AIM: To investigate the effect of nutritional support therapy on severe acute pancreatitis (SAP).METHODS: A total of 96 patients with severe acute pancreatitis were divided randomly into control and treatment groups.T...AIM: To investigate the effect of nutritional support therapy on severe acute pancreatitis (SAP).METHODS: A total of 96 patients with severe acute pancreatitis were divided randomly into control and treatment groups.The former group received total parenteral nutrition (TPN)via central venous infusion, while parenteral nutrition (PN)and enteral nutrition (EN) therapies were applied in different phases for the latter group. The nutrition status, acute phase responses, pancreas lesions, enteric mucosa penetrability and immune functions were monitored.RESULTS: Body weight and prealbumin concentration were increased in treatment group, compared to those in the control group, but albumin concentration did not change significantly.Acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ)scores decreased after 7 d of treatment, whereas the scores of the control group decreased on the 11th day. Concentrations of tumor necrosis factor-α (TNF-α), interleukine-6 (IL-6) and serum C reactive protein (CRP) dropped earlier in the treatment group (on the 4th day) than that in the control group (on the 7th day). No difference was observed in pancreatic lesions between the control and treatment groups.Concentration of endotoxin and lactulose/manicol (L:M) ratio of urine did not change in treatment group, but those in the control group were elevated markedly. Compared with the treatment group, CD4:CD8 T cells ratio and immunoglobulin G (IgG) concentration in the control group decreased significantly.CONCLUSION: Compared to TPN, the combined therapy of EN and PN could improve the nutrition status and moderate the acute phase response obviously. Moreover, the integrity of enteric mucosa and immune function were protected more effectively in treatment group than in the control one. On the other hand, EN did not simulate the excretion of pancreas and avoid exaggerating the inflammation of pancreas. Thus,appropriate application of PN and EN appears to be more effective for patients with SAP.展开更多
AIM: We shall construct the small interfering RNA (siRNA) expression cassette (SEC) targeting activated K-ras gene sequence, identify more effective siRNA sequence against K-ras gene in human pancreatic cancer cell li...AIM: We shall construct the small interfering RNA (siRNA) expression cassette (SEC) targeting activated K-ras gene sequence, identify more effective siRNA sequence against K-ras gene in human pancreatic cancer cell line MiaPaCa-2 by SEC and reveal the anti-cancer effects of RNA interference (RNAi) and its therapeutic possibilities. METHODS: Three different sites of SECs were constructed by PCR. K1/siRNA,K2/siRNA and K3/siRNA are located at sites 194,491 and 327, respectively. They were transfected into MiaPaCa-2 cells by liposome to inhibit the expression of activated K-ras. In the interfering groups of sites 194 and 491, we detected the apoptosis in cells by FACS after they were incubated for 48 h, then we tested the alternation of K-ras gene in MiaPaCa-2 cells by RT-PCR immunofluorescence, respectively. RESULTS: Introduction of the Kl/siRNA and K2/siRNA against K-ras into MiaPaCa-2 cells leads to increased apoptosis, and the number of apoptotic cells is increased compared with control cells. The tests of RT-PCR immunofluorescence show the effects of inhibiting expression of activated K-ras gene by RNA interference in the Kl/siRNA and K2/siRNA groups. We also find that the introduction of K3/siRNA has no effect on MiaPaCa-2 cells. CONCLUSION: Kl/siRNA and K2/siRNA can inhibit the expression of activated K-ras but K3/siRNA has no effect, demonstrating that Kl/siRNA and K2/siRNA are effective sequences against K-ras gene and K3/siRNA are not. We conclude that specific siRNA against K-ras expression may be a powerful tool to be used therapeutically against human pancreatic cancer.展开更多
