Biomedical subjects

Weidong Zhang

Publications and source records attributed to Weidong Zhang.

16 recordsLinked to original sources

PubMed2003

Comparison of several well-known controllers used in process control.

In this paper, several well-known design methods, PID control, Smith predictor, inferential control, internal model control, Dahlin controller, deadbeat control, and predictive control, are studied. A suboptimal Smith predictor is derived. The relationship among these methods is investigated. It is shown that these methods are equivalent to each other on certain premises. This explains why they are widely used in process control and provides insight into the work of bringing these techniques together to control system design. Examples are given to illustrate the result.

Journal Article↗

PubMed2003

The characterisation of polycyclic aromatic hydrocarbons emissions from burning of different firewood species in Australia.

Four kinds of woods used for residential heating in Australia were selected and burned under two burning conditions in a domestic wood heater installed in a laboratory. The selected wood species included pine (Pinus radiata), red gum (Eucalvptus camaldulensis), sugar gum (Eucalyptus cladocalyx) and yellow box (Eucalyptus melliodora). The two different burning conditions represented fast burning and slow burning, with the air inlet of the combustion chamber respectively 'full open' and 'half open'. By sampling and analysing particulate and gaseous emissions from the burning of each load of wood under defined experimental conditions, PAHs emissions and their profiles in the particulate and gaseous phases were obtained. 16 species out of the 18 selected PAHs were detected. Of these, seven species were detected in the gaseous phase and most were lower molecular weight compounds.Similarly, more than 10 species of PAHs were detected in the particulate phase and these were mostly heavier molecular weight compounds. Under both burning conditions, emission levels for total PAHs and total genotoxic PAHs were the highest for pine and lowest for sugar gum, with red gum being the second highest, followed by yellow box. Using the specific sampling method, gaseous PAHs accounted for above 90% mass fraction of total PAHs in comparison to particulate PAHs (10%). The majority of the genotoxic PAHs were present in the particulate phase. PAHs emission levels in slow burning conditions were generally higher than those in fast burning conditions.

Air Pollutants↗

PubMed2003

Tumour necrosis factor-alpha (TNF-alpha) transgene-expressing dendritic cells (DCs) undergo augmented cellular maturation and induce more robust T-cell activation and anti-tumour immunity than DCs generated in recombinant TNF-alpha.

Tumour antigen presentation by dendritic cells (DCs) to T cells in lymphoid organs is crucial for induction of anti-tumour immune responses. It has been previously reported that tumour necrosis factor-alpha (TNF-alpha) is required for DC activation and subsequent induction of optimal immune responses, and thus DCs for anti-tumour vaccination are often generated by culture in exogenous TNF-alpha. In the present study, we investigated the effect on anti-tumour immunity of vaccination with Mut1 tumour peptide-pulsed DCs engineered to express a TNF-alpha transgene. Our data shows that transfection of DCs with recombinant adenovirus AdV-TNF-alpha resulted in greater maturation of the DCs than occurred with control DCs cultured in exogenous TNF-alpha, as determined by up-regulated expression of pro-inflammatory cytokines (e.g. interleukins 1beta and 18), chemokines [e.g. interferon-gamma-inducible protein-10 and macrophage inflammatory protein-1beta (MIP-1beta)], the CC chemokine receptor CCR7, and immunologically important cell surface molecules (CD40, CD86 and intercellular adhesion molecule-1). These transgenic DCs stimulated stronger allogeneic T-cell responses in vitro and T-cell activation in vivo; displayed 2.4-fold enhanced chemotactic responses to the MIP-3betain vitro (P<0.05); and, perhaps most importantly, trafficked into the draining lymph nodes dramatically (seven-fold, P<0.01) more efficiently than the control DCs. Our data also demonstrate that vaccination of mice with Mut1 peptide-pulsed, AdV-TNF-alpha-transfected DCs stimulated more efficient in vitro Mut1-specific CD8+ cytotoxic T-cell responses and solid tumour immunity in vivo, when compared to the in vitro TNF-alpha-cultivated DCs. Thus, DCs engineered to secrete TNF-alpha may offer a new strategy in DC cancer vaccines.

