Biomedical subjects

Yajun Li

Publications and source records attributed to Yajun Li.

13 recordsLinked to original sources

PubMed2006

Expansions for irradiance distribution near the focus in systems of different Fresnel numbers.

It is shown in an earlier paper dealing with flat-topped light beams [Opt. Lett. 27, 1007 (2002)] that the profile of flat-topped beams can be expressed in the form 1-[1-exp(-xi2)]M, where xi is a dimensionless parameter and M is a nonnegative number. The expansion of the proposed expression is a finite series containing only the lowest-order Gaussian modes. This situation provides the possibility of reformulating the scalar theory of diffraction at an aperture in an opaque screen if the Gaussian mode expansion is employed to describe the boundary values of the light incident on the screen. As an example of this effort, an asymptotic model is established for three-dimensional irradiance distributions near the focus in systems of different Fresnel numbers. The proposed expansions contain only elementary functions and permit all elementary operations; therefore no special functions or special algorithms are needed in the evaluation of either irradiance distributions or the integrated energy in a focused field.

Journal Article↗

PubMed2005

Therapeutic mechanism of Saikosaponin-d in anti-Thy1 mAb 1-22-3-induced rat model of glomerulonephritis.

AIMS: Mesangioproliferative glomerulonephritis is a common kidney disease and at present, there is no effective treatment. Our previous studies have demonstrated that Sairei-to can significantly prevent progression of experimental glomerulonephritis in rats. Although we have reported that the active component of Sairei-to in treatment of glomerulonephritis was Saikosaponin-d (Ssd), mechanism of Ssd in prevention of mesangioproliferative glomerulonephritis progression is still unknown. Therefore, current study examines the effects of Ssd on progression of mesangioproliferative glomerulonephritis induced by anti-Thy1 monoclonal antibody 1-22-3 (mAb 1-22-3) in uninephrectomized rats. METHODS: Eighteen female Wistar rats first received uninephrectomy and mAb 1-22-3 injection and were then divided into 3 groups: treated daily with phosphate-buffered saline (PBS), 0.6 or 1.8 mg/kg of Ssd. Urinary protein concentration and systolic blood pressure were evaluated and the kidneys were collected and subjected to histological and immunohistological evaluation. The mRNA and protein of the kidneys were extracted and subjected to reverse transcriptase polymerase chain reaction and Western blot analysis, respectively. RESULTS: Ssd reduced the amount of urinary protein and systolic blood pressure. Ssd administration also decreased extracellular matrix expansion, crescentic formation as well as infiltration of macrophages and CD8+ T lymphocytes. Moreover, Ssd significantly reduced expression of transforming growth factor beta 1 (TGF-beta1) and type I collagen in the kidneys. CONCLUSION: Ssd inhibits the progression of mesangioproliferative glomerulonephritis through reduction of the expression of TGF-beta1 and the infiltration of macrophages and CD8+ T lymphocytes.

Animals↗

PubMed2005

Functionalized polydiacetylene-glycolipid vesicles interacted with Escherichia coli under the TiO2 colloid.

The interaction of the conjugated system between functionalized polydiacetylene-glycolipid vesicles and Escherichia coli was investigated under the bactericidal effect of TiO(2) colloid. With various pre-incubation and irradiation time, controllable bacteria quantity in the presence of TiO(2) colloid was obtained in real time. UV-visible and Raman spectra were utilized to monitor and evaluate the structural transition of bacteria-polydiacetylene-glycolipid vesicles conjugated system under the different conditions, which supplied the detailed information of the transform of the polydiacetylene backbone in real time. Thus controllable conjugated bio-interaction between two bio-interfaces was obtained through the introduction of the third factor and monitored in real time. This would be great aid in fundamental understanding more complex interfaces in the biological environment and would be applicable to the biomedical and biophysical fields.

Acetylene↗

PubMed2005

Focal shifts in diffracted converging electromagnetic waves. I. Kirchhoff theory.