AIM: TO explore the ability of recombinant toxin luteinizinghormone releasing hormone-Pseudomonas aeruginosaexotoxin 40 (LHRH-PE40) and LHRH binding to LHRH receptor(LHRHR) on the membrane surface of human liver cance...AIM: TO explore the ability of recombinant toxin luteinizinghormone releasing hormone-Pseudomonas aeruginosaexotoxin 40 (LHRH-PE40) and LHRH binding to LHRH receptor(LHRHR) on the membrane surface of human liver cancerHEPG cells.METHODS: LHRH was labeled by using 12sI with enzymaticreaction. The affinity and receptor volume of LHP, H-PE40and LHRH binding to LHRHR on the membrane surface ofhuman liver cancer cells were measured with radioligandreceptor assay.RESULTS: The specific activity of LHRH labeled with 12sIwas 2.7x 104 kBq/l^L, and its radiochemical purity reachedto 99.2-99.7%. The binding of 12sI to LHRH was maximalfor 240 min in the warm cultivation, and this binding wasstabilized. The inhibiting rates of ~2SI-LHRH and LHRH onthe proliferation of human liver cancer HEPG cells werenot significantly different. On the basis of the saturationcurve of ~2SI-LHRH binding to the membrane LHRHR of HEPGcells, ~2SI-LHRH of lx10s cpm was selected for radioligandreceptor assay. The affinity constants (Kd) of LHRH-PE40and LHRH binding to the membrane LHRHR of HEPG cellswere 0.43~0.12 nmol/L and 4.86~ 1.47 nmol/L, respectively,and their receptor volumes were 0.37~0.15 l^mol/g and0.42=I=0.13 l^mol/g, respectively. The binding of LHRH-PE40to the membrane protein of normal liver cells was notobserved.CONCLUSION: The recombinant toxin LHRH-PE40 binding tothe membrane surface of LHRHR of human liver cancer HEPGcells was very strong, while the specific binding of it to normalliver cells was not observed. The results provide an importantexperimental basis for the clinical application of LHRH-PE.展开更多
AIM: To examine the effects of berberine, an isoquinoline alkaloid with a long history used as a tonic remedy for liver and heart, on ion channels of isolated rat hepatocytes.METHODS: Tight-seal whole-cell patch-clamp...AIM: To examine the effects of berberine, an isoquinoline alkaloid with a long history used as a tonic remedy for liver and heart, on ion channels of isolated rat hepatocytes.METHODS: Tight-seal whole-cell patch-clamp techniques were performed to investigate the effects of berberine on the delayed outward potassium currents (Ik), inward rectifier potassium currents (Ik1) and Ca^2+ release-activated Ca^+ currents (ICRAC) in enzymatically isolated rat hepatocytes.RESULTS: Berbenne 1-300 μmol/L reduced/K in a concentration-dependent manner with EC50 of 38.86=1=5.37 μmol/L and nH of 0.82±0.05 (n = 8). When the bath solution was changed to tetraethylammonium (TEA) 8 retool/L,IK was inhibited.Berberine 30 μmol/L reduced/K at all examined membranepote ntials, especially at potentials positive to +60 mV (n = 8,P<0.05 or P<0.01 vs control). Berberine had mild inhibitory effects on IK1 in rat hepatocytes. Berberine 1-300 μmol/L also inhibited ICRAC in a concentration-dependent fashion. The fitting parameters were EC50 = 47.20±10.86 μmol/L,nH= 0.71±0.09 (n = 8). The peak value of/CRAC in the I-Vrelationship was decreased by berberine 30 μmol/L at potentialnegative to -80 mV (n = 8, P<0.05 vscontrol). But the reverse potential of/CRAC occurred at voltage 0 mV in all cells.CONCLUSION: Berberine has inhibitory effects on potassium and calcium currents in isolated rat hepatocytes, which may be involved in hepatoprotection.展开更多
AIM: To study the effects of palmatine, a known inhibitoron delayed rectifier potassium current and L-type calciumcurrent (ICa,L) in guinea pig ventricular myocytes, on thepotassium and calcium currents in isolated ra...AIM: To study the effects of palmatine, a known inhibitoron delayed rectifier potassium current and L-type calciumcurrent (ICa,L) in guinea pig ventricular myocytes, on thepotassium and calcium currents in isolated rat hepatocytes.METHODS: Tight-seal wh ole-cell patch-clamp techniqueswere performed to investigate the effects of palmatine onthe delayed outward potassium currents (IK), inward rectifierpotassium current (IK1) and Ca2+ release-activated Ca2+current (ICRAC) in enzymatically isolated rat hepatocytes.RESULTS: Palmatine 0.3-100 μM reduced IK in a concentationdependent manner with EC50of 41.62±10.11 μM and nH,0.48±0.07 (n=8). The effect of the drug was poorly reversibleafter washout. When the bath solution was changed totetraethylammonium (TEA) 8 mM, IK was inhibited.Palmatine 10 μM and 100 μM shifted the I-V curves of IKdownward, and the block of IK was voltage-independent.Palmatine 0.3-100 μM also inhibited ICRAC in a concentration-dependent manner. The fitting parameters were as follows:ECs0=51.19±15.18 μM, and nH=0.46+0.07 (n=8). The peakvalue of ICRAC in the I-V relationship was decreased bypalmatine 10 μM and 100 μM. But the reverse potential ofIcRAcoCcurred at Voltage=0 mV in all cells. Palmatine 0.3-100 μM failed to have any significant effect on either inwardor outward components of IK1 at any membrane potentialexamined.CONCLUSION: The inhibitory effects on IK and ICRAC couldbe one of the mechanisms that palmatine exerts protectiveeffect on hepatocytes.展开更多
