| 1. |
- Dunham, I, et al.
(författare)
-
The DNA sequence of human chromosome 22
- 1999
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 402:6761, s. 489-495
-
Tidskriftsartikel (refereegranskat)
|
|
| 2. |
- Wang, Feiyue, et al.
(författare)
-
Surface properties of natural aquatic sediments
- 1997
-
Ingår i: Water Research. - 0043-1354 .- 1879-2448. ; 31:7, s. 1796-1800
-
Tidskriftsartikel (refereegranskat)abstract
- Eleven geographically and hydrologically diverse sediment samples were collected from major rivers of China and determined for the surface properties. The results indicate the sediments have a large variation in surface area (6.9-16.0 m(2)/g of SSA(N2), 35.6-73.2 m(2)/g Of SSA(CPB), surface site density (10.3-149.8 mu mol/g) and surface acidity constants (1.56-2.50 of pK(s.a1)(int), and 3.75-5.58 of pK(s.a2)(int)) but a small difference in PZSE (3.0-4.0). Within the pH range 3.0-9.0, all sediments present negative surface charges. Their surface charge distribution curves with pH extend between these of SiO2, montmorillonite. kaolinite, alpha-MnO2, calcite and gamma-Al2O3;. Correlation analysis reveals that surface area and surface site density of the sediments are correlated strongly with reactive and amorphous iron oxides, total aluminum, clay and total organic carbon, while surface acidity constants, PZSE and the permanent structural charge only show a weak correlation with total aluminum in the sediments.
|
|
| 3. |
|
|
| 4. |
- Chen, Ke Wang, et al.
(författare)
-
Estimation of the Primary Current in a Saturated Transformer
- 1991
-
Ingår i: Proceedings of the 30th IEEE Conference on Decision and Control. - Linköping : Linköping University. - 0780304500 ; , s. 2363-2365 vol.3
-
Konferensbidrag (refereegranskat)abstract
- It is pointed out that, when a current in a power system is measured using a transformer, the measurement can be distorted by transformer saturation. The authors examine two methods of estimating the primary current from the secondary in the presence of saturation. The first is based on an extended Kalman filter, while the second is based on an off-line Gauss-Newton method
|
|
| 5. |
|
|
| 6. |
- Chen, Zheng-wang
(författare)
-
Isolation and characterization of novel intestinal polypeptides of the enteroinsular and brain-gut axes and of macrophages
- 1997
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The gastrointestinal tract has been recognized as our largest endocrine organ, from which many peptide hormones, neuropeptides and growth factors have been isolated. There is also increasing evidence that the gastrointestinal tract can be considered as our largest immune organ, from which many antibacterial peptides, cytokines, cytotoxins and chemokines have been characterized. Different entero-endocrine cells, peptidergic nerve terminals and immune cells are found in this organ. This thesis describes the isolation and characterization, from intestinal tissues, of seven polypeptides, five porcine [daintain/AIF1, diazepam binding inhibitor (DBI), dopuin, pancreatic polypeptide (PP), vimentin-37] and two from chicken (DBI1-86 and DBI35-86). These peptides were first detected in chromatographic peptide fractions that influenced the glucose-induced secretion of insulin from rat, isolated pancreatic glands or islets. Purification was guided by monitoring this effect or chemically by analysis for the presence of cyst(e)ine peptides. The polypeptides dopuin (do, many; pu, proline) and daintain- /AIF1 (da, big; in, influencing; tai, peptide; in, insulin secretion /allograft inflammatory factor 1) represent novel structures. The multifunctional peptide DBI and the peptide hormone PP have now been isolated from intestinal tissues, while chicken DBI and its novel, processed form DBI35-86 represent peptides now isolated from avian sources. Both of the purified chicken DBI forms inhibit glucose-induced insulin release in vitro, and were