Adenoviridae↗

PubMed2002

Enhancing antitumor by immunization with fusion of dendritic cells and engineered tumor cells.

A novel approach for a dentritic cells (DCs)-based tumor vaccine was developed for the formation of hybrid-engineered J558 after fusion with DCs. To make the hybrid-tumor vaccine generate more efficient specific CTL cytotoxicity against wild-type tumor cells, we genetically engineered tumor cells with mIL-12 gene prior to the cell fusion. mIL-12 was detected at 870 +/- 60 pg/(10(5) cells/ml) in the culture supernatants and the fusion ratio was about 30% by the co-focal microscopic analysis. Vaccination of mice with DCs fused with engineered J558 induced more efficient tumor-specific CTL cytotoxicity against wild-type tumor cells in vitro and with efficient antitumor immunity in vivo. These results suggest that this approach of using DCs fused with engineered tumor cells could be applied in clinical settings of DCs-based cancer vaccines.

Animals↗

PubMed2002

H(infinity) PID controller design for runaway processes with time delay.

This paper presents an efficient method for designing proportional-integra-derivative (PID) controllers for runaway processes with time delay. The method is developed based on the H(infinity) control theory in frequency domain. The constraints imposed by the internal stability and asymptotic properties of the closed-loop system are first investigated, a new procedure is then developed for analytically designing the controller, and simple design formulas are obtained. It is shown that the new controller can be designed to meet specified time domain performances. Typical design examples are provided to illustrate the proposed method.

Computer Simulation↗

PubMed2002

A new two-degree-of-freedom level control scheme.

In this paper, a two-degree-of-freedom level control scheme for delay free processes is analyzed. The nominal performance and robustness are examined. And sufficient and necessary conditions for robust stability are derived. An alternative level control scheme is developed for processes with dead time and suboptimal controllers that can produce smooth response are derived analytically based on the internal model control. The scheme has an important feature in that it is simple and transparent in design and in the corporation of performance and robust stability issues. Numerical examples are provided to compare the proposed scheme with those developed.

Equipment Design↗

PubMed2002

Design PID controllers for desired time-domain or frequency-domain response.

Practical requirements on the design of control systems, especially process control systems, are usually specified in terms of time-domain response, such as overshoot and rise time, or frequency-domain response, such as resonance peak and stability margin. Although numerous methods have been developed for the design of the proportional-integral-derivative (PID) controller, little work has been done in relation to the quantitative time-domain and frequency-domain responses. In this paper, we study the following problem: Given a nominal stable process with time delay, we design a suboptimal PID controller to achieve the required time-domain response or frequency-domain response for the nominal system or the uncertain system. An H(infinity) PID controller is developed based on optimal control theory and the parameters are derived analytically. Its properties are investigated and compared with that of two developed suboptimal controllers: an H2 PID controller and a Maclaurin PID controller. It is shown that all three controllers can provide the quantitative time-domain and frequency-domain responses.

Computer Simulation↗

PubMed2002

Optimal solution, quantitative performance estimation, and robust tuning of the simplifying controller.

Recently, a simplifying controller has been proposed based on the principal of simplification of the control system transfer functions, which offers improved control for processes with a large time delay. It is the purpose of this complementary paper to give a comprehensive analysis on the scheme. First, the relationship among the simplifying controller, the Smith predictor, and the internal model control are discussed. Second, an analytical design procedure is developed based on internal model control (IMC) and optimal solution is derived. Third, the problem of estimating the time domain performance of the closed loop system, quantitatively, is discussed. Fourth, a simple robust tuning procedure is presented. Numerical examples are provided to illustrate the proposed method.