Objective To investigate the performance of soil-slurry bioreactor used for remediating contaminated soil with 4-nitrophenol (4-NP). Methods The slurry bioreactor was used to degrade different concentrations of 4-nitr...Objective To investigate the performance of soil-slurry bioreactor used for remediating contaminated soil with 4-nitrophenol (4-NP). Methods The slurry bioreactor was used to degrade different concentrations of 4-nitrophenol with or without inoculating the acclimated activated sludge. HPLC system (Hewlett-Packard model 5050 with a UV detector) was used for the quantification of 4-nitrophenol. Results The indigenous microorganisms exhibited a little activity for simulated soil with 50 mg 4-NP/kg soil. However, at the concentration of 10 mg 4-NPkg soil, a considerable degradation occurred within two weeks. It appeared that high concentrations of 4-nitrophenol apparently produced an inhibitory effect on microbial activity. For system receiving 50 mg 4-NP/kg soil, the maximum rate of 4-NP degradation measured in the reactor inoculated with 25 g sludge/kg soil was approximately 10 times higher than the uninoculated reactor, suggesting that the degradation rate of 4-nitrophenol could be enhanced greatly by means of inoculating acclimated sludge. Conclusion The addition of sludge capable of degrading 4-nitrophenol can result in enhance the degradation rate of 4-nitrophenol.展开更多
The abundances of long-lived radioactive elements Th and U observed in metal-poor halo stars can be used as chronometers to determine the age of individual stars, and hence set a lower limit on the age of the Galaxy a...The abundances of long-lived radioactive elements Th and U observed in metal-poor halo stars can be used as chronometers to determine the age of individual stars, and hence set a lower limit on the age of the Galaxy and hence of the universe. This radioactive dating requires the zero-decay productions of Th and U, which involves complicated r-process nucleosynthesis calculations. Several parametric r-process models have been used to calculate the initial abundance ratios of Th/Eu and U/Th, but, due to the sharp sensitivity of these models to nuclear physics inputs, the calculations have relatively large uncertainties which lead to large uncertainties in the age determinations. In order to reduce these uncertainties, we present a simple method to estimate the initial productions of Th and U, which only depends on the solar system abundances and the stellar abundances of stable r-process elements. From our calculations of the initial abundance ratios of Th/Eu and U/Th, we re-estimate the ages of those very metal-poor halo stars with published abundances of Th and U. Our age estimates are consistent, within the errors, with the other age determinations derived from r-process models, and offer useful constrains for r-process theoretical calculations. The advantages and limitations of our simple method of radioactive dating are discussed.展开更多
We present an atlas of a group of bright stars in the range of spectral classes F–G and luminosity classes I–V. The spectra were obtained with spectral resolution R ~ 15 000 within spectral region 4500–6620?. Typic...We present an atlas of a group of bright stars in the range of spectral classes F–G and luminosity classes I–V. The spectra were obtained with spectral resolution R ~ 15 000 within spectral region 4500–6620?. Typical spectra of stars with different metallicity [Fe/H] are included. We also show the digital version of the spectral data in FITS format.展开更多
High-resolution, high signal-to-noise ratio spectra have been obtained for 32 metal-poor stars. The equivalent widths of Li γ6708 ? were measured and the lithium abundances were derived. The average lithium abundance...High-resolution, high signal-to-noise ratio spectra have been obtained for 32 metal-poor stars. The equivalent widths of Li γ6708 ? were measured and the lithium abundances were derived. The average lithium abundance of 21 stars on the lithium plateau is 2.33±0.02 dex. The Lithium plateau exhibits a marginal trend along metallicity, dA(Li)/d[Fe/H] = 0.12±0.06, and no clear trend with the effective temperature. The trend indicates that the abundance of lithium plateau may not be primordial and that a part of the lithium was produced in Galactic Chemical Evolution (GCE).展开更多
