technology could detect the characteristics of B-scan images of normal liver and fatty liver more accurately. It could greatly improve the accuracy of the diagnosis of fatty liver.

Diagnosis, Differential↗

PubMed2006

[Review of nonlinear filters for medical ultrasonic images].

Ultrasound medical imaging has been widely applied in clinic diagnoses because of its real-time, non-invasiveness and convenience. However, it suffers from severe speckle noises. Until now, a lot of filtering algorithms have been proposed, but none of them is satisfactory. In this paper, four nonlinear filter methods, based on median filter, wavelet decomposition and anisotropic diffusion, are systematically reviewed. Finally, the prospect of the nonlinear filtering method is discussed.

Algorithms↗

PubMed2006

[The recognition of breast tumor based on ultrasonic image contour features].

The purpose of this article is to evaluate the role of quantitative margin features in the computer-aided diagnosis of malignant and benign solid breast masses using sonographic imaging. The tumour was seperated by the expert. Three contour features circurity (C), area ratio (A) and length width ratio (LWR) was caculated from the tumour contour. Then back-propagation (BP) neural network with contour features was used to classify tumors into benign and malignant. Results from 119 ultrasonic images have been applied in this experiment. BP neural network yielded the following results: 89.7% and 73.5% respectively. The methods applied in this paper are helpful to raise the correctance of breast cancer diagnosis.

Breast Neoplasms↗

PubMed2005

Electrostatic control of ions and molecules in nanofluidic transistors.

We report a nanofluidic transistor based on a metal-oxide-solution (MOSol) system that is similar to a metal-oxide-semiconductor field-effect transistor (MOSFET). Using a combination of fluorescence and electrical measurements, we demonstrate that gate voltage modulates the concentration of ions and molecules in the channel and controls the ionic conductance. Our results illustrate the efficacy of field-effect control in nanofluidics, which could have broad implications on integrated nanofluidic circuits for manipulation of ions and biomolecules in sub-femtoliter volumes.

Electrochemistry↗

PubMed2005

DNA translocation in inorganic nanotubes.

Inorganic nanotubes were successfully integrated with microfluidic systems to create nanofluidic devices for single DNA molecule sensing. Inorganic nanotubes are unique in their high aspect ratio and exhibit translocation characteristics in which the DNA is fully stretched. Transient changes of ionic current indicate DNA translocation events. A transition from current decrease to current enhancement during translocation was observed on changing the buffer concentration, suggesting interplay between electrostatic charge and geometric blockage effects. These inorganic nanotube nanofluidic devices represent a new platform for the study of single biomolecule translocation with the potential for integration into nanofluidic circuits.

DNA↗

PubMed2005

Thermal conductance and thermopower of an individual single-wall carbon nanotube.

We have observed experimentally that the thermal conductance of a 2.76-microm-long individual suspended single-wall carbon nanotube (SWCNT) was very close to the calculated ballistic thermal conductance of a 1-nm-diameter SWCNT without showing signatures of phonon-phonon Umklapp scattering for temperatures between 110 and 300 K. Although the observed thermopower of the SWCNT can be attributed to a linear diffusion contribution and a constant phonon drag effect, there could be an additional contact effect.

Journal Article↗

PubMed2005

Mathematical model for characterizing noise transmission into finite cylindrical structures.

This work presents a theoretical study of the sound transmission into a finite cylinder under coupled structural and acoustic vibration. Particular attention of this study is focused on evaluating a dimensionless quantity, "noise reduction," for characterizing noise transmission into a small cylindrical enclosure. An analytical expression of the exterior sound pressure resulting from an oblique plane wave impinging upon the cylindrical shell is first presented, which is approximated from the exterior sound pressure for an infinite cylindrical structure. Next, the analytical solution of the interior sound pressure is computed using modal-interaction theory for the coupled structural acoustic system. These results are then used to derive the analytical formula for the noise reduction. Finally, the model is used to predict and characterize the sound transmission into a ChamberCore cylindrical structure, and the results are compared with experimental data. The effects of incidence angle and internal acoustic damping on the sound transmission into the cylinder are also parametrically studied.

Journal Article↗

PubMed2005

[Dynamic three-dimensional reconstruction of tissue Doppler ultrasound heart images].