Computer Simulation↗

PubMed2002

Comparison of bacterial regrowth in distribution systems using free chlorine and chloramine: a statistical study of causative factors.

Bacterial regrowth was investigated over a 15-month period in distribution systems (DSs) of Durham and Raleigh in North Carolina. These two water utilities were chosen because they are adjacent to one another, have similar service area characteristics, and treat surface waters of similar characteristics with conventional processes (coagulation-sedimentation and dual-media filtration). The finished waters have similar chemical quality and regrowth potential as measured by assimilable organic carbon (AOC). The major difference in treatment is the choice of final disinfectants (chlorine in Durham and chloramine in Raleigh). Ten sampling sites (monthly sampling) were chosen in each system to give wide geographic coverage and correspondingly, a wide range of water residence times. Significant losses were observed in both chlorine and chloramine residual in the DSs that produced bacterial regrowth as measured by heterotrophic plate count (HPC). The frequency distributions for log HPC (133 observations from Durham and 135 observations from Raleigh) were statistically the same in the chlorinated and chloraminated DSs. A correlation analysis indicated that disinfectant residual is the most important factor determining HPC level. However, the resulting R2 value for a non-linear regression model that also included AOC, temperature, and pH as independent variables was less than 0.7. Bacterial regrowth as measured by HPC, is dependent upon a complex interaction of chemical, physical, and operational parameters that may not be captured by such a simple statistical relationship.

Bacteria↗

PubMed2002

Engineered fusion hybrid vaccine of IL-4 gene-modified myeloma and relative mature dendritic cells enhances antitumor immunity.

Dendritic cell (DC)-tumor fusion hybrid vaccine which facilitates antigen presentation represents a new powerful strategy in cancer therapy. In the present study, we investigated the antitumor immunity derived from vaccination of fusion hybrids between wild-type J558 or engineered J558-IL-4 myeloma cells secreting cytokine interleukin-4 (IL-4) and immature DCs (DC(IMAT)) or relative mature DCs (DC(RMAT)). DC(RMAT) displayed an up-regulated expression of immune molecules (Ia(d), CD40, CD54, CD80 and CD86) and certain cytokines/chemokines, and enhanced ability of allogeneic T cell stimulation when compared to DC(IMAT). These DCs were fused with myeloma cells by polyethylene glycol (PEG). The fusion efficiency was approximately 20%. Our data showed that immunization of C57BL/6 mice with DC(RMAT)/J558 hybrids induced protective immunity against a high dose of J558 tumor challenge (1x10(6) cells) in 3 out of 10 immunized mice, compared with no protection seen in mice immunized with DC(IMAT)/J558 hybrids. Furthermore, immunization of mice with engineered DC(RMAT)/J558-IL-4 hybrids elicited stronger J558 tumor-specific cytotoxic T lymphocyte (CTL) responses in vitro and induced more efficient protective immunity (10/10 mice; tumor free) against J558 tumor challenge in vivo than DC(RMAT)/J558 hybrid vaccines. The results demonstrate the importance of DC maturation in DC-tumor hybrid vaccines and indicate that the engineered fusion hybrid vaccines which combine gene-modified tumor and DC vaccines may be an attractive strategy for cancer immunotherapy.

Animals↗

PubMed2002

Adenovirus-mediated CD40 ligand gene-engineered dendritic cells elicit enhanced CD8(+) cytotoxic T-cell activation and antitumor immunity.