not known in structure earlier. Dopuin is a 62-residue polypeptide with a high content of pro-line in its N-terminal part and a high proportion of histidine in its C-terminal part. Both proline and histidine are important residues for specific structures and specialized functions. Six half-cystine residues are present and shown to be involved in three intrachain di-sulphide bridges (Cys22-25, 23-54, 35-44) which contribute to a tightly folded core segment in the molecular structure. At 10 nM concentration, the peptide has an inhibitory tendency on glucose induced insulin release in vitro. Daintain/AIFI consists of 146 amino acid residues and is N-terminally acetyl blocked. An internal 44-residue segment with a sequence pattern (---KR--- KK---GKR---) resembles that found in the structural theme of peptide hormone precursors and of the GKR segment for C-terminal amide formation during the processing of peptide hormones. Daintain/AIFIis immunohistochemically localized to microglial cells in the central nervous system, to macrophages, and to tissue-specialized macrophages such as dendritic or Kupffer's cells in the immune system of different tissues. Its weakly insulin-suppressing activity in vitro, dual influence on glucose-stimulated insulin secretion in vivo and relative abundance in macrophages of the pancreatic islets of prediabetic and newly diabetic BB rats raise the possibility that daintain/AIFI has a role in the pathogenesis of insulin dependent diabetes mellitus and other autoimmune diseases.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Parkkinen, Jyrki, et al.
(författare)
-
Distribution of hyaluronan in articular cartilage as probed by a biotinylated binding region of aggrecan.
- 1996
-
Ingår i: Histochemistry and Cell Biology. - : Springer. - 0948-6143 .- 1432-119X. ; 105:3, s. 187-194
-
Tidskriftsartikel (refereegranskat)abstract
- The proportion of total tissue hyaluronan involved in interactions with aggrecan and link protein was estimated from extracts of canine knee articular cartilages using a biotinylated hyaluronan binding region-link protein complex (bHABC) of proteoglycan aggregate as a probe in an ELISA-like assay. Microscopic sections were stained with bHABC to reveal free hyaluronan in various sites and zones of the cartilages. Articular cartilage, cut into 20 microns-thick sections, was extracted with 4 M guanidinium chloride (GuCl). Aliquots of the extract (after removing GuCl) were assayed for hyaluronan, before and after papain digestion. The GuCl extraction residues were analyzed after solubilization by papain. It was found that 47-51% of total hyaluronan remained in the GuCl extraction residue, in contrast to the 8-15% of total proteoglycans. Analysis of the extract revealed that 24-50% of its hyaluronan was directly detectable with the probe, while 50-76% became available only after protease digestion. The extracellular matrix in cartilage sections was stained with the bHABC probe only in the superficial zone and the periphery of the articular surfaces, both sites known to have a relatively low proteoglycan concentration. Trypsin pretreatment of the sections enhanced the staining of the intermediate and deep zones, presumably by removing the steric obstruction caused by the chondroitin sulfate binding region of aggrecans. Enhanced matrix staining in these zones was also obtained by a limited digestion with chondroitinase ABC. The results indicate that a part of cartilage hyaluronan is free from endogenous binding proteins, such as aggrecan and link protein, but that the chondroitin sulfate-rich region of aggrecan inhibits its probing in intact tissue sections. Therefore, hyaluronan staining was more intense in cartilage areas with lower aggrecan content. A large proportion of hyaluronan resists GuCl extraction, even from 20-micrograms-thick tissue sections.
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Wang, Chen, et al.
