Biomedical subjects

L Sheng

Publications and source records attributed to L Sheng.

At least 19 recordsLinked to original sources

PubMed2006

Quantum spin-Hall effect and topologically invariant Chern numbers.

We present a topological description of the quantum spin-Hall effect (QSHE) in a two-dimensional electron system on a honeycomb lattice with both intrinsic and Rashba spin-orbit couplings. We show that the topology of the band insulator can be characterized by a 2 x 2 matrix of first Chern integers. The nontrivial QSHE phase is identified by the nonzero diagonal matrix elements of the Chern number matrix (CNM). A spin Chern number is derived from the CNM, which is conserved in the presence of finite disorder scattering and spin nonconserving Rashba coupling. By using the Laughlin gedanken experiment, we numerically calculate the spin polarization and spin transfer rate of the conducting edge states and determine a phase diagram for the QSHE.

Journal Article↗

PubMed2006

Theory of the phonon Hall effect in paramagnetic dielectrics.

Based upon Raman spin-lattice interaction, we propose a theoretical model for the phonon Hall effect in paramagnetic dielectrics, which was discovered recently in an experiment [C. Strohm, G. L. J. A. Rikken, and P. Wyder, Phys. Rev. Lett. 95, 155901 (2005).]. The phonon Hall effect is revealed to be a phonon analogue to the anomalous Hall effect in electron systems. The thermal Hall conductivity is calculated by using the Kubo formula. Our theory reproduces the essential experimental features of the phonon Hall effect, including the sign, magnitude, and linear magnetic field dependence of the thermal Hall conductivity.

Journal Article↗

PubMed2006

Biological activity of residual cell-substrate DNA.

Vaccines and other biological products manufactured in cells contain contaminating residual DNA derived from that production cell substrate, with the amount and form of this DNA depending mainly on the type of vaccine. The potential risk of this cellular DNA has been debated for over 40 years without resolution. Opinions on residual DNA have varied from it being considered an inert contaminant, and thus its presence should not be deemed to be a risk to vaccine recipients, to it being considered an important risk factor, particularly for vaccines manufactured in certain cell substrates, such as cells derived from tumours or cells that are tumorigenic. We are not of the opinion that DNA can be considered biologically inert, but whether or what risk residual cell-substrate DNA poses remains to be determined. In this paper, we discuss our approaches to address this issue and describe some preliminary work.

Carcinogens↗

PubMed2005

Nondissipative spin Hall effect via quantized edge transport.

The spin Hall effect in a two-dimensional electron system on honeycomb lattice with both intrinsic and Rashba spin-orbit couplings is studied numerically. Integer quantized spin Hall conductance is obtained at the zero Rashba coupling limit when electron Fermi energy lies in the energy gap created by the intrinsic spin-orbit coupling, in agreement with recent theoretical prediction. While nonzero Rashba coupling destroys electron spin conservation, the spin Hall conductance is found to remain near the quantized value, being insensitive to disorder scattering, until the energy gap collapses with increasing the Rashba coupling. We further show that the charge transport through counterpropagating spin-polarized edge channels is well quantized, which is associated with a topological invariant of the system.

Journal Article↗

PubMed2005

Spin-Hall effect in two-dimensional electron systems with Rashba spin-orbit coupling and disorder.

Using the four-terminal Landauer-Bu ttiker formula and Green's function approach, we calculate numerically the spin-Hall conductance in a two-dimensional junction system with the Rashba spin-orbit (SO) coupling and disorder. We find that the spin-Hall conductance can be much greater or smaller than the universal value e/8pi, depending on the magnitude of the SO coupling, the electron Fermi energy, and the disorder strength. The spin-Hall conductance does not vanish with increasing sample size for a wide range of disorder strength. Our numerical calculation reveals that a nonzero SO coupling can induce electron delocalization for disorder strength smaller than a critical value, and the nonvanishing spin-Hall effect appears mainly in the metallic regime.

Journal Article↗

PubMed2004

Premenstrual syndrome as a predictor of menopausal symptoms.