CD40L, the ligand for CD40 on dendritic cells (DCs), plays an important role in their activation and is essential for induction of antigen-specific T-cell responses. In the present study, we investigated the efficacy of antitumor immunity induced by vaccination with DCs engineered to express CD40L and pulsed with Mut1 tumor peptide. Our data show that transfection of DCs with recombinant adenovirus AdV-CD40L resulted in activation of DCs with up-regulated expression of proinflammatory cytokines (IL-1beta and IL-12), chemokines (RANTES, IP-10, and MIP-1alpha), and immunologically important cell surface molecules (CD54, CD80, and CD86). Our data also demonstrate that DCs transfected with AdV-CD40L (DC(CD40L)) are able to stimulate enhanced allogeneic T-cell proliferation and Mut1-specific CD8(+) cytotoxic T-cell responses in vitro. Vaccination of mice with Mut1 peptide-pulsed control virus-transfected DC (DC(pLpA)) could only protect mice from challenge of a low dose (0.5 x 10(5) cells per mouse, 8/8 mice), but not a high dose (3 x 10(5) cells per mouse, 0/8 mice) of 3LL tumor cells. However, vaccination of Mut1 peptide-pulsed AdV-CD40L-transfected DC(CD40L) induced an augmented antitumor immunity in vivo by complete protection of mice (8/8) from challenge of both low and high doses of 3LL tumor cells. Thus, DCs engineered to express CD40L by adenovirus-mediated CD40 ligand gene transfer may offer a new strategy in production of DC cancer vaccines.

Adenoviridae↗

PubMed2002

[Induction of Th1 immune response against tumor by genetically engineered fusion of tumor cells and dendritic cells].

OBJECTIVE: To study the antitumor activity of engineered fusion of tumor cell and dendritic cells (DC). METHODS: J558 tumor cells were transfected with mouse IL-12 (mIL-12) gene and then fused with DCs to develop a hybrid-engineered tumor vaccine. BALB/c mice were challenged with wild-type J558 tumor cells 14 days after vaccinated with hybrid-engineered J558. RESULTS: mIL-12 was detected at (870 +/- 60) pg.(10(5) cells)(-1).ml(-1) in the culture supernatants and the cell-fusion rate was about 30% by co-focal microscopy. In addition, the lymphocytes from popliteal nodes and groin nodes of these mice vaccinated with hybrid-engineered J558 secreted higher levels of IFN-gamma than that of other control mice, and vaccination of mice with the fusion vaccine induced more efficient tumor-specific CTL cytotoxicity against wild-type tumor cells in vitro and with efficient antitumor immunity in vivo. CONCLUSION: It suggested that vaccination of mice with the fusion vaccine induced stronger Th1-dominant responses and this approach could perhaps be applied to clinical settings of DCs-based cancer vaccines.

Animals↗

PubMed2002

[Nonsteroidal anti-inflammatory drugs and the risk of polyposis, colon carcinoma and rectal carcinoma].

OBJECTIVE: To probe the risk of colorectal polyp, colon and rectal carcinoma and the intake of NSAIDs. METHODS: Case-control study participants were from patients who underwent colonoscopy at different hospitals, the persons with the above disease was as cases, and those without the above diseases was as controls. Use of NSAIDs was assessed by interviewing the participants with a questionnaire which include a list of NSAIDs and related dietary and life style factors and family history. RESULTS: There are 37 cases of colorectal polyp, 105 cases of colon carcinoma and 142 cases of rectal carcinoma and 66 controls. Adjusted for potential confounders, the risk of colorectal polyposis, colon carcinoma and rectal carcinoma were markedly reduced by NSAIDs. The OR values were 0.21 (95% CI 0.07-0.65, P = 0.007), 0.13 (95% CI 0.05-0.35, P < 0.001), 0.15 (95% CI 0.11-0.58, P < 0.001) respectively. The risk of the above diseases were also reduced markedly by aspirin, the OR values were 0.265 (95% CI 0.07-0.96, P = 0.044), 0.10 (95% CI 0.03-0.35, P < 0.001), 0.15 (95% CI 0.04-0.49, P = 0.002) respectively. The risk of colon carcinoma was also reduced by profen, with the OR being 0.11 (95% CI 0.02-0.64, P = 0.014). CONCLUSIONS: Aspirin and other NSAIDs could reduced the risk of colorectal polyp, colon carcinoma and rectal carcinoma markedly. Aspirin was the most prospective chemopreventive agents for colorectal polyp, colon and rectal carcinoma for its capability of reducing the risk of cardio-cerebral vascular disease as well.

