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Liang Xu

Publications and source records attributed to Liang Xu.

At least 55 records · Page 3Linked to original sources
PubMed2006

[The study of infrared background radiation of earth and atmosphere by airborne FTIR spectrometer].

The present article describes the experiment of airborne Fourier transform infrared (FTIR) spectrometer detecting the background radiation of earth and atmosphere. Considering the surface radiation and atmospheric absorbance and emission, the expression of radiations measured by airborne FTIR is given. It is indicated that the background radiations depend on four parameters: surface temperature, surface emissivity, atmospheric transmission and temperature. Based on theoretic analysis the measured spectra are compared and analyzed according to the differences in altitude and surface. Spectral characters of infrared background radiation are described.

English Abstract↗
PubMed2006

[Application of MALT-CLS method to FTIR quantitative analysis of atmospheric trace gas].

The MALT-CLS method for quantitative analysis of atmosphere trace gas by FTIR spectrometry was studied. Some experiments are described, such as long-path White cell, and passive remote sensing of aircraft. The characteristic of this method is that the calibration spectra are calculated from a database of absorption line parameters HITRAN using MALT program, including environmental and instrumental effects in the calculation. It is particularly useful in long open-path and solar FTIR spectroscopy, or passive remote sensing by FTIR.

English Abstract↗
PubMed2005

Frequency of under-corrected refractive errors in elderly Chinese in Beijing.

PURPOSE: The aim of the study was to evaluate the prevalence of under-corrected refractive error among elderly Chinese in the Beijing area. METHODS: The population-based, cross-sectional, cohort study comprised 4,439 subjects out of 5,324 subjects asked to participate (response rate 83.4%) with an age of 40+ years. It was divided into a rural part [1,973 (44.4%) subjects] and an urban part [2,466 (55.6%) subjects]. Habitual and best-corrected visual acuity was measured. Under-corrected refractive error was defined as an improvement in visual acuity of the better eye of at least two lines with best possible refractive correction. RESULTS: The rate of under-corrected refractive error was 19.4% (95% confidence interval, 18.2, 20.6). In a multiple regression analysis, prevalence and size of under-corrected refractive error in the better eye was significantly associated with lower level of education (P<0.001), female gender (P<0.001), and age (P=0.001). CONCLUSIONS: Under-correction of refractive error is relatively common among elderly Chinese in the Beijing area when compared with data from other populations.

Adult↗
PubMed2005

Solid phase microextraction for analysis of alkanes and aromatic hydrocarbons in human breath.

In this work, solid phase microextraction-gas chromatograph (SPME-GC) was applied to analyze alkanes and aromatic hydrocarbons in human breath, providing a potential non-invasive method to screen lung cancer. This method has been optimized and evaluated. It provided quantification limits ranging from 0.04 to 4.2 ng/mL, linear correlations ranging from 0.9845 to 0.9966 and R.S.D. values less than 9.8%. Total 30 breath samples, from 15 lung cancer patients and 15 healthy persons, were analyzed, and the alkanes and aromatic hydrocarbons were detected in 73.3% lung cancer patients and in 13.3% healthy persons by this method. Above all, It was demonstrated that this SPME-GC method provided a sensitive and non-invasive measure means to analyze alkanes and aromatic hydrocarbons in human breath, and brought forward a potential application for screening lung cancer.

Aged↗
PubMed2005

Intraocular pressure in Northern China in an urban and rural population: the Beijing eye study.