OBJECTIVE: To estimate whether premenstrual syndrome (PMS) predicts common menopausal symptoms assessed longitudinally for 5 years among women in the transition to menopause. METHODS: Data were obtained from a structured interview questionnaire, daily symptom ratings, and standard measures of depressive symptoms and sleep quality at 7 assessment periods in a population-based cohort of 436 women. Menstrual status was determined by menstrual bleeding dates. Hormones were measured in the early follicular phase, with a maximum of 14 measures per subject. Multivariate logistic regression models for repeated measures were used to estimate the effects of study variables. RESULTS: Premenstrual syndrome significantly decreased with age (P <.001) and with changes in menstrual bleeding status (P =.003). Women with PMS at enrollment were more likely over the 5-year period to report menopausal hot flushes (odds ratio [OR] 2.09; confidence interval [CI] 1.42, 3.08; P <.001); depressed mood (OR 2.34; CI 1.60. 3.43; P <.001); poor sleep (OR 1.72; CI 1.16, 2.53; P =.007), and decreased libido (OR 1.54; CI 1.06, 2.24; P =.024) after adjusting for age, race, diagnosis of major depression, and estradiol. Subjects' fluctuations in estradiol were significantly associated with hot flushes, depressive symptoms, and poor sleep. CONCLUSION: Premenstrual syndrome decreased in the transition to menopause. Women who reported PMS at baseline were at greater risk of menopausal hot flushes, depressed mood, poor sleep, and decreased libido. Further studies of the associations of symptoms and changes in ovarian function are needed to elucidate the underlying symptom physiology and aid in the development of effective treatments for women during the menopausal transition.

Adult↗

PubMed2001

Changes of serum selenium in pregnant women with gestational diabetes mellitus.

Gestational diabetes is one of the most common diseases in pregnancy. In the present work, the possible relationship between serum selenium concentration and gestational diabetes was investigated. Blood samples of 234 pregnant women were collected, including 98 subjects with impaired glucose tolerance (IGT), 46 subjects with gestational diabetes mellitus (GDM), and 90 normal pregnant women (NPW). An additional 17 samples of normal women of fertile age (NW) were collected for comparison. The hydride generation atomic fluorescence spectrometry was used for selenium determination. The mean serum selenium levels obtained for each group were 0.0741 +/- 0.0167 mg/L for NPW, 0.0631 +/- 0.0132 mg/L for IGT, 0.0635 +/- 0.0120 mg/L for GDM, and 0.108 +/- 0.0170 mg/L for NW. Serum selenium levels were significantly lower in pregnant woman with IGT (p < 0.001) and GDM (p < 0.001) than in NPW. Furthermore, an inverse correlation between the serum selenium concentration and the gestational period was also observed. Selenium supplementation during gestation for pregnant women, especially with IGT and GDM, should be considered.

Adult↗

PubMed2001

[Community characteristics of benthonic animals and its relationship to environmental factors in the Nanhu Lake, Changchun].

There are only 21 species of benthonic animals in the Nanhu Lake, Changchun. The dominant species in the benthos community are obvious, and the individual quantity of Limnodrilus hoffmeisteri, Branchiura sowerbyi, and Tendipus plumosus accounts for 87% of the total individual quantity of all benthonic animals. It indicates that the water in the Nanhu Lake is suffering serious organic pollution, and belongs to an eutrophic lake. The peak values of benthos biomass and energy are found in July(48.23 g WW.m-2 and 241.16 kJ.m-2 respectively), while the maximum individual quantity is appeared in May(401 ind.m-2). The distribution of Oligochaeta and aquatic insects has a significant positive correlation to organic content in the sediment(alpha < 0.05). The community structure of benthonic animals reflects adequately the feature of the Nanhu Lake as an eutrophic lake in temperate zone.

Animals↗

PubMed2001

[Spatial pattern and temporal dynamics of Atylotus pallitarsis population in Songnen Plain].

The spatial pattern and its time series dynamics of Atylotus pallitarsis population were examined in this paper. The results showed that the amount of this population was closely related to temperature and humidity, and its blood peak time appeared at about 14:00 o'clock in the afternoon. The population cattle was aggregated distribution and emigration throughout the day, the aggregated distribution pattern was loose mass community, the distribution of insects in the community was at random.