Starting with the vector formulation of the Kirchhoff diffraction theory, expressions for the total energy density distribution along the axis are presented without using any of the usual assumptions except the assumption made by Kirchhoff for the boundary conditions of a black screen. To make the Kirchhoff integral compatible with Maxwell's equations, a line integral around the edge of the aperture is added in the analysis. The consequence of ignoring the contribution of this line integral to the axial field distribution is examined numerically. The focal shift effect is investigated for both aplanatic systems and parabolic mirrors having an arbitrary numerical aperture (NA) and finite value of the Fresnel number. The combined effects of the Fresnel number and NA on the focal shift are evaluated, and the validity of the results is carefully checked by comparing the wavelength with the system dimensions.

Journal Article↗

PubMed2005

Focal shifts in diffracted converging electromagnetic waves. II. Rayleigh theory.

Part II of this study is an application of the Rayleigh vector diffraction integrals to an investigation of the effect of focal shifts in converging spherical waves diffracted in systems of arbitrary relative aperture. The results are compared numerically with those obtained in Part I [J. Opt. Soc. Am. A 22, 68 (2005)] from the Kirchhoff vector diffraction theory. The effect of the numerical aperture (NA) on focal shifts can be considered in two regions: When NA < or = 0.5 the system behaves like an paraxial system, and the Fresnel number is the dominant factor. When 0.5 < NA < or = 0.9 the absolute value of the relative focal shift decreases with increasing value of NA.

Journal Article↗

PubMed2004

A QSAR study on inhibitory activities of 1-phenylbenzimidazoles against the platelet-derived growth factor receptor.

A quantitative structure-activity relationship (QSAR) study on inhibitory activities of 1-phenylbenzimidazoles against the platelet-derived growth factor receptor (PDGFR) was carried out in this work, and a QSAR model was developed. It gives an r2 of 0.78 for the training set of 55 active compounds, and an r2 of 0.75 for the test set of 24 active compounds. The new model was further applied to predict inhibitory activities of additional 44 inactive compounds, and very good agreement with experimental observations was obtained. The new model requires only variable connectivity indices and two position indices as input parameters, which is simple and easy to apply. The new model is useful for developing new anticancer drugs, which also demonstrates that the recently developed variable connectivity indices are very useful structural descriptors in the QSAR studies in the fields of pharmaceutics and biochemistry.

Antineoplastic Agents↗

PubMed2004

Enhanced affinochromism of polydiacetylene monolayer in response to bacteria by incorporating CdS nano-crystallites.

By incorporating bio-specific receptors, such as p-10,12-pentacosadiyne-1-N-(3,6,9-trioxaundecylamide)-alpha-D-mannopyranoside (MPDA), into 10,12-pentacosadiyonic acid (PDA) monolayer, the MPDA/PDA monolayer underwent affinochromatic transition in response to the bacteria binding to the receptor. Here, we described a new method to study the membrane/macromolececular interaction between Escherichia coli (E. coli) and mannose and its relative affinochromism by modifying MPDA/PDA with CdS nano-crystallites (MPDA/PDA-CdS). CdS not only triggered the strong tropism of the bacteria but also reduced the rigidity of the MPDA/PDA backbone, resulting in the enhanced affinochromism. This discovery might be of significance in basic biophysical studies of membrane/macromolececular and designing novel biosensor.

Acetylene↗

PubMed2004

Mannose-Escherichia coli interaction in the presence of metal cations studied in vitro by colorimetric polydiacetylene/glycolipid liposomes.