PURPOSE: To evaluate intraocular pressure (IOP) and its demographic associations in an urban and rural population in Northern China. DESIGN: Population-based cohort study. METHODS: In the Beijing Eye Study, IOP was measured by noncontact pneumatonometry. Mean age was 56.20 +/- 10.59 years (range, 40-101 years). RESULTS: Mean IOP was 16.11 +/- 3.39 mm Hg (median, 16 mm Hg; range, 7-60 mm Hg). In the rural group and the urban population group, respectively, IOP was significantly (P = .016 and P = .029, respectively) lower in the high-age group (>or=75 years) than in the middle-age group (55-64 years). In the rural group, IOP was additionally significantly lower in the age group of 40 to 44 years than in the middle-age group, which suggests a reversed U-like course. A multiple regression analysis revealed that IOP significantly increased with myopia (P = .024), and that it was statistically independent of rural area vs urban area (P = .12) and gender (P = .71). CONCLUSION: In the Northern Chinese population, mean and median of IOP that is measured by pneumatonometry is 16 mm Hg with a normal range (mean +/- two SDs) of 10 to 22 mm Hg. In cross-sectional analysis, IOP slightly increased towards an age of 55 to 64 years and decreased towards higher ages. IOP increased with myopia. It was not associated with rural vs urban region or gender.

Adult↗
PubMed2005

Refractive error in urban and rural adult Chinese in Beijing.

PURPOSE: To evaluate refractive error and its demographic associations in an urban and rural population in northern China. DESIGN: Epidemiological study. PARTICIPANTS: The Beijing Eye Study is a population-based cohort study in northern China including 4439 subjects. Excluding pseudophakic and aphakic patients, the present study involved 4319 subjects. It was divided into a rural part (1905 [44.1%] subjects) and an urban part (2414 [55.9%] subjects). Mean age was 55.85+/-10.33 years (range, 40-90). METHODS: Standardized ophthalmologic examination. For statistical analysis, the spherical equivalent was converted to binary variables, and logistic regression was used to investigate the association with continuous or categorical independent variables. MAIN OUTCOME MEASURE: Refractive error. RESULTS: Mean refractive error measured -0.33+/-2.22 diopters (D) (range, -20.88 to +7.88). Myopia of >-0.50 D, -1.0 D, >-6.0 D, and >-8 D, respectively, occurred in 22.9% (95% confidence interval [CI], 21.7-24.2), 16.9% (95% CI, 15.8-18.0), 2.6% (95% CI, 2.2-3.1), and 1.5% (95% CI, 1.1-1.9) of the subjects, respectively. Myopic refractive error was associated significantly with younger age (P<0.001), urban region (vs. rural region) (P<0.001), higher educational background (P<0.001), higher degree of nuclear cataract (P<0.001), decreasing uncorrected visual acuity (UCVA) (P<0.001), decreasing best-corrected visual acuity (BCVA) (P<0.001), and female gender (P<0.001). Prevalence of high myopia (myopic refractive error >-8 D) was associated with age (P<0.001), female gender (P = 0.020), urban region (P = 0.023), and lower BCVA (P<0.001). Mean anisometropia was 1.09+/-2.03 D (median, 0.38; range, 0-22.0). Prevalence of anisometropia of > or =1 D was associated significantly with age (P<0.001), refractive error (P<0.001), BCVA (P<0.001), and region (P<0.001). Mean astigmatic error measured 0.62+/-0.90 D (median, 0.25; range, 0-7.50). Astigmatism of > or =1 D was associated significantly with age (P<0.001), lower UCVA (P = 0.003), lower BCVA (P<0.001), urban area (P<0.001), and degree of cortical cataract (P = 0.027). CONCLUSIONS: As in other population-based studies on Chinese, myopia was more prevalent in younger subjects. Myopia was associated with urban region, educational background, female gender, decreasing visual acuity, and nuclear cataract. If longitudinal studies confirm the association of refractive error with age, refractive surgery may achieve emmetropia only for a limited time.

Adult↗
PubMed2005

(-)-Gossypol enhances response to radiation therapy and results in tumor regression of human prostate cancer.