Animals↗

PubMed2001

[Ecological engineering for eutrophication control in lake].

An ecological engineering was conducted for eutrophication control in the Nanhu Lake of Changchun. In 1996, the removal of phosphorus by harvesting aquatic macrophytes and fishes was 149.6 kg and 189.9 kg, respectively, and the phosphorus fixed in molluscs was 153.4 kg. The total output was 492.9 kg, which amounted approximately to the annual phosphorus input to the lake. After ecological engineering, the water quality turned better, the TP concentration in lake water decreased, the phytoplankton density reduced, and the number of phytoplankton species increased. The roles of molluscs and fish in controlling lake eutrophication should be further studied. Ecological engineering is an ideal method to control the eutrophication of urban lakes.

Animals↗

PubMed1999

Affinity capillary electrophoresis coupled with on-line microdialysis by attachable electrode.

This paper developed a new affinity capillary electrophoresis method coupled with on-line microdialysis using attachable electrodes in order to study the interaction of biomacromolecules with their small molecule ligands in the desired physiological conditions. The sampling mechanism was discussed and the experimental conditions were optimized. The affinity constant of sulfamethoxazole (SMZ) with bovine serum albumin (BSA) was determined with homemade equipment. The method is simple and practical.

Calibration↗

PubMed1998

Hepatitis G virus infection in acute fulminant hepatitis: prevalence of HGV infection and sequence analysis of a specific viral strain.

Hepatitis G virus (HGV) is a recently discovered RNA virus, which belongs to the Flaviviridae family. Although HGV infection is usually not associated with elevated serum transaminases, some recent studies have reported that HGV infection is found in a significant number of patients with fulminant hepatitis and may play a role in its etiopathogenesis. In this study the prevalence of HGV infection was determined in 500 healthy blood donors and in 24 patients admitted to hospital because of acute liver failure caused by fulminant hepatitis. The presence of HGV RNA was tested in sera, obtained at admission and before any transfusion was given, by a sensitive seminested reverse transcriptase-polymerase chain reaction (RT-PCR) assay specific for detection of the non-structural (NS)5 region. Nine of the 500 blood donors (1.8%) and two of the 24 patients (8.3%) were found to be HGV RNA positive. One patient was co-infected with HCV and was known to be an intravenous (i.v.) drug user. After intensive supporting treatment, this patient recovered completely. The second patient had no serological markers of known viral hepatitis infection, including hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus (HCV), cytomegalovirus (CMV), Epstein-Barr virus (EBV) and herpes simplex virus (HSV). This patient was successfully transplanted. From both patients, from HGV RNA-positive healthy blood donors and from other patients coinfected with HCV, a part of the HGV NS3 region (nucleotides 4191-4345, EMBL entry U45966) was cloned and sequenced. Sequence comparison revealed that the NS3 region of HGV in patients with fulminant hepatitis contained three nucleotide substitutions as part of the six substitutions described in previous work. These nucleotide substitutions were not found in the tested blood donors or in patients with HCV co-infection. Our findings therefore support the concept of the association of fulminant hepatitis with infection of a specific HGV strain.

Adolescent↗

PubMed1998

High prevalence of hepatitis G virus infection compared with hepatitis C virus infection in patients undergoing chronic hemodialysis.