(författare)
-
Dysprosium-enhanced MR imaging for tumor tissue characterization : an experimental study in a human xenograft model
- 1997
-
Ingår i: Acta Radiologica. - 0284-1851 .- 1600-0455. ; 38:2, s. 281-286
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To evaluate dysprosium-enhanced MR imaging for differentiation between morphologically intact and necrotic tumor tissue in a tumor model. MATERIAL AND METHODS: A human colon carcinoma was transplanted subcutaneously into 9 nude (immunodeprived) rats. MR imaging was performed before and after injection of the dysprosium agent Dy-DTPA-BMA. T1-, T2- and T2*-weighted sequences were acquired. The tumors were dissected, histological sections were prepared, and compared with corresponding MR images. RESULTS: In intact tissue, the MR signal intensity in the T2- and T2*-weighted images decreased after Dy injection and the delineation of the intact regions were sharp and corresponded well to the gross histological sections. CONCLUSION: Dy-enhanced MR imaging facilitated the differentiation between intact and necrotic tumor tissue.
|
|
| 13. |
|
|
| 14. |
- Wang, Chen
(författare)
-
Mangafodipir trisodium (MnDPDP)-enhanced magnetic resonance imaging of the liver and pancreas
- 1998
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Contrast-enhanced magnetic resonance imaging (MRI) of the liver and pancreas is frequently performed to improve the sensitivity and specificity of lesion detection in these organs. The concept of using tissue-specific contrast media is to selectively enhance the normal parenchyma, but not lesions, so that the contrast between tumorous and normal tissue is increased, and lesion detectability improved. Mangafodipir trisodium (MnDPDP) has been developed as a hepatocellular-specific contrast agent, but uptake has also been found in pancreatic tissue. In this study the safety and diagnostic efficacy of MnDPDP were investigated in both healthy volunteers and patients with liver and pancreatic tumors.In healthy volunteers (n=8), dose-dependent enhancement in T1-weighted images was observed in the normal liver and pancreatic parenchyma after infusion of MnDPDP at doses of 5 and 10 μmol/kg. The maximal enhancement in the two dose groups was 77 and 110% in the liver, and 57 and 84% in the pancreas, respectively. The enhancement-over-time profiles demonstrated that the effective imaging window was about 2 h for the liver, and over 4 h for the pancreas. There was no measurable enhancement in brain structures protected by intact blood-brain barrier, and no changes of clinical importance were found in vital signs or in blood and urinary chemistry variables.Compared with unenhanced images (including T2-weighted images), significantly more lesions were detected, on MnDPDP-enhanced T1 images in 82 patients with liver tumors (mostly metastases). Features such as rim enhancement and the enhancement in hepatocellular carcinomas can provide information for differential diagnosis.In a study on patients with pancreatic tumors, mainly adenocarcinomas (n=21) and islet cell tumors (n=19), two additional lesions were found in the MnDPDP-enhanced images. The contrast enhancement in the pancreatic parenchyma can vary greatly, depending on the site of the enhancingpart of the organ in relation to a large tumor. The tumors of both origins were also enhanced post-contrast, but to a lesser degree than the normal pancreatic tissue.MnDPDP enhancement was investigated in 30 liver metastases from endocrine tumors in 13 patients. These lesions showed a signal increase of about 49% post-contrast, which lasted longer than that in the normal liver tissue. The findings may help to distinguish these tumors from other metastatic tumors.T1-weighted sequences of four types, including a spin-echo and three variants of fast gradient-echo sequences, and various parameter combinations, were investigated in healthy volunteers (n=6), with the aim of finding the optimal sequence for MnDPDP-enhanced MRI of the liver andpancreas. The fat-and-water out-of-phase, fast field (gradient)-echo sequence was the best for imaging of both the liver and pancreas.The studies have shown that MnDPDP is safe when given as an infusion and is effective as a liver- and pancreas-specific contrast medium, with improved lesion detection in MRI of these organs. It is also useful for the characterization of liver tumors.
|
|
| 15. |
- Wang, Chen, et al.
