Showing papers by "Sun Yat-sen University published in 2000"

Palaeovegetation of China: a pollen data‐based synthesis for the mid‐Holocene and last glacial maximum

Abstract: Pollen data from China for 6000 and 18,000 C-14 yr BP Were compiled and used to reconstruct palaeovegetation patterns, using complete taxon lists where possible and a biomization procedure that entailed the assignment of 645 pollen taxa to plant functional types. A set of 658 modern pollen samples spanning all biomes and regions provided a comprehensive test for this procedure and showed convincing agreement between reconstructed biomes and present natural vegetation types, both geographically and in terms of the elevation gradients in mountain regions of north-eastern and south-western China. The 6000 C-14 yr BP map confirms earlier studies in showing that the forest biomes in eastern China were systematically shifted northwards and extended westwards during the mid-Holocene. Tropical rain forest occurred on mainland China at sites characterized today by either tropical seasonal or broadleaved evergreen/warm mixed forest. Broadleaved evergreen/warm mixed forest occurred further north than today, and at higher elevation sites within the modern latitudinal range of this biome. The northern limit of temperate deciduous forest was shifted c. 800 km north relative to today. The 18,000 C-14 yr BP map shows that steppe and even desert vegetation extended to the modem coast of eastern China at the last glacial maximum, replacing today's temperate deciduous forest. Tropical forests were excluded from China and broadleaved evergreen/warm mixed forest had retreated to tropical latitudes, while taiga extended southwards to c. 43 degreesN.

Embedding image watermarks in dc components

Abstract: Both watermark structure and embedding strategy affect robustness of image watermarks. Where should watermarks be embedded in the discrete cosine transform (DCT) domain in order for the invisible image watermarks to be robust? Though many papers in the literature agree that watermarks should be embedded in perceptually significant components, dc components are explicitly excluded from watermark embedding. In this letter, a new embedding strategy for watermarking is proposed based on a quantitative analysis on the magnitudes of DCT components of host images. We argue that more robustness can be achieved if watermarks are embedded in dc components since dc components have much larger perceptual capacity than any ac components. Based on this idea, an adaptive watermarking algorithm is presented. We incorporate the feature of texture masking and luminance masking of the human visual system into watermarking. Experimental results demonstrate that the invisible watermarks embedded with the proposed watermark algorithm are very robust.

Hydrothermal synthesis and crystal structures of three-dimensional co-ordination frameworks constructed with mixed terephthalate (tp) and 4,4′-bipyridine (4,4′-bipy) ligands: [M(tp)(4,4′-bipy)] (M = CoII, CdII or ZnII)

Abstract: Three new metal–organic co-ordination frameworks formulated as [M(tp)(4,4′-bipy)] [M = CoII1, CdII2 or ZnII3; tp = terephthalate; 4,4′-bipy = 4,4′-bipyridine] have been hydrothermally prepared and structurally characterized. Each pair of metal atoms in the three compounds are bridged by bis-bidentate or chelating/bridging bis-bidentate tp ligands to form a linear or zigzag co-ordination chain, and adjacent chains are further linked by chelating or monodentate bis-bidentate tp ligands to form two-dimensional rectangular or parallelogram-like [M(tp)] sheets with dimensions of 10.30 × 11.37, 10.08 × 11.68 and 10.28 × 10.98 A for complexes 1, 2 and 3, respectively. Adjacent sheets are pillared by 4,4′-bipy spacers into a three-dimensional co-ordination network through the covalently linking mode of ⋯4,4′-bipy–MII–4,4′-bipy–MII⋯, which feature cuboidal [M16(tp)8(4,4′-bipy)8] structural units. Twofold interpenetration of the above three-dimensional co-ordination networks results in stable crystal structures of the three compounds.

Molecular ladders with multiple interpenetration of the lateral arms into the squares of adjacent ladders observed for [M2(4,4'-bpy)3(H2O)2(phba)2] (NO3)(2).4H2O (M = Cu2+ or Co2+; 4,4'-bpy = 4,4'-bipyridine; phba = 4-hydroxybenzoate).