Radioresistance markedly impairs the efficacy of tumor radiotherapy and involves antiapoptotic signal transduction pathways that prevent radiation-induced cell death. The majority of human prostate cancers overexpress the important antiapoptotic proteins Bcl-2 and/or Bcl-xL, which render tumors resistant to radiation therapy. (-)-Gossypol, a natural polyphenol product from cottonseed, has recently been identified as a potent small molecule inhibitor of both Bcl-2 and Bcl-xL. In the current study, we investigated the antitumor activity of (-)-gossypol in prostate cancer and tested our hypothesis that (-)-gossypol may improve prostate cancer's response to radiation by potentiating radiation-induced apoptosis and thus making cancer cells more sensitive to ionizing radiation. Our data show that (-)-gossypol potently enhanced radiation-induced apoptosis and growth inhibition of human prostate cancer PC-3 cells, which have a high level of Bcl-2/Bcl-xL proteins. Our in vivo studies using PC-3 xenograft models in nude mice show that orally given (-)-gossypol significantly enhanced the antitumor activity of X-ray irradiation, leading to tumor regression in the combination therapy. In situ terminal deoxynucleotidyl transferase-mediated nick end labeling staining showed that significantly more apoptotic cells were induced in the tumors treated with (-)-gossypol plus radiation than either treatment alone. Anti-CD31 immunohistochemical staining indicates that (-)-gossypol plus radiation significantly inhibited tumor angiogenesis. Our results show that the natural polyphenol inhibitor of Bcl-2/Bcl-xL, (-)-gossypol, can radiosensitize prostate cancer in vitro and in vivo without augmenting toxicity. (-)-Gossypol may improve the outcome of current prostate cancer radiotherapy and represents a promising novel anticancer regime for molecular targeted therapy of hormone-refractory prostate cancer with Bcl-2/Bcl-xL overexpression.

Animals↗
PubMed2005

[The prevalence and its effective factors of primary angle-closure glaucoma in defined populations of rural and urban in Beijing].

OBJECTIVE: To investigate the prevalence of primary angle-closure glaucoma (PACG) of urban and rural residents in Beijing, China. A quantitative comparison was made based on the data collected from this epidemiological survey. We also identify some of the most typical risk factors associated with PACG. METHODS: Glaucomatous screening examination was applied to specific age group populations (aged 40 and older) in the defined district of Beijing and its remote rural county, from June to October, 2001. There are 4451 subjects in all, 1980 rural subjects and 2471 urban subjects, 1939 males and 2512 females. The screen and diagnostic methods used in this survey included van Herick methods and gonioscopy examination to estimate the peripheral depth of the anterior chamber, visual acuity, intraocular pressure, refraction status, stereoscopic fundus photography, and threshold-related visual field tests. Subjects regarded as suspected glaucoma and glaucoma patients are reexamined with standard glaucomatous examination. RESULTS: The response rate of rural and urban population is 79.6% (1980/2488), 87.1% (2471/2836), respectively. The prevalence of PACG (in aged 40 years or older population) resulted from this survey was 1.2% (95% CI 0.9% - 1.5%). However, the prevalence was different between urban and rural residents, 1.1% (95% CI 0.8% - 1.4%) vs. 1.6% (95% CI 1.2% - 2.0%). The prevalence of PACG in female was more than that in male, 1.7% (95% CI 1.3% - 2.1%) vs.0.8% (95% CI 0.5% - 1.1%). A drastic increase in prevalence of PACG with age increase was identified in both survey sites, however, this increase in rural subjects (aged 60-69 years group) occurred ten years earlier than those from urban subjects (aged more than 70 years group). Compared to urban residents, rural residents showed higher prevalence of unilateral low vision (39.3% vs. 20.6%) and blindness (28.6% vs. 14.7%). This survey also confirmed that, as people aging, refraction status became hyperopia, the depth of peripheral anterior chamber became narrow. In the different age groups, female and male groups, the changes of refraction status and the depth of peripheral anterior chamber paralleled the prevalence of PACG. CONCLUSIONS: The prevalence of PACG was obviously different in different groups. This could due to several factors including gender, age, change of refraction status and chamber angle as well.

Adult↗
PubMed2005

[A comparative study of optic nerve damage between primary open angle glaucoma and normal tension glaucoma].