A recently discovered non-A-E hepatitis virus has been designated as hepatitis G virus (HGV) and identified as a new member of the Flaviviridae family. Infection by this virus is thought to be associated with blood-borne hepatitis and usually in the presence of hepatitis C or hepatitis B virus (HBV) infection. In this study, the presence of HGV-RNA in serum or plasma and the prevalence of antibodies against an HGV envelope protein (E2) were investigated in patients undergoing chronic hemodialysis using a sensitive reverse-transcriptase polymerase chain reaction and an enzyme-linked immunosorbent assay, respectively. HGV-RNA was detected in 19 of 112 patients investigated (17%) and anti-E2 antibodies were detected in 15 of 106 patients studied (14.2%). With the exception of two patients, the appearance of anti-E2 is associated with the clearance of serum HGV-RNA. The total prevalence of current (HGV-RNA positivity) and/or past (anti-E2 positivity) HGV infection in this patient population is thus 28.6% (32 of 112 patients were positive for serum HGV-RNA and/or anti-E2 antibodies). In apparently healthy blood donors, serum HGV-RNA was detected in four of 358 individuals (1.12%) and anti-E2 was not detected in 50 individuals investigated. From the 19 patients with serum HGV-RNA positivity, nine were coinfected with other hepatitis viruses (seven with HBV; one with HBV, hepatitis C virus [HCV], and hepatitis D virus; and one with HBV and cytomegalovirus). Thirteen of 15 patients with anti-E2 positivity (10 were positive for only anti-E2 and three were also positive for anti-HBc) had no detectable HGV-RNA. In two patients, both HGV-RNA and anti-E2 antibodies were concomitantly present (both patients were coinfected with HCV or HBV). Of the HGV-infected patients, only three who were coinfected with HBV showed elevated serum alanine aminotransferase levels. The serum HCV-RNA and/or anti-HCV were detected in five (4.5%) of 112 patients. From these findings, we conclude that there is a high prevalence of HGV infection (28.6%) compared with HCV (4.5%) in patients undergoing hemodialysis in our hospital. However, approximately 50% of patients had spontaneously lost the viremia and developed anti-HGV-E2 antibodies. We confirm that HGV infection alone is not associated with elevated serum transaminases, and the appearance of anti-HGV-E2 is usually accompanied with clearance of serum HGV-RNA. In contrast to the results of our previous study, the majority of patients infected with HGV are not coinfected with HCV, indicating that HGV is capable of independent transmission. It is likely that there is a preferential HGV acquisition in the hemodialysis unit. The clinical significance of long-term infection with HGV remains to be established.

Adult↗

PubMed1998

[Determination of oligopeptide by IR matrix-assisted laser desorption ionization mass spectrometry].

Luteinizing releasing hormone analog (LRH-A), renin substrate tetradecapeptide and angiotensin I were analyzed with infrared-matrix assisted laser desorption ionization/Fourier transform ion cyclotron resonance mass spectrometry (IR-MALDI/FTICR MS). 2,5-Dihydroxybenzoic (DHB) and succinic acid (SA) were used as matrices. The m/z of oligopeptides were determined with an error less than 4 x 10(-6). A series of characteristic fragment ions of peptides were obtained by increasing the laser power density appropriately. Their elemental compositions and the first order structures were confirmed. A sensitive, rapid and accurate method was established for the determination of oligopeptide.

Amino Acid Sequence↗

PubMed1998

Anti-hepatitis G E2 antibody detection and its relation to serum HGV-RNA in patients with clotting disorders: high prevalence of HGV infection and spontaneous remission.

In a previous study, we have determined the prevalence of serum HGV-RNA in patients with congenital clotting disorders. Twenty-six (15%) of 175 patients investigated were serum HGV-RNA positive. In addition, HGV-RNA was detectable in peripheral blood mononuclear cells (PBMC) in ten percent of the cases, three of these patients were serum HGV-RNA negative. In the present study, we have determined the prevalence of anti-HGV-E2 antibodies in the same patient population. Anti-HGV-E2 as determined by ELISA was detected in 45 patients (25.7%). Forty of these patients were serum HGV-RNA negative. Ninety-two percent of the 26 HGV viremic patients and all but one patient (44 patients) with detectable anti-HGV-E2 had coinfection with the hepatitis C virus (HCV). Of these coinfected patients, 62.5% of HGV viremic patients and 53% of anti-HGV-E2 positive patients showed elevated serum ALT levels. Anti-HGV-E2 seroconversion is thus not associated with HCV infection. Two patients who were solely infected with HGV had normal serum ALT levels. In a retrospective longitudinal study, we have observed in 15 patients that serum HGV-RNA persisted during one to 19 years of follow-up, while anti-HGV-E2 was repeatedly negative. Five additional patients who were anti-HGV-E2 positive with concomitant detectable HGV-RNA (4 patients in serum and 1 patient in PBMC) became HGV-RNA negative during follow-up, ranging from 1 to 8 years after the first detection of anti-HGV-E2 antibodies. Two patients had lost anti-HGV-E2 antibodies 3 to 6 years after the seroconversion without the re-appearance of serum HGV-RNA. From these findings, it is clear that the prevalence rate of HGV infection in patients with clotting disorders as determined by PCR assay for HGV-RNA and anti-HGV-E2 by ELISA is actually higher than the prevalence of HGV viremia. Although HGV viremia may persist for longer than 19 years, most of the patients infected with HGV may clear the viremia spontaneously. The clearance of viremia is usually associated with seroconversion to anti-HGV-E2. In addition, anti-HGV-E2 may be lost during years of follow-up without the reappearance of the HGV-RNA. Although HGV infection does not seem to influence the fate of HCV infection and does not induce increased levels of serum ALT, the clinical significance of long-term infection remains to be established.