Adult↗

PubMed2002

The relativity between Streptococcus sanguis group and coronary heart disease.

OBJECTIVE: To study the relativity between Streptococcus sanguis group (SSG) and coronary heart disease (CHD). METHODS: 41 individuals were diagnosed with CHD and 18 normals served as controls. All of them had undergone coronary angiography. Their social class (including education and wages), smoking, drinking, blood lipids and oral health were also recorded. SSG in saliva and subgingival plaque were cultivated in NAYS-B agar plates and counted. SSG were identified into species with routine biochemical reaction and AP-PCR. RESULTS: In the multiple step regression analysis, the amount of SSG in saliva and subgingival plaque were positively associated with severe coronary atheromatosis after adjusting the classical risk factors of CHD. The average amount of SSG in saliva was (435 +/- 422) x 10(8) CFU/L in CHD group and (358 +/- 540) x 10(8) CFU/L in control group, F = 2.72, P = 0.08; the average amount of SSG in incisor was (331 +/- 484) x 10(7) CFU/L in CHD group and (98 +/- 164) x 10(7) CFU/L in control group, F = 5.54, P = 0.02; the average amount of SSG in molar was (352 +/- 381) x 10(7) CFU/L in CHD group and (185 +/- 232) x 10(7) CFU/L in control group, F = 2.86, P = 0.10. S. sanguis and S. gordonii were more in CHD group than in control group (P < 0.05), whereas S. mitis and S. oralis were the same in two groups (P > 0.05). CONCLUSION: The increase of SSG in oral floras may play an important role in the occurrence of CHD.

Aged↗

PubMed2002

[Studies on immunocompetent constituents of Patrinia scabra Bunge].

Five compounds were isolated from the roots of Patrinia scabra Bunge separated and purified on sillica gel column chromatography. Their structures were elucidated on the physico-chemical properties and spectral data as lariciresinol(I), syringaresinol(II), scopoletin(III), quercetin(IV), ferulaic acid(V). All compounds were obtained from P. scabra for the first time. In vitro biological test of these compounds showed that syringaresinol was able to stimulate T and B lymphocyte proliferation.

B-Lymphocytes↗

PubMed2002

TNF-alpha gene-modified dendritic cells act as more potent adjuvants for peptide delivery to induce specific antitumor immunity in mice.

OBJECTIVE: To investigate the antitumor immune efficiency of mouse dendritic cells (mDCs) by using adenovirus-mediated tumor necrosis factor-alpha (AdV-TNF-alpha) gene transfer. METHODS: MDCs infected with AdV-TNF-alpha and AdV-pLpA (no gene insert) at 100 multiplicity of infection (MOI) were analyzed by RNase protection assay for their cytokine secretion. Mixed lymphocyte reactions were also performed to analyze their capacity for alloantigen-presentation. C57BL/6 mice were challenged with R3LL tumor cells (Lewis lung carcinoma line) 10 days after vaccination with different engineered DCs and regular DCs as well. RESULTS: Compared to AdV-pLpA and mock-infected DCs, AdV-TNF-alpha-infected DCs displayed up-regulated expression of alpha tumor necrosis factor, interleukin-12 (IL-12), interleukin-18 (IL-18) and granulocyte macrophage colony stimulation factor (GM-CSF), and indicated stronger allogeneic T cell proliferative responses. Furthermore, vaccination of mice with dendritic cell tumor necrosis factor-alpha (DCTNF-alpha) pulsed with Mut1 peptide induced more efficient tumor-specific cytotoxic T lymphocyte (CTL) cytotoxicity against R3LL tumor cells in vitro and with efficient antitumor immunity in vivo. CONCLUSION: This type of engineered DCs could be applied in clinical settings of DC-based cancer vaccines.

Adenoviridae↗