Traditional 3D ultrasound reconstruction system can just depict 3D anatomical structure, so it is very difficult to give an accurate assessment of the functionality of the heart. In this study, a dynamic 3D reconstruction method of tissue Doppler ultrasound heart images is set up based on the combination of 3D reconstruction and tissue Doppler imaging technique. Dynamic 3D acceleration field of heart movement is reconstructed to supply a new approach of accurate assessment of functionality of the heart. The key problem of vector interpolation and fusion imaging in the process of acceleration vector field reconstruction is solved. The 3D acceleration field of heart movement and anatomical structure is reconstructed separately from the original tissue Doppler acceleration images and showed in the same field. The experimental results testified that the 3D space relationship of acceleration and anatomical structure is correct and this method can supply more information for the assessment of heart functionality.

Echocardiography, Doppler↗

PubMed2005

[Estimation of fetal weight on the basis of neural network].

The ultrasonic estimation of fetal weight at delivery is of important prognostic significance in obstetrical practice. The convertional regression formulas used for estimating fetal weight have the disadvantage of less reliability. In this study, we used the back propagation neural network (BP) to estimate Fetal Weight. Some input variables were adopted in constructing the BP model: biparietal diameter (BPD), cerebellum transverse diameter (TCD), abdominal circumference (AC), liver length (LL), femur length (FL), fetal thigh soft tissue thickness (FSTT), and gestational age (GA). The fetal weights of 109 singleton fetuses were estimated. In the training group and validation group, coincidence rates were 89.77% and 76.19% respectively. The results show that the estimation based on neural network is more accurate than that by regression method. GA, its unit is not week but day in our formulas, is very valuable in combination with other ultrasonic parameters on estimation.

Anthropometry↗

PubMed2005

[Recommendations for mitral regurgtitation with Doppler echocardiography].

Mitral regurgitation is one of the most serious heart diseases. With the development of up-to-date medical techniques, the ratio of successful operations in valvular repair and valvular replacement has been largely improved. Examinations before operation become extremely crucial. Accurate method is required in assessing the degree of mitral regurgitation to set down the corresponding treatment method. This paper reviews the evaluation methods of mitral valvular regurgitation provided in these years and presents comments on the application areas as well as the merits and disadvantages of those methods. Finally, the prospect of the method based on three-dimensional Doppler ultrasonographic imaging on mitral regurgitation is discussed.

Echocardiography, Doppler, Color↗

PubMed2004

Thermal expansion and impurity effects on lattice thermal conductivity of solid argon.

Thermal expansion and impurity effects on the lattice thermal conductivity of solid argon have been investigated with equilibrium molecular dynamics simulation. Thermal conductivity is simulated over the temperature range of 20-80 K. Thermal expansion effects, which strongly reduce thermal conductivity, are incorporated into the simulations using experimentally measured lattice constants of solid argon at different temperatures. It is found that the experimentally measured deviations from a T(-1) high-temperature dependence in thermal conductivity can be quantitatively attributed to thermal expansion effects. Phonon scattering on defects also contributes to the deviations. Comparison of simulation results on argon lattices with vacancy and impurity defects to those predicted from the theoretical models of Klemens and Ashegi et al. demonstrates that phonon scattering on impurities due to lattice strain is stronger than that due to differences in mass between the defect and the surrounding matrix. In addition, the results indicate the utility of molecular dynamics simulation for determining parameters in theoretical impurity scattering models under a wide range of conditions. It is also confirmed from the simulation results that thermal conductivity is not sensitive to the impurity concentration at high temperatures.

Journal Article↗

PubMed2004

[Axis registration and image interpolation of rotary scanning echocardiogram].

The object of this study was to work at accurate axis registration and interpolation methods for multi-dimension reconstruction of rotary scanning ultrasonic medical images. At first, time-field curves of the images' axes were analyzed according to their characteristic points and the axial direction registration was realized. Similar matrix was used to find registration pixels line near the axes of two images. Auto-correlation function and Fourier spectrum were used to evaluate the effects of axes registration. Second, an interpolation method was studied for the special space distribution of rotary scanning images. Results of experiments indicate that the axes registration and interpolation methods were suitable to rotary scanning medical images. The quality of reconstruction can be greatly improved by registration-based interpolation methods.

Algorithms↗