OBJECTIVE: To investigate the differences in the characteristics of optic nerve damage in patients with primary open angle glaucoma (POAG)and normal tension glaucoma (NTG). METHOD: The optic disc parameters and retinal nerve fiber layer (RNFL) of 47 eyes of 39 subjects with POAG (IOP > 24 mmHg) and 38 eyes of 32 subjects with NTG (IOP < 21 mmHg) were measured by using a Heidelberg retina tomograph II, color stereo-optic disc photographs, and an Octopus automated perimetry. RESULTS: (1) Rim area, rim/disc area ratios and three sectors except temporal quadrant of optic disc were significantly smaller, whereas C/D was significantly larger in patients with NTG than those of POAG. The mean RNFL thickness and RNFL cross-sectional areas at temporal/interior and temporal/superior in those with NTG were significantly (P < 0.05) smaller than those of POAG. The rim volume was significantly (P < 0.05) smaller and mean cup depth was significantly (P < 0.05) larger in patients with NTG than POAG. (2) The defect types of RNFL: RNFL diffuse loss and local defect ratio were 53.19% and 4.26% in POAG, respectively; while were 21.05% and 55.26% in NTG, respectively. The difference between the proportions of the defect type of RNFL in patients with POAG and those of NTG is statistically significant (P < 0.01). CONCLUSIONS: Our results demonstrate that the varieties of C/D area ratio, rim area, RNFL thickness, and defect types of RNFL with NTG and POAG indicate that the different mechanisms are involved in optic nerve damage in the two types of glaucoma.

Adult↗
PubMed2005

[Immune tolerance induced by staphylococcal enterotoxin B for the treatment of rat high-risk corneal transplantation rejection].

OBJECTIVE: To determine the mechanism of staphylococcal enterotoxin B (SEB) induced immune tolerance in the treatment of high-risk corneal transplantation in the rat. METHODS: Fisher 344 rats were used as donors and Lewis rats were used as recipients. Corneal neovascularization was induced by sutures. The rats were divided randomly into five groups in a masked fashion. In the 4 SEB-treated groups, 0.2 ml SEB were intraperitoneally injected before the keratoplasty at concentrations of 25 microg/kg, 50 microg/kg, 75 microg/kg and 100 microg/kg, respectively. The control group received a saline buffer injection intraperitoneally. All allografts were observed and scored for 30 days. Meanwhile, the infiltration of lymphocytes in the allografts, the percentage of lymphocyte subpopulations in the immune organs, the proliferation ability of the lymphocytes and the cytokines in the serum were measured. RESULTS: The SEB at the concentration of 25 microg/kg did not prolong the survival time of the allografts as compared to the control group. With the increase of the concentration of SEB, the survival time in the other three SEB-treated groups were prolonged significantly and the 75 microg/kg group showed the best results. The infiltration of the lymphocytes in the allografts and the percentages of CD4+ and CD8+ lymphocytes in the immune organs in the SEB treated groups were reduced. The proliferation ability of the lymphocytes in SEB treated groups was decreased; the concentration of IL-2 was lower while the concentration of IL-10 was higher in the serum in the SEB treated groups. CONCLUSIONS: SEB at an optimal concentration is effective in inhibiting immune rejection in high-risk corneal transplantation. The mechanism of SEB induced immune tolerance is related to the reduction of the number and the immune tolerance status of the lymphocytes.

Animals↗
PubMed2005

[The value of frequency doubling perimetry in glaucoma screening of aged 40 or more population].