Supramolecular assemblies of liposomes (vesicles) made of diacetylenic lipids and synthetic mannoside derivative glycolipid receptors were successfully used to mimic the molecular recognition occurring between mannose and Escherichia coli. This specific molecular recognition was translated into visible blue-to-red color transition (biochromism) of the polymerized liposomes, readily quantified by UV-visible spectroscopy. Some transition metal cations (Cd(2+), Ag(+), Cu(2+), Fe(3+), Zn(2+) and Ni(2+)) and alkali earth metal cations (Ca(2+), Mg(2+) and Ba(2+)) were introduced into the system to analyze their effects on specific biochromism. Results showed that the presence of Cd(2+), Ag(+), Ca(2+), Mg(2+) and Ba(2+) enhanced biochromism. A possible enhancement mechanism was proposed in the process of bacterial adhesion to host cells. However, Cu(2+), Fe(3+), Zn(2+) and Ni(2+) exhibited inhibitory effects that cooperated with diacetylene lipid with a carboxylic group and increased the rigidity of the liposomal outer leaflet, blocking changes in the side chain conformation and electrical structure of polydiacetylene polymer during biochromism.

Acetylene↗

PubMed2004

New generalized Bessel-Gaussian beams.

Analytical expressions are derived for a new set of optical beams, in which the radial dependence is described by a sum of Bessel distributions of different orders, modified by a flat-topped Gaussian function expressed in the form 1 - [1 - exp(-xi2)]M, where xi is a dimensionless parameter and M(> or = 1) is a scalar quantity. The flat-topped Gaussian function can be readily expanded into a series of the lowest-order Gaussian modes with different parameters; this situation makes it possible to express the optical beam as a series of conventional Bessel-Gaussian beams of different orders. The propagation features of this new set of optical beams are investigated to reveal how a windowed Bessel beam passes progressively from a smooth Gaussian window toward the hard-edge limit.

Journal Article↗

PubMed2003

Focal shift in small-Fresnel-number focusing systems of different relative aperture.

Axial irradiance distribution arising from the diffraction of a uniform, converging, spherical wave at a circular aperture is studied on the basis of scalar boundary-diffraction wave theory. The combined effects of Fresnel number and angular aperture on the focal shift are evaluated, and the validity of the results is checked against the Kirchhoff boundary conditions.

Journal Article↗

PubMed2002

Electrochemical and Raman studies of the biointeraction between Escherichia coli and mannose in polydiacetylene derivative supported on the self-assembled monolayers of octadecanethiol on a gold electrode.

Here, we describe a new method to study the biointeraction between Escherichia coli and mannose by using supramolecular assemblies composed of polydiacetylene supported on the self-assembled monolayer of octadecanethiol on a gold electrode. These prepared bilayer materials simply are an excellent protosystem to study a range of important sensor-related issues. The experimental results from UV-vis spectroscopy, resonance Raman spectroscopy, and electrochemistry confirm that the specific interactions between E. coli and mannose can cause conformational changes of the polydiacetylene backbone rather than simple nonspecific adsorption. Moreover, the direct electrochemical detection by polydiacetylene supramolecular assemblies not only opens a new path for the use of these membranes in the area of biosensor development but also offers new possibilities for diagnostic applications and screening for binding ligands.

Acetylene↗

PubMed2002

Propagation and focusing of Gaussian beams generated by Gaussian mirror resonators.

The propagation and focusing properties of a class of Gaussian beams generated by optical resonators with Gaussian reflectivity mirrors are investigated. Attention is concentrated on the following two beams in this class: (a) the annular Gaussian beam (the Gaussian doughnut mode) and (b) the flat-topped Gaussian beam. A class of flat-topped Gaussian beams is introduced. All analysis is limited to a coherent superposition scheme of the lowest-order Gaussian modes (TEM00) that have different parameters.

Journal Article↗

PubMedDate not supplied

Primary bilateral adrenal lymphoma: 2 case reports.

Primary adrenal lymphoma is extremely rare. We describe 2 patients who presented with adrenal insufficiency or fever 'of unknown origin. Conventional imaging studies demonstrated bilateral bulky adrenal masses, and whole-body FDG positron emission tomography- computed tomography showed that the masses were the unique manifestation. Pathological diagnosis was non-Hodgkin lymphoma. The present cases indicated that primary adrenal lymphoma should be included in the differential diagnosis of bilateral adrenal masses.

Adrenal Gland Neoplasms↗