The abundances of the wide binary pair HD 219175 A and B are determined andcompared using a line-by-line differential analysis. No evidence for difference has been found inthe abundances of Fe, O, Na, Mg, Al, Si, K, C...The abundances of the wide binary pair HD 219175 A and B are determined andcompared using a line-by-line differential analysis. No evidence for difference has been found inthe abundances of Fe, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Ni, Cu and Ba. Our resultssupport a physical relation between the two components of HD 219175.展开更多
We performed an extensive non-LTE analysis of the neutral sodium lines of Na I 5683/5688, 5890/5896, 6154/6161, and 8183/8195 in disk/halo stars of types F-K covering a wide metallicity range (-4 (?) [Fe/H] (?) +0.4),...We performed an extensive non-LTE analysis of the neutral sodium lines of Na I 5683/5688, 5890/5896, 6154/6161, and 8183/8195 in disk/halo stars of types F-K covering a wide metallicity range (-4 (?) [Fe/H] (?) +0.4), using our own data as well as data collected from the literature. For comparatively metal-rich disk stars (-1(?) [Fe/H] (?) +0.4) where the weaker 6154/6161 lines are the best abundance indicators, we confirmed [Na/Fe]- 0 with an 'upturn' (i.e., a shallow/broad dip around -0.5 (?) [Fe/H](?) 0) as already reported in previous studies. For the metal-deficient halo stars, where the much stronger 5890/5896 or 8183/8195 lines subject to considerable (negative) non-LTE corrections amounting to 0.5 dex have to be used, our analysis suggests mildly 'subsolar' [Na/Fe] values down to--0.4 (with a somewhat large scatter of-±0.2 dex) on the average at the typical halo metallicity of [Fe/H] --2, followed by a rise again to a near-solar ratio of [Na/Fe] - 0 at the very metal-poor regime [Fe/H]--3 to -4. These results are discussed in comparison with the previous observational studies along with the theoretical predictions from the available chemical evolution models.展开更多
The first mapping observations of the bipolar HII region S106 in HCN J = 3 - 2 line were made by KOSMA submillimeter telescope in April, 2004. The results show that there is a bipolar outflow centered on the high-mass...The first mapping observations of the bipolar HII region S106 in HCN J = 3 - 2 line were made by KOSMA submillimeter telescope in April, 2004. The results show that there is a bipolar outflow centered on the high-mass star S106 IRS4 and that the flat structure of molecular cloud core is perpendicular to the axis of the outflow. This image roughly corresponds to the optical image where a dark lane bisects the bipolar HII region. Together with the optical, infrared and radio data, we conclude that the central UC HII region and molecular outflow formed before the two lobes of the bipolar HII region, and that a neutral disk is responsible for the bipolar HII region and the outflow.展开更多
文摘AIM: To investigate the effect of nutritional support therapy on severe acute pancreatitis (SAP).METHODS: A total of 96 patients with severe acute pancreatitis were divided randomly into control and treatment groups.The former group received total parenteral nutrition (TPN)via central venous infusion, while parenteral nutrition (PN)and enteral nutrition (EN) therapies were applied in different phases for the latter group. The nutrition status, acute phase responses, pancreas lesions, enteric mucosa penetrability and immune functions were monitored.RESULTS: Body weight and prealbumin concentration were increased in treatment group, compared to those in the control group, but albumin concentration did not change significantly.Acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ)scores decreased after 7 d of treatment, whereas the scores of the control group decreased on the 11th day. Concentrations of tumor necrosis factor-α (TNF-α), interleukine-6 (IL-6) and serum C reactive protein (CRP) dropped earlier in the treatment group (on the 4th day) than that in the control group (on the 7th day). No difference was observed in pancreatic lesions between the control and treatment groups.Concentration of endotoxin and lactulose/manicol (L:M) ratio of urine did not change in treatment group, but those in the control group were elevated markedly. Compared with the treatment group, CD4:CD8 T cells ratio and immunoglobulin G (IgG) concentration in the control group decreased significantly.CONCLUSION: Compared to TPN, the combined therapy of EN and PN could improve the nutrition status and moderate the acute phase response obviously. Moreover, the integrity of enteric mucosa and immune function were protected more effectively in treatment group than in the control one. On the other hand, EN did not simulate the excretion of pancreas and avoid exaggerating the inflammation of pancreas. Thus,appropriate application of PN and EN appears to be more effective for patients with SAP.