(författare)
-
MRI multiplanar reconstruction in the assessment of congenital talipes equinovarus
- 1999
-
Ingår i: Pediatric Radiology. - : Springer Science and Business Media LLC. - 0301-0449 .- 1432-1998. ; 29:4, s. 262-267
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Magnetic resonance imaging (MRI) has been shown to be a useful tool in the evaluation of the complex deformities which are present in congenital talipes equinovarus (clubfoot). OBJECTIVE: To evaluate MRI with the multiplanar reconstruction (MPR) technique as a new method for assessment of clubfoot. MATERIALS AND METHODS: Seven infants with 11 clubfeet were studied by using three-dimensional gradient-echo MR sequences. MPR was performed from the acquired image data in orthogonal, single and double oblique planes to demonstrate the complex deformities in clubfoot. Three angles (talar body-neck angle, talocalcaneal left-right angle and the talocalcaneal superior-inferior angle) were defined for measuring the medial angulation of the talar neck and the rotation of the calcaneus in relation to the talus. RESULTS: The method clearly demonstrated the pathological anatomy of the clubfeet, especially the talonavicular articulations. Dislocation of the navicular bone was observed in 9 of the 11 feet. The angle measurements were easily conducted with MPR, and these angles differed considerably among the patients. CONCLUSIONS: The information provided by this method is useful for classification of the severity of clubfoot deformities.
|
|
| 16. |
- Wang, Chen, et al.
(författare)
-
Sequence optimization in mangafodipir trisodium-enhanced liver and pancreas MRI
- 1999
-
Ingår i: Journal of Magnetic Resonance Imaging. - 1053-1807 .- 1522-2586. ; 9:2, s. 280-284
-
Tidskriftsartikel (refereegranskat)abstract
- To find an optimal magnetic resonance (MR) sequence for mangafodipir trisodium-enhanced liver and pancreas imaging, six healthy volunteers were studied using a 1.5 T MR system with different T1-weighted abdominal imaging sequences. These were turbo field (gradient)-echo (TFE), fast field (gradient)-echo (FFE), and spin-echo sequences before and after mangafodipir trisodium administration. Various parameter combinations were investigated within each sequence type, and then the best combination was found and compared with those of the other sequences. Signal intensity (SI) measurements were made in regions of interest in the liver, pancreas, and a reference marker with a known T1 value. Contrast index (CI, SItissue/SImarker) and contrast-to-noise ratio (CNR, [SItissue/SImarker]/SDbackground) were calculated, and percentage CI increase and CNR in the postcontrast images were used for the best sequence evaluation. Regarding CI, the TFE sequence with a TR/TE/flip angle of 15 msec/4.6 msec/20 degrees and inversion time of 300 msec had the largest pre- to postcontrast percentage increase. The FFE sequence with a TR/TE/flip angle of 140 msec/4.6 msec/90 degrees had the highest postcontrast CNR and is considered to be the optimal sequence for mangafodipir trisodium-enhanced MR imaging of the liver and pancreas.
|
|
| 17. |
|
|
| 18. |
- Wang, Chen, et al.
(författare)
-
Uptake of mangafodipir trisodium in liver metastases from endocrine tumors
- 1998
-
Ingår i: Journal of Magnetic Resonance Imaging. - 1053-1807 .- 1522-2586. ; 8:3, s. 682-686
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of the study was to investigate retrospectively whether mangafodipir trisodium (MnDPDP) can enhance the liver metastases from endocrine tumors. Thirteen patients with endocrine tumors and liver metastases underwent T1-weighted spin-echo (SE) and turbo gradient-echo (GRE) MRI conducted before and 20 to 60 minutes after i.v. infusion of MnDPDP. Additional 24-hour-delay scans were performed in 8 of 13 patients. MR signal intensity (SI) was measured in liver parenchyma and metastases, which was then related to that of paraspinal muscle. A total of 30 lesions on precontrast and postcontrast images and 18 lesions on 24-hour-delay images were measured. An enhancement by 49% in SE and 40% in GRE images (P = .0001) was observed in tumor tissues after MnDPDP infusion. In 24-hour-delay images, the SI of the lesions remained relatively high, but in liver parenchyma, it decreased significantly, and the tumor-liver tissue contrast was reduced.