Abstract: Two isomorphous molecular ladders formulated as [M2(4,4‘-bpy)3(phba)2(H2O)2](NO3)2·4H2O (4,4‘-bpy = 4,4‘-bipyridine; phba = 4-hydroxybenzoate; M = Cu2+ or Co2+), shown by X-ray, feature a novel ladder motif having different inner rungs (4,4‘-bpy) and lateral arms (phba). Penetration of the lateral arms into the squares of adjacent ladders results in a novel 3-D network.

The Influence of Hedonic Values on Consumer Behaviors: An Empirical Investigation in China

Abstract: Summary This study investigated the influence of hedonic values on the consumer behavior of young Chinese. The results show that hedonic values are negatively associated with utilitarian orientation and positively associated with novelty seeking, responsiveness to promotion stimuli, and preference for foreign brands. Personal income moderates the relationship between hedonic values and brand consciousness. Conceptual importance and managerial implications are discussed.

Recurrent chromosome alterations in hepatocellular carcinoma detected by comparative hybridization

Abstract: Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and has a very poor prognosis. Fifty primary HCC cases have been analyzed in the present study to explore the association between genomic alteration in primary HCC and clinical features. Several recurrent chromosomal abnormalities were identified in this study. The most frequently detected chromosomal gains involved chromosome arms 1q (33/50 cases, 66%), 8q (24/50 cases, 48%), and 20q (10/50 cases, 20%). High‐copy‐number amplifications involving 1q (4 cases), 8q (3 cases), and 20q (3 cases) were detected, and a minimum overlapping amplified region at 1q12–q22 was identified. The most frequently detected loss of chromosomal material involved 16q (35/50 cases, 70%), 17p (26/50 cases, 52%), 19p (21/50 cases, 42%), 4q (20/50 cases, 40%), 1p (18/50 cases, 36%), 8p (16/50 cases, 32%), and 22q (14/50 cases, 28%). The associations between genomic alterations detected in the present study and clinical features including clinical stage, tumor size, HBV infection, chronic liver disease, and liver cirrhosis were explored. Our CGH results suggest that the gain of 20q and deletion of 8p are late genetic alterations in HCC, because the incidence of these alterations was obviously increased in the advanced clinical stages. Another finding showed that loss of 8p and gain of 8q and 20q are associated with tumor size. The recurrent gain and loss of chromosomal regions identified in this study provide candidate regions that may contain oncogenes or tumor suppressor genes respectively involved in HCC development and progression. © 2000 Wiley‐Liss, Inc.

Regulation of TNF Expression by Multiple Mitogen-Activated Protein Kinase Pathways

Abstract: Stimulating macrophages with bacterial endotoxin (LPS) activates numerous intracellular signaling pathways that lead to the production of TNF. In this study, we show that four mitogen-activated protein (MAP) kinase pathways are activated in LPS-stimulated macrophages: the extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase/stress-activated protein kinase, p38, and Big MAP kinase (BMK)/ERK5 pathways. Although specific activation of a single MAP kinase pathway produces only a modest effect on TNF promoter activation, activation of each MAP kinase pathway is important for full induction of the TNF gene. Interestingly, a dramatic induction of TNF promoter-driven gene expression was observed when all of the four MAP kinase pathways were activated simultaneously, suggesting a cooperative effect among these kinases. Unexpectedly, cis elements known to be targeted by MAP kinases do not play a major role in multiple MAP kinase-induced TNF gene expression. Rather, a 40-bp sequence harboring the TATA box, is responsible for the gene up-regulation induced by MAP kinases. The proximity of the MAP kinase-responsive element to the transcriptional initiation site suggested that MAP kinases regulate the transcriptional initiation complex. Utilizing α-amanitin-resistant RNA polymerase II mutants with or without a C-terminal domain (CTD) deletion, we found that deleting the CTD to 31 tandem repeats (Δ31) led to >90% reduction in MAP kinase-mediated TNF production. Thus, our data demonstrate coordination of multiple MAP kinase pathways in TNF production and suggest that the CTD of RNA polymerase II is required to execute MAP kinase signaling in TNF expression.