Adolescent↗

PubMed1997

[Influences of terraazaindene on absorption spec tra and fluorescence spectra of sensitizing dyes].

This study is about the influences of tetraazaindene (TAI) on absorption spectra and the fluorescence spectra of three kinds of sensitizing dyes. The absorption of all peaks of the dyes enhance with increasing TAI, among which the absorption of J-aggregate has even marked enhancement. At certain value of TAI, the absorption of monomolecule of dye enhances much more rapidly as well as the absorption of H-aggegte decreasing because of H-aggregate dissociating into monomolecules. The results obtained also show that the fluorescence emissions of the dyes enhance with increasing TAI. The mechnisms of the observed phenomena are discussed in detail.

English Abstract↗

PubMed1997

Hepatitis G viral RNA in serum and in peripheral blood mononuclear cells and its relation to HCV-RNA in patients with clotting disorders.

The hepatitis G virus (HGV) has recently been identified as a new member of the Flaviviridae family. Infection by this virus is thought to be associated with blood borne hepatitis. In this study, the presence of HCV- and HGV-RNAs in serum or plasma (175 patients) and in peripheral blood mononuclear cells (PBMC) (133 patients) was investigated in patients with clotting disorders using a sensitive reverse transcriptase polymerase chain reaction (RT-PCR). HGV-RNA was detected in serum of 26 patients (14.8%). In apparently healthy blood donors, serum HGV-RNA was detected in 4 of 358 individuals investigated (1.12%). Ninety two percent of the 26 serum HGV-RNA positive patients had coinfection with the hepatitis C virus (HCV), especially with HCV genotype 1b, the most common genotype in Belgium. Of these coinfected patients, 15 (62.5%) showed elevated serum ALT levels. Two patients who were solely infected with HGV had normal serum ALT.HGV-RNA in PBMC was found in 18 patients, of whom 3 were negative for serum HGV-RNA. As in case of HCV, HGV-RNA in PBMC is preferentially sensitive to interferon treatment. Nevertheless, rapid reappearance of HGV-RNA in PBMC was observed after cessation of treatment. In one patient, persistent serum ALT elevation seems to be associated with continued HGV viremia, despite the disappearance of serum HCV-RNA.

Adolescent↗

PubMed1997

[The effect of climatic factors on the onset of acute myocardial infarction].

The results of the single-relative analysis on the three climatic factors of air temperature, pressure and relative humidity to the attack of acute myocardial infarction in Shenyang city located in the cold Northeastern China area, showed that the attack was more frequent in summer time with high temperature, humidity and low air pressure. The attack was positively related to temperature (r = 0.7463 P < 0.01) and humidity (r = 0.6466 P < 0.01) while is negatively related to air pressure (r = -0.7300 P < 0.05). And specifically, in Shenyang area the incidence was obviously increased with average temperature > 20 degrees C, air pressure < 1010, and relative humidity > 70%. Patients should reduce the activities in high or low temperature environment. Proper precautions should be taken well in advance to avoid the attack on the patients in a particular season. And different nursing measures should be taken in different seasons to comply with changes of climate, for averting the attacks caused by the climate.

Aged↗