文摘AIM: We shall construct the small interfering RNA (siRNA) expression cassette (SEC) targeting activated K-ras gene sequence, identify more effective siRNA sequence against K-ras gene in human pancreatic cancer cell line MiaPaCa-2 by SEC and reveal the anti-cancer effects of RNA interference (RNAi) and its therapeutic possibilities. METHODS: Three different sites of SECs were constructed by PCR. K1/siRNA,K2/siRNA and K3/siRNA are located at sites 194,491 and 327, respectively. They were transfected into MiaPaCa-2 cells by liposome to inhibit the expression of activated K-ras. In the interfering groups of sites 194 and 491, we detected the apoptosis in cells by FACS after they were incubated for 48 h, then we tested the alternation of K-ras gene in MiaPaCa-2 cells by RT-PCR immunofluorescence, respectively. RESULTS: Introduction of the Kl/siRNA and K2/siRNA against K-ras into MiaPaCa-2 cells leads to increased apoptosis, and the number of apoptotic cells is increased compared with control cells. The tests of RT-PCR immunofluorescence show the effects of inhibiting expression of activated K-ras gene by RNA interference in the Kl/siRNA and K2/siRNA groups. We also find that the introduction of K3/siRNA has no effect on MiaPaCa-2 cells. CONCLUSION: Kl/siRNA and K2/siRNA can inhibit the expression of activated K-ras but K3/siRNA has no effect, demonstrating that Kl/siRNA and K2/siRNA are effective sequences against K-ras gene and K3/siRNA are not. We conclude that specific siRNA against K-ras expression may be a powerful tool to be used therapeutically against human pancreatic cancer.
基金Supported by the Key Programs of National Science and Technology,No.96-901-05-101
文摘AIM: TO explore the ability of recombinant toxin luteinizinghormone releasing hormone-Pseudomonas aeruginosaexotoxin 40 (LHRH-PE40) and LHRH binding to LHRH receptor(LHRHR) on the membrane surface of human liver cancerHEPG cells.METHODS: LHRH was labeled by using 12sI with enzymaticreaction. The affinity and receptor volume of LHP, H-PE40and LHRH binding to LHRHR on the membrane surface ofhuman liver cancer cells were measured with radioligandreceptor assay.RESULTS: The specific activity of LHRH labeled with 12sIwas 2.7x 104 kBq/l^L, and its radiochemical purity reachedto 99.2-99.7%. The binding of 12sI to LHRH was maximalfor 240 min in the warm cultivation, and this binding wasstabilized. The inhibiting rates of ~2SI-LHRH and LHRH onthe proliferation of human liver cancer HEPG cells werenot significantly different. On the basis of the saturationcurve of ~2SI-LHRH binding to the membrane LHRHR of HEPGcells, ~2SI-LHRH of lx10s cpm was selected for radioligandreceptor assay. The affinity constants (Kd) of LHRH-PE40and LHRH binding to the membrane LHRHR of HEPG cellswere 0.43~0.12 nmol/L and 4.86~ 1.47 nmol/L, respectively,and their receptor volumes were 0.37~0.15 l^mol/g and0.42=I=0.13 l^mol/g, respectively. The binding of LHRH-PE40to the membrane protein of normal liver cells was notobserved.CONCLUSION: The recombinant toxin LHRH-PE40 binding tothe membrane surface of LHRHR of human liver cancer HEPGcells was very strong, while the specific binding of it to normalliver cells was not observed. The results provide an importantexperimental basis for the clinical application of LHRH-PE.