Self-assembly of two- and three-dimensional coordination networks with hexamethylenetetramine and different silver(I) salts

Abstract: Interesting two-dimensional networks with square or hexagonal cavities, and three-dimensional networks with different channels, have been obtained by varying the counterions, the molar ratio of metal to hmt (hmt = hexamethylenetetramine) and the pH values of the initial solutions Among the eleven products isolated and structurally characterized, two have a metal-to-hmt molar ratio of 2:1 and are the first examples of Ag-hmt square networks, namely [Ag2(mu4-hmt)(NO2)2] (1) and [Ag2(mu4-hmt)(SO4)(H2O)]4H2O (2), two have a metal-to-hmt molar ratio of 1:1 and are 2-D networks with hexagonal cavities, namely [Ag(micro3-hmt)(NO2)] (3) and [Ag2(micro3-hmt)2](S2O6)2H2O (4), and seven present the metal-to-hmt molar ratios of 3:1, 2:1, 3:2, or 4:3 and are 3-D networks of novel topologies and with different channels, namely [Ag2(mu4-hmt)(micro4-ox)] (5), [Ag3(micro4-hmt)2(H2O)2](SO4)(HSO4) 2H2O (6), [Ag2(mu4-hmt)(mu2-O2CMe)](MeCO2)45 H2O (7), [Ag2(mu4-hmt)(mu3-maleate)]5H2O (8), [Ag3(mu4-hmt)(mu2-O2CPh)3] (9), [Ag4(mu4-hmt)3(H2O)](SO4)(NO3)23H2O (10), and [Ag12(mu4-hmt)6(mu3-HPO4)(mu2-H2PO4)3(H2PO4)7(H2O)](H3PO4)105H2O (11)

C-supplemented subgroups of finite groups

Abstract: A subgroup H of a group G is said to be c-supplemented in G if there exists a subgroup K of G such that HKa G and H\ K is contained in CoreGOHU .W e follow Hall's ideas to characterize the structure of the finite groups in which every subgroup is c-supplemented. Properties of c-supplemented subgroups are also applied to determine the structure of some finite groups.

Two-photon pumped lasing stilbene-typechromophores containing various terminal donor groups: relationship betweenlasing efficiency and intramolecular charge transfer

Abstract: A series of new two-photon pumped (TPP) up-conversion lasing dyes, named as CSPI, DPASPI, PSPI, DEASPI and HEASPI respectively, have been synthesized. These dyes are stilbene-type chromophores end-capped with the same acceptor group but with varied donor groups, whose different electron-donating abilities can be ordered by 1H NMR chemical shift data. PM3 calculations show that attaching different donors changes the bond length alternation (BLA) and charge density distribution of the styrylpyridine skeleton. These chromophores exhibit different two-photon up-conversion emission behavior. Pumped by a 1064 nm, ∼40 ps mode-locked Nd ∶ YAG laser pulses, all chromophores showed two-photon pumped (TPP) up-conversion laser emission, but the efficiencies showed a difference of about two orders of magnitude, ranging from an up-conversion efficiency of 10.7% for DEASPI to 0.13% for CSPI under the same experimental conditions. The results show that the efficiency of two-photon pumped emission is related to the intramolecular charge transfer character of the chromophore. The two-photon pumped lasing efficiency increases both with decreasing BLA and with increasing intramolecular charge transfer character, measured by the parameter Δρ1,2.

Enantiomeric ruthenium(II) complexes binding to DNA: binding modes and enantioselectivity.

Abstract: A series of enantiomerically pure polypyridyl ruthenium(II) complexes, delta- and lambda-[Ru(bpy)2 (HPIP)](PF6)2 (delta-1 and lambda-1; bpy=2,2'-bipyridine, HPIP = 2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline), delta and lambda-[Ru(bpy)2(HNAIP)](PF6)2 (delta-2 and lambda-2; HNAIP = 2-(2-hydroxy-1-naphthyl)imidazo[4,5-f][1,10]phenanthroline), delta- and lambda-[Ru(bpy)2 (HNOIP)](PF6)2 (delta-3 and lambda-3; HNOIP = 2-(2-hydroxy-5-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline), and delta- and lambda-[Ru(bpy)2(DPPZ)](PF6)2 (delta-4 and lambda-4; DPPZ= dipyridophenazine), have been synthesized. Binding behavior of these chiral complexes to calf thymus DNA (CT-DNA) has been investigated by electronic absorption, steady-state emission, and circular dichroism spectroscopies, as well as by viscosity measurements and equilibrium dialysis binding studies. Several points came from the