OBJECTIVE: To investigate the diagnosis value of the frequency doubling perimetry (FDP) screening program in the aged 40 or more natural population-based glaucoma screening. METHODS: In 3 natural villages of Daxing District and 4 northern metropolitan communities of Beijing, 4439 subjects aged 40 or over were screened for glaucoma from May to October in 2001. The screening protocol C-20-1 of the frequency doubling perimetry (FDP) was used in all subjects. For suspect glaucoma subjects, TOP threshold visual field testing with an Octopus perimeter, gonioscopy and stereo fundusgraphy were performed on different days. Detected Glaucoma patients were classified as mild (MD 5 dB or less), moderate (MD > 5 dB and < 10 dB) and advanced (MD 10 dB or more) degrees according to their Octopus test results. FDP parameters including test time, numbers of abnormal location, comtotalon score and score by quadrant were analyzed. Data from one eye of normal subjects and milder eye of optic nerve damage in glaucoma subjects were analyzed. RESULTS: After excluding subjects whose fixation error or false positive error was > 0.33, data from 4330 subjects (97.54%) were analyzed. If abnormality of one location or more was used as a FDP cutoff, and subjects were divided into normal and glaucoma two groups (excluded other eye diseases in non-glaucoma subjects); the FDP had a sensitivity of 50.70% (72/142), a specificity of 90.58% (2260/2340), an area under the ROC curve (AUC) of 0.74, a positive predictive value (PV) of 47.71%, a negative predictive value of 96.95%, a positive likelihood ratio (LR) of 14.83 and a negative LR of 0.51. If excluded the eyes without glaucomatous optic nerve changes and visual field damage, the FDP had a sensitivity of 76.39%, an AUC of 0.87, a positive PV of 40.74%, a negative PV of 99.25%, a positive LR of 22.34 and a negative LR of 0.24. The sensitivity of detecting mild, moderate and advanced glaucoma was 54.17%, 76.00% and 100.00%, respectively. There was strong negative correlation between FDP quadrant score and quadrant mean sensitivity (MS) of Octopus perimetry in glaucoma patients (Spearman correlation, Rs = -0.732, -0.628, -0.639, -0.679, all P = 0.000). CONCLUSIONS: The FDP screening protocol C-20-1 is a very rapid functional test for screening glaucoma in large natural populations aged 40 or more and is proven to be feasible. It has high specificity and good sensitivity for moderate and advanced glaucoma.

Adult↗
PubMed2005

[Single channel multifocal VEP studies in normal Chinese].

OBJECTIVE: To investigate the waveform characters of single channel mVEP and its variability in normal Chinese people. METHODS: VERIS Science 4.3 system was used to record and analyze single channel mVEP. The stimulation was performed with a 60 pattern segment dartboard configuration. The Michelson contrast was 99% and the repetition rate 75 Hz. Recording electrodes were placed 3 cm above and 3 cm below the inion. The m-14 sequence required 4 minutes of recording time per eye, which was divided into 8 short segments. The signal was amplified 100 000 times and band-pass filtered between 3 and 100 Hz. The first slices of second kernel at 60 locations were analyzed. The main wave peak-to-trough amplitude and latency from 30 to 130 ms signal window were measured and calculated with the costumed Matlab program. The study included 64 normal subjects (39 women and 25 men). The age range was 13 - 66 years. 7 subjects were tested 2 - 7 times on different occasions for reproducibility. The statistic analysis was performed with Excel and SPSS. RESULTS: In mVEP trace array, the polarity of upper hemifield traces was usually opposite to lower hemifield traces. However, at near vertical meridian areas and near below horizontal meridian areas, the trace polarity had some variability. The main wave mean amplitudes of 60 location responses in left eye were from 0.177 microV to 0.401 microV. The amplitude CVs for 60 locations were from 36.6% to 60.7%. The mean latencies of 60 location responses were from 100 to 116 ms, and latency CVs were from 8.8% to 18.1%. The smaller signals located in zones of upper periphery, along vertical meridian, below horizontal meridian and the larger signals located in near horizontal meridian areas and near non-axial meridian areas which distribution is like a bow tie. There was smaller amplitude variability in the some upper hemifiled locations with smaller amplitude, and there was larger amplitude variability in the some lower hemifiled locations with larger amplitude. The mean amplitudes of all 60 locations in male subjects were lower than that in female subjects, in which 30 locations were low significantly (P < 0.05). The gender influence on latency was less, in which only at 10 locations the difference was significant (P < 0.05). At 20 locations of all, which were mainly distributed at near vertical meridian of lower hemifiled, there was a significant positive correlation of age with amplitude. The age influence on latency was also less. CONCLUSIONS: The larger variability of main wave peak-to-trough amplitude in single channel mVEP existed in different subjects and different locations of same subject. In analysis of mVEP amplitude, the influence of VEP curve location, gender and age should be considered. The main wave latencies of intersubject and intrasubject have smaller variability, and less effect by gender and age, so latency may be a useful diagnostic parameter.

