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Zhang Lin

Publications and source records attributed to Zhang Lin.

14 recordsLinked to original sources
PubMed2006

A multistep oriented attachment kinetics: coarsening of ZnS nanoparticle in concentrated NaOH.

Crystal growth of ZnS nanoparticles during hydrothermal coarsened in 4 M NaOH occurs via a two-stage process. In the first stage, the primary particles grow into a size over hundred times of the original volume. The initial growth rate can be fitted by an asymptotic curve. High-resolution transmission electron microscope (HRTEM) data indicate that in this stage, crystal growth mainly occurs via a multistep crystallographically specific oriented attachment (OA). The higher the coarsening temperature, the earlier the first stage ends. In the second stage, an abrupt transition from asymptotic to square parabola growth kinetics occurs. The crystal growth data can be fitted by a standard Ostwald ripening (OR) model consistent with growth controlled by dissolution/precipitation of ions in solution. HRTEM data indicate that a minor amount of OA-based growth also occurs in the early period of the second stage. A new multistep OA kinetics model analogous to the reaction between molecules was proposed to illustrate the asymptotic growth in the first stage of coarsening. The effect of concentrated NaOH was discussed and proved to be the key that hindered the OR process, attributing to the almost exclusive pure OA-based growth of ZnS particles in the first stage.

Journal Article↗
PubMed2006

A thermodynamically stable nanophase material.

Nanoparticles are metastable relative to the equivalent bulk material due to the positive excess interfacial free energy (IFE). Previous studies have shown that, with increasing surface interaction strength, the IFE diminishes but remains positive. We describe an experimental multicomponent system in which a nanoscale ZnS material is thermodynamically favored and can be formed at the expense of bulk ZnS. In 17 M sodium hydroxide solution, at 230 degrees C, both 3 nm ZnS nanoparticles and bulk ZnS are transformed into sheetlike nanocrystals with a ZnS polytype structure. Our results are theoretically compatible with the concept of a negative IFE, although not with the assumption of constant interface composition. We clarify the meaning of an effective negative IFE and present the necessary conditions for strong chemical surface interactions to stabilize nanoscale inorganic materials relative to bulk matter. Our results show that synthesis methods employing thermodynamic controls can produce nanomaterials with novel morphology.

Journal Article↗
PubMed2006

The phosphoinositide 3-kinase/Akt-signal pathway mediates proliferation and secretory function of hepatic sinusoidal endothelial cells in rats after partial hepatectomy.

OBJECTIVE: To investigate the role of AKT signaling pathway in hepatic sinusoidal endothelial cells (SECs) early after partial hepatectomy in rats and the regulatory mechanisms involved. METHODS: The animal model of 70% hepatectomy was made. Hepatic SECs were isolated and cultured according to Braet et al.'s method with some modifications. The cultured hepatic SECs were divided into two groups: 70% partial hepatectomy groups and LY294002 group (LY). We observed the expressions of AKT and NF-kappaB in cultured hepatic SECs by Western blot, measured the levels of NO, NOs, IL-6, and HGF in the supernatants of hepatic SEC cultures and [3H]thymidine incorporation, and analyzed cell cycle of cultured hepatic SECs by flow cytometer. The relationship of the Akt pathway with secretions and proliferation of hepatic SECs after partial hepatectomy was probed. RESULTS: The levels of Akt protein expression increased significantly after partial hepatectomy in OG group and with a peak at 24 h post operation. Meanwhile, there was a markedly increase in phosphorylated Akt protein during 2-72 h after operation. But the expression and activity of Akt protein did not change significantly after partial hepatectomy in the LY group. So, partial hepatectomy can marked induce Akt expression and result in rapid and marked phosphorylation of Akt from 2 to 72 h thereafter. The changes of NF-kappaB expression in cultured hepatic SECs were similar to those of Akt expression after operation. The concentrations of HGF and IL-6 in the supernatants of cultured hepatic SECs were relatively low in the LY group, and were markedly increased after partial hepatectomy, with a peak at 24 h in the OG group. There were significant differences between the OG and LY groups at 6 and 24 h (P < 0.05). Both NO and NOS secretion was increased in the OG group compared to the LY group within 24 h after partial hepatectomy. But the secretion of NO and NOS was increased more markedly in the LY group than that in the OG beyond 24 h. These findings suggest that the secretion of the cytokines by hepatic SECs is mediated by Akt signaling. Akt signaling pathway in relationship with proliferation of hepatic SECs and suppression of apoptosis. In OG group, the hepatic SECs in S and G2/M obviously increased. The proliferative index of hepatic SECs in OG group had significant differences with that in LY group at 6, 24, and 72 h, P < 0.05. Meanwhile, the cells of apoptosis in OG group were very low, and the cells in LY group gradually increased. CONCLUSIONS: These results suggest that AKT signaling pathway plays a crucial role in mediating proliferating and secreted signals in hepatic SECs. AKT has been suggested to play a pivotal role in early liver regeneration involved in the induction of secreted cytokines and proliferation of hepatic SECs.