文摘AIM: To examine the effects of berberine, an isoquinoline alkaloid with a long history used as a tonic remedy for liver and heart, on ion channels of isolated rat hepatocytes.METHODS: Tight-seal whole-cell patch-clamp techniques were performed to investigate the effects of berberine on the delayed outward potassium currents (Ik), inward rectifier potassium currents (Ik1) and Ca^2+ release-activated Ca^+ currents (ICRAC) in enzymatically isolated rat hepatocytes.RESULTS: Berbenne 1-300 μmol/L reduced/K in a concentration-dependent manner with EC50 of 38.86=1=5.37 μmol/L and nH of 0.82±0.05 (n = 8). When the bath solution was changed to tetraethylammonium (TEA) 8 retool/L,IK was inhibited.Berberine 30 μmol/L reduced/K at all examined membranepote ntials, especially at potentials positive to +60 mV (n = 8,P<0.05 or P<0.01 vs control). Berberine had mild inhibitory effects on IK1 in rat hepatocytes. Berberine 1-300 μmol/L also inhibited ICRAC in a concentration-dependent fashion. The fitting parameters were EC50 = 47.20±10.86 μmol/L,nH= 0.71±0.09 (n = 8). The peak value of/CRAC in the I-Vrelationship was decreased by berberine 30 μmol/L at potentialnegative to -80 mV (n = 8, P<0.05 vscontrol). But the reverse potential of/CRAC occurred at voltage 0 mV in all cells.CONCLUSION: Berberine has inhibitory effects on potassium and calcium currents in isolated rat hepatocytes, which may be involved in hepatoprotection.
文摘AIM: To study the effects of palmatine, a known inhibitoron delayed rectifier potassium current and L-type calciumcurrent (ICa,L) in guinea pig ventricular myocytes, on thepotassium and calcium currents in isolated rat hepatocytes.METHODS: Tight-seal wh ole-cell patch-clamp techniqueswere performed to investigate the effects of palmatine onthe delayed outward potassium currents (IK), inward rectifierpotassium current (IK1) and Ca2+ release-activated Ca2+current (ICRAC) in enzymatically isolated rat hepatocytes.RESULTS: Palmatine 0.3-100 μM reduced IK in a concentationdependent manner with EC50of 41.62±10.11 μM and nH,0.48±0.07 (n=8). The effect of the drug was poorly reversibleafter washout. When the bath solution was changed totetraethylammonium (TEA) 8 mM, IK was inhibited.Palmatine 10 μM and 100 μM shifted the I-V curves of IKdownward, and the block of IK was voltage-independent.Palmatine 0.3-100 μM also inhibited ICRAC in a concentration-dependent manner. The fitting parameters were as follows:ECs0=51.19±15.18 μM, and nH=0.46+0.07 (n=8). The peakvalue of ICRAC in the I-V relationship was decreased bypalmatine 10 μM and 100 μM. But the reverse potential ofIcRAcoCcurred at Voltage=0 mV in all cells. Palmatine 0.3-100 μM failed to have any significant effect on either inwardor outward components of IK1 at any membrane potentialexamined.CONCLUSION: The inhibitory effects on IK and ICRAC couldbe one of the mechanisms that palmatine exerts protectiveeffect on hepatocytes.
文摘Objective To investigate the performance of soil-slurry bioreactor used for remediating contaminated soil with 4-nitrophenol (4-NP). Methods The slurry bioreactor was used to degrade different concentrations of 4-nitrophenol with or without inoculating the acclimated activated sludge. HPLC system (Hewlett-Packard model 5050 with a UV detector) was used for the quantification of 4-nitrophenol. Results The indigenous microorganisms exhibited a little activity for simulated soil with 50 mg 4-NP/kg soil. However, at the concentration of 10 mg 4-NPkg soil, a considerable degradation occurred within two weeks. It appeared that high concentrations of 4-nitrophenol apparently produced an inhibitory effect on microbial activity. For system receiving 50 mg 4-NP/kg soil, the maximum rate of 4-NP degradation measured in the reactor inoculated with 25 g sludge/kg soil was approximately 10 times higher than the uninoculated reactor, suggesting that the degradation rate of 4-nitrophenol could be enhanced greatly by means of inoculating acclimated sludge. Conclusion The addition of sludge capable of degrading 4-nitrophenol can result in enhance the degradation rate of 4-nitrophenol.
