Showing papers by "University of Macau published in 1994"

Microstructure of SnO2.

Abstract: The microstructure of ${\mathrm{SnO}}_{2}$, prepared by the sol-gel method, was studied by scanning electron microscopy, transmission electron microscopy, high-resolution electron microscopy, and x-ray diffraction. A nanosponge structure was observed. There is much surface and interface structure. The interfaces vary in type from amorphous to crystalline. The high density of defects greatly influences the physical and chemical properties of this material.

Yanhusuo extract inhibits metastasis of breast cancer cells by modulating mitogen-activated protein kinase signaling pathways.

Abstract: Yanhusuo (Corydalis yanhusuo W.T. Wang) is a well-known traditional Chinese medicine (TCM). In this study, we attempted to characterize in detail the signaling cascades that produce its anti-metastatic effect on the human breast cancer cell line, MDA-MB-231. We found that the yanhusuo extract inhibited the migration and invasion of MDA-MB-231 cells in vitro. In addition, the yanhusuo extract inhibited the mRNA expression and activity of metalloproteinase-9 (MMP-9). The anti-cancer metastasis effect of yanhusuo involved the activation of p38 and inhibition of ERK1/2 and SAPK/JNK mitogen-activated protein kinase (MAPK) signaling. Our experiments identified the biological activity of yanhusuo against cancer metastasis in vitro and provide a rationale for its further investigation.

A Comparison Between the Rating Scale Model and Dual Scaling for Likert Scales

Abstract: The fundamental requirement of using Likert scales to measure affective behaviors - that all respondents must use the ordered response categories of all scale statements in the same way - is examined. Scaling problems arise when attitude statements within a Likert scale are unfolding preference data, and when the position and spacing of the ordered response categories are interpreted differently across scale statements and among respondents. The assignment of a neutral response category in the center of the response scale is questionable. These problems pertain to issues of the existence of an interval scale, the dimensionality of the trait, and patterns of item response functions. An attempt is made to resolve these problems using two contrasting scaling methods - item response theory modeling and dual scaling

Hartley preconditioners for Toeplitz systems generated by positive continuous functions

Abstract: In this paper, we consider the solution ofn-by-n symmetric positive definite Toeplitz systemsT n x=b by the preconditioned conjugate gradient (PCG) method. The preconditionerM n is defined to be the minimizer of ‖T n −B n ‖ F over allB n eH n whereH n is the Hartley algebra. We show that if the generating functionf ofT n is a positive 2π-periodic continuous even function, then the spectrum of the preconditioned systemM n −1 T n will be clustered around 1. Thus, if the PCG method is applied to solve the preconditioned system, the convergence rate will be superlinear.

Urbanization and its effects on the ecology of mosquitoes in Macau, Southeast Asia.

Abstract: Recent urbanization in Macau has resulted in the precipitous decline to zero in populations of several anopheline vectors of malaria while providing optimal habitat for the population increase in culicines. Of 18 species of mosquitoes reported in Macau in recent years, 15 species are included here. Culex quinquefasciatus, Culex sitiens, and Aedes albopictus were the most abundant species. Notes are provided for Anopheles sinensis, Armigeres magnus, Armigeres subalbatus, Culex foliatus, Culex fuscanus, Culex infantulus, Culex rubithoracis, Culex sumatranus, Culex tritaeniorhynchus, Mansonia uniformis, Toxorhynchites splendens, and Tripteroides sp.

The asean free trade area implications for indonesia's imports

Abstract: The Singapore Declaration of 1992, announcing the establishment of an ASEAN Free Trade Area (AFTA), effectively brings down tariff levels on intra-ASEAN trade to 0–5% by the year 2008. This paper estimates the changes in Inonesia's imports that will result from trade creation generated by AFTA. Our results show that Indonesia's imports from other ASEAN partners will increase by 6%, based on 1990 figures. This is far greater than the estimated effects of the existing PTA scheme. However, these results are upper- bound estimates and include only static changes.

The study on conduction of fetal ECG by mathematical multi-layer model

Abstract: One of the most difficult problems is how to find the proper electrode positions on maternal abdomen from which the optimal fetal ECG can be obtained for perinatal monitoring. For this, a study on volume conduction of fetal ECG between source and the maternal abdomen by mathematical multi-layer model was carried out. FECG Potential distribution analysis on fetal vernix caseosa instead of current dipole was presented. A suitable finite clement method was designed for calculation. The result of a clinical case indicated that the potential distribution analysis on fetal vernix caseosa is meaningful.

On the decomposable numerical range of λI-N

Abstract: Let N be an nxn normal matrix. For 1≤m≤n we characterize the convexity of the mth decomposable numerical range of λIn -N which is defined to be {det(X∗(λIn −N)X) [sdot] X∊C n×m X ∗ X=Im }. A related problem on mixed decomposable numerical range of λIn -N is also discussed.

A note on best conditioned preconditioners

Abstract: We discuss the solution of Hermitian positive definite systemsAx=b by the preconditioned conjugate gradient method with a preconditionerM. In general, the smaller the condition numberκ(M −1/2 AM −1/2 ) is, the faster the convergence rate will be. For a given unitary matrixQ, letM Q = {Q*Λ N Q | Λ n is ann-by-n complex diagonal matrix} andM + ={Q*Λ n Q | Λ n is ann-by-n positive definite diagonal matrix}. The preconditionerM b that minimizesκ(M −1/2 AM −1/2 ) overM + is called the best conditioned preconditioner for the matrixA overM + . We prove that ifQAQ* has Young's Property A, thenM b is nothing new but the minimizer of ‖M −A‖ F overM Q . Here ‖ · ‖ F denotes the Frobenius norm. Some applications are also given here.

Knowledge-based sub-pattern segmentation: decompositions of Chinese characters

Abstract: Chinese characters are complex two-dimensional patterns. Although radicals are the most significant components in Chinese characters, it is difficult to extract them from the characters because radicals are often interlaced and connected to each other and, consequently, histogram-based segmentation methods fail to separate them. We propose to segment the interlaced parts in the images by a skeletonization algorithm based on contour tracing. To separate further connected parts of the Chinese characters we suggest a new processing method resorting to the knowledge of the radical connections and the structure of the characters. The separation repeats until all the disconnected parts cannot be segmented further conforming to our knowledge-based criterion. >

Some geometrical properties of the decomposable numerical range

Abstract: For 1≤m≤n, the mth decomposable numerical range of an nxn complex matrix A is defined and denoted by In this note, we determine the conditions on as essentially Hermitian matrix A(i.e.A is normal with colliner eigenvalues) such that is (i) convex, or (ii) simply connected. For a general A, we obtain a sufficient condition for to be starshaped. These answer some questions raised by Bebiano and the second author on the geometrical properties of the decomposable numerical range.