Animals↗
PubMed2006

Hepatic sinusoidal endothelial cells promote hepatocyte proliferation early after partial hepatectomy in rats.

BACKGROUND: We undertook this study in rats to investigate the role of hepatic sinusoidal endothelial cells (SECs) in hepatocyte proliferation early after partial hepatectomy and the regulatory mechanisms involved. METHODS: The animal model of 70% hepatectomy was made. Hepatic SECs and hepatocytes were isolated and cultured according to the method of Braet et al. with some modifications. Levels of nitric oxide (NO), interleukin-6 (IL-6), and hepatic growth factor (HGF) in the supernatants of hepatic SEC cultures were measured, and the expression of HGF mRNA by hepatic SECs was analyzed. The relationship between the supernatants of hepatic SEC cultures and hepatocyte proliferation was probed. (3)H-thymidine incorporation and the proliferating cell nuclear antigen (PCNA) labeling index of hepatocytes were used as signs of hepatocyte proliferation. RESULTS: Levels of NO, IL-6, and HGF in the supernatants of hepatic SECs cultures were increased markedly 6 and 24 h after hepatectomy and then were decreased gradually. The expression of HGF mRNA by cultured SECs was increased markedly 6 and 24 h after hepatectomy, with a peak 6 h after hepatectomy. The PCNA labeling index and (3)H-thymidine incorporation of hepatocytes started to increase 6 h after hepatectomy, with a peak at 24 h. Hepatic SECs were isolated from rats 24 h after partial hepatectomy and cultured for 24 h, and the culture supernatants were obtained. The supernatants not only significantly enhanced the PCNA labeling index and (3)H-thymidine incorporation of proliferating hepatocytes isolated from rats after partial hepatectomy but also obviously increased the DNA synthesis of quiescent hepatocytes from the control rats. The extent of hepatocyte proliferation was closely related to the amount of the SEC culture supernatants added in both rats after partial hepatectomy and control rats. CONCLUSIONS: These results suggest that cytokines (such as IL-6, HGF and NO) secreted by SECs play important roles in liver regeneration early after partial hepatectomy. We speculate that activated hepatic SECs secrete some substances that induce or trigger liver regeneration after partial hepatectomy.

Animals↗
PubMed2006

Surface chemistry controls crystallinity of ZnS nanoparticles.

Combined small-angle and high energy wide-angle X-ray scattering measurements of nanoparticle size and structure permit interior strain and disorder to be observed directly in the real-space pair distribution function (PDF). PDF analysis showed that samples of ZnS nanoparticles with similar mean diameters (3.2-3.6 nm) but synthesized and treated with different low-temperature procedures possess a dramatic range of interior disorder. We used Fourier transform infrared spectroscopy to detect the surface species and the nature of surface chemical interactions. Our results suggest that there is a direct correlation between the strength of surface-ligand interactions and interior crystallinity.