基金Supported by the National Natural Science Foundation of China.
文摘The abundances of long-lived radioactive elements Th and U observed in metal-poor halo stars can be used as chronometers to determine the age of individual stars, and hence set a lower limit on the age of the Galaxy and hence of the universe. This radioactive dating requires the zero-decay productions of Th and U, which involves complicated r-process nucleosynthesis calculations. Several parametric r-process models have been used to calculate the initial abundance ratios of Th/Eu and U/Th, but, due to the sharp sensitivity of these models to nuclear physics inputs, the calculations have relatively large uncertainties which lead to large uncertainties in the age determinations. In order to reduce these uncertainties, we present a simple method to estimate the initial productions of Th and U, which only depends on the solar system abundances and the stellar abundances of stable r-process elements. From our calculations of the initial abundance ratios of Th/Eu and U/Th, we re-estimate the ages of those very metal-poor halo stars with published abundances of Th and U. Our age estimates are consistent, within the errors, with the other age determinations derived from r-process models, and offer useful constrains for r-process theoretical calculations. The advantages and limitations of our simple method of radioactive dating are discussed.
基金Supported by the National Natural Science Foundation of China
文摘We present an atlas of a group of bright stars in the range of spectral classes F–G and luminosity classes I–V. The spectra were obtained with spectral resolution R ~ 15 000 within spectral region 4500–6620?. Typical spectra of stars with different metallicity [Fe/H] are included. We also show the digital version of the spectral data in FITS format.
基金Supported by the National Natural Science Foundation of China
文摘High-resolution, high signal-to-noise ratio spectra have been obtained for 32 metal-poor stars. The equivalent widths of Li γ6708 ? were measured and the lithium abundances were derived. The average lithium abundance of 21 stars on the lithium plateau is 2.33±0.02 dex. The Lithium plateau exhibits a marginal trend along metallicity, dA(Li)/d[Fe/H] = 0.12±0.06, and no clear trend with the effective temperature. The trend indicates that the abundance of lithium plateau may not be primordial and that a part of the lithium was produced in Galactic Chemical Evolution (GCE).
基金Supported by the National Natural Science Foundation of China.
文摘The abundances of the wide binary pair HD 219175 A and B are determined andcompared using a line-by-line differential analysis. No evidence for difference has been found inthe abundances of Fe, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Ni, Cu and Ba. Our resultssupport a physical relation between the two components of HD 219175.
文摘We performed an extensive non-LTE analysis of the neutral sodium lines of Na I 5683/5688, 5890/5896, 6154/6161, and 8183/8195 in disk/halo stars of types F-K covering a wide metallicity range (-4 (?) [Fe/H] (?) +0.4), using our own data as well as data collected from the literature. For comparatively metal-rich disk stars (-1(?) [Fe/H] (?) +0.4) where the weaker 6154/6161 lines are the best abundance indicators, we confirmed [Na/Fe]- 0 with an 'upturn' (i.e., a shallow/broad dip around -0.5 (?) [Fe/H](?) 0) as already reported in previous studies. For the metal-deficient halo stars, where the much stronger 5890/5896 or 8183/8195 lines subject to considerable (negative) non-LTE corrections amounting to 0.5 dex have to be used, our analysis suggests mildly 'subsolar' [Na/Fe] values down to--0.4 (with a somewhat large scatter of-±0.2 dex) on the average at the typical halo metallicity of [Fe/H] --2, followed by a rise again to a near-solar ratio of [Na/Fe] - 0 at the very metal-poor regime [Fe/H]--3 to -4. These results are discussed in comparison with the previous observational studies along with the theoretical predictions from the available chemical evolution models.
文摘The first mapping observations of the bipolar HII region S106 in HCN J = 3 - 2 line were made by KOSMA submillimeter telescope in April, 2004. The results show that there is a bipolar outflow centered on the high-mass star S106 IRS4 and that the flat structure of molecular cloud core is perpendicular to the axis of the outflow. This image roughly corresponds to the optical image where a dark lane bisects the bipolar HII region. Together with the optical, infrared and radio data, we conclude that the central UC HII region and molecular outflow formed before the two lobes of the bipolar HII region, and that a neutral disk is responsible for the bipolar HII region and the outflow.