|
|
| 19. |
|
|
| 20. |
|
|
| 21. |
|
|
| 22. |
- Wang-Chen, Ke
(författare)
-
Transformation and Symbolic Calculations in Filtering and Control
- 1994
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with several aspects of optimal control and filtering problems. A fundamental problem in the optimal control theory is the design of a regulatorfora linear system which minimizes a quadratic cost function characterizing the control effort and the deviations of the system from the ideal operation. On the other hand, a basic problem in signal analysis is the optimal estimation of a useful signal from observations corrupted by additive noise. The solutions of both problems depend in a crucial way on solutions of the matrix Riccati differential equation.This work is an effort to unify the theoretical analysis and the numerical or symbolic calculation of solutions of the Riccati differential equation (RDE) as well as the algebraic Riccati equation (ARE) via a matrix transformation. It is shown that the most important issues evolving around the Riccati equation solution can be completely chara:cterized by submatrices of a transformation matrix. Not only the necessary and sufficient conditions for the existence of a solution but also an explicit expression of the solution are obtained from this computable matrix transformation. The transformation matrix can be calculated whether the solution exists or not. It can clearly be seen from this transformation matrix that the solution of the ARE can be explicitly expressed via the submatrices even if the system is not stabilizable (in the optimal filtering context). Furthermore, the Riccati differential equation can also be solved analytically in terms of these submatrices. The criterion, which ensures a solution of the Riccati differential equation to converge to the stabilizing solution, or the strong solution, are established via the same transformation matrix and with a more relaxed requirement on the initial condition than existing results. The criterion is proven to be sufficient and necessary, thus extending existing convergence results.The technique of the matrix transformation is shown to be very useful for exploring the Riccati equation associated with linear time varying systems. We show that an important class of linear time varying systems can be transformed using an appropriate time varying matrix transformation to a linear time invariant form. Hence, instead of attempting to solve the RDE with time varying coefficients, its time invariant correspondence may be solved symbolically.In applying the theoretical analysis for practical systems, a central question is how well-established theories for linear systems can be applied to practical nonlinear systems. As an effort to bridge the gap, we extend linear optimal filtering to some nonlinear problems. The technique proposed in the thesis is applied to solve the problem of transformer saturation in protective relaying for power systems. Simulation results are provided to illustrate the accuracy of the method.
|
|
| 23. |
- Wang, Feiyue, et al.
(författare)
-
Modeling Sorption of Trace Metals on Natural Sediments by Surface Complexation Model
- 1997
-
Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 31:2, s. 448-453
-
Tidskriftsartikel (refereegranskat)abstract
- The potential possibility of the surface complexation models to describe the sorption of trace metals on natural sediments has been suggested since the late 1980s, which should be of natural importance to predict the bioavailability of trace metals in aquatic sediments. This possibility was tested based on 11 geographically and hydrologically diverse natural aquatic sediment samples. The sorption of Cu(II), Zn(II), Pb(II), and Cd(II) on these sediments was studied by both sorption isotherm and pH-edge sorption experiments. The experimental sorption data were fit well by the surface complexation model (the double-layer model). The linear free energy relationship (LFER) between the surface complexation constants (Ks) of trace metals on the sediments and the corresponding first-hydrolysis constants (*K1) was observed, which could be expressed as log Ks = a log *K1 + b. The slope of the linear regression, a, was dependent on the sediment composition: a = 0.19TOC - 0.09Oxides + 1.31 (n = 11), where TOC (%) is the total organic carbon and Oxides (%) include reactive iron oxide, amorphous iron oxide, cryptocrystalline manganese oxide, and aluminum oxide. The results strongly suggest that the sorption of trace metals on natural sediments could be described reasonably by the surface complexation model and predicted potentially from the relationships between Ks and *K1 and the sediment composition.
|
|
| 24. |
|
|
| 25. |
|
|
| 26. |
|
|
| 27. |
|
|
| 28. |
|
|
| 29. |
|
|