Crystallization↗
PubMed2006

A computer evaluation of ventilation performance in a negative-pressure operating theater.

BACKGROUND: A negative-pressure operating theater is required to limit the spread of respiratory diseases in patients with severe acute respiratory syndrome, tuberculosis, avian influenza, or similar infectious diseases. In Hong Kong, we converted a conventional operating theater into a negative-pressure operating theater that has been in service for more than a year. In this article, we introduce its ventilation design and evaluate the airflow performance in relation to different combinations of medical lamp configurations and modes of launching infectious particles into the room air. METHODS: We used a computational fluid dynamics technique for the numerical analysis. RESULTS: Our analyses showed that the airflow performance in the negative-pressure operating theater was satisfactory and comparable to the original positive-pressure design. The airflow pattern effectively controlled the dispersion of infectious particles. Our calculations demonstrated that the airflow contained the dispersion of infectious particles released from the patient sufficiently to protect the surgical team, and vice versa. CONCLUSIONS: Computational fluid dynamics can be used to assess airflow in a negative-pressure operating room and model the dispersion of infectious particles from the patient.

Computer Simulation↗
PubMed2005

Bacillus sp. B16 kills nematodes with a serine protease identified as a pathogenic factor.

An endospore-forming bacterium, strain B16, was isolated from a soil sample and identified as a Bacillus sp. The strain presented remarkable nematotoxic activity against nematode Panagrellus redivivus. The crude extracellular protein extract from culture supernatant of the bacteria killed about 80% of the tested nematodes within 24 h, suggesting the involvement of extracellular proteases. A homogeneous extracellular protease was purified by chromatography, and the hypothesis of proteinaceous pathogeny in the infection of B16 strain was confirmed by the experiments of killing living nematodes and by the degradation of purified nematode cuticle when treated with the homogenous protease. The gene for the virulence protease was cloned, and the nucleotide sequence was determined. The deduced amino acid sequence showed significant similarity with subtilisin BPN' but low homology with the other cuticle-degrading proteases previously reported in fungi. Characterization of the purified protease revealed the molecular mass of 28 kDa and the optimum activity at pH 10, 50 degrees C. The purified protease can hydrolyze several native proteinaceous substrates, including collagen and nematode cuticle. To our knowledge, this is the first report of a serine protease from a Bacillus genus of bacteria that serves as a pathogenic factor against nematodes, an important step in understanding the relationship between bacterial pathogen and host and in improving the nematocidal activity in biological control.

Amino Acid Sequence↗
PubMed2003

Assessment of disability, social and economic situations of people affected by leprosy in Shandong Province, People's Republic of China.

With the decline in prevalence of leprosy, social and economic rehabilitation (SER) has become a major priority in leprosy control programme in Shandong Province. In the preparative phase of an SER programme, a province-wide survey was conducted with a semi-structured questionnaire in order to provide policy makers and programme managers with some basic information on the disability, and social and economic situation of the people affected by leprosy. This paper presents the results of a study in the people affected by leprosy living in the communities.

Activities of Daily Living↗
PubMed2003

Role of leprosy villages and leprosaria in Shandong Province, People's Republic of China: past, present and future.

In the late phase of the leprosy control programme in Shandong Province, People's Republic of China, there are a few old and disabled ex-patients living in 54 leprosy villages/leprosaria. The small, and declining number of patients makes the running of these leprosy villages/leprosaria uneconomic. In this paper, we review the history and the role of leprosy villages/leprosaria in the care of leprosy patients and the control programme in Shandong province. We then analyse the present situation of the 643 people still living in these leprosy villages/leprosaria, using information collected from a questionnaire-based survey. Finally, we offer some suggestions and recommendations for policy makers and leprosy control managers, in order to improve the present situation and make better use of existing resources.

Activities of Daily Living↗