Adolescent↗
PubMed2005

[Characteristics of staphylococcal enterotoxin B (SEB)-induced anergy in transplantation of allogeneic bone marrow cells].

AIM: To investigate the characteristics of the SEB-induced anergy in transplantation of allogeneic bone marrow cells. METHODS: C57BL/J (recipients) and BALB/c (donors) mice were used in this study. The recipients were irradiated with 6.0Gy (60)Co-gamma ray followed by transplantation of allogeneic bone marrow cells (6x10(7)). The recipients treated with (60)Co-gamma-ray were then divided into 3 groups; group 1 treated with (60)Co-gamma-ray (RI control group), and group 2 (transplantation control group) and group 3 (SEB experimental group) received saline or 60 mug SEB after the transplantation of bone marrow cells. T cell subtypes and expression of MHC molecules were detected by flow cytometry. Proliferation of lymphocytes in response to ConA and allogeneic antigen were examined by MLR. RESULTS: (1) The recipients treated with and without SEB survived for at least 180 days and became chimeric with white hair color (the donors' color). (2) SEB inhibited proliferation of lymphocytes in the recipients in response to ConA but not to allogeneic antigen as compared with that in the Group 1 and Group 2 mice. (3) The CD4(+) T but not CD8(+) T cells in the recipients treated with SEB were decreased from day 30 to day 60 after transplantation. (4) With the treatment of SEB, frequency of CD3(+)/NK1.1(+) NKT cells was increased to 5.71% on day 180. In the recipients, the expression of donor's MHC H-2K(d) were enhanced 80.95% and of expression self MHC H-2K(b) was 1.45% only. CONCLUSION: SEB can induce a stronger anergy than that induced by irradiation. SEB-induced anergy is related with the reduction of CD4(+) T cells and increase of CD3(+)/NK1.1(+) NKT cells at the early phase of transplantation. T cells showed specific down-regulation in this study.

Animals↗
PubMed2005

Degradation of dyestuff wastewater using visible light in the presence of a novel nano TiO2 catalyst doped with upconversion luminescence agent.

A new upconversion luminescence agent, 40CdF2 x 60BaF2 x 0.8Er2O3, was synthesized and its fluorescent spectra were determined. This upconversion luminescence agent can emit five upconversion fluorescent peaks shown in the fluorescent spectra whose wavelengths are all below 387 nm under the excitation of 488 nm visible light. This upconversion luminescence agent was mixed into nano rutile TiO2 powder by ultrasonic and boiling dispersion and the novel doped nano TiO2 photocatalyst utilizing visible light was firstly prepared. The doped TiO2 powder was charactered by XRD and TEM and its photocatalytic activity was tested through the photocatalytic degradation of methyl orange as a model compound under the visible light irradiation emitted by six three basic color lamps. In order to compare the photocatalytic activities, the same experiment was carried out for undoped TiO2 powder. The degradation ratio of methyl orange in the presence of doped nano TiO2 powder reached 32.5% under visible light irradiation at 20 h which was obviously higher than the corresponding 1.64% in the presence of undoped nano TiO2 powder, which indicate the upconversion luminescence agent prepared as dopant can effectively turn visible lights to ultraviolet lights that are absorbed by nano TiO2 particles to produce the electron-cavity pairs. All the results show that the nano rutile TiO2 powder doped with upconversion luminescence agent is a promising photocatalyst using sunlight for treating the industry dye wastewater in great force.

Azo Compounds↗
PubMed2005

[Application of FTIR spectra fitting method in retrieving gas concentrations].

The method of retrieving gas concentrations by FTIR spectra measurement system is studied. NLLS fitting algorithm is used to complete the quantitative analysis of CO gas under WINDOWS operating system. The spectra of HITRAN database is employed as calibrating and training sets during the procedure of fitting FTIR spectrum. The measured IR transmittance spectra of CO are best fitted with the calculated spectra in HITRAN. The CO concentrations are acquired after the best fitting. The absolute accuracy of the results of retrieve achieves 1%-5%.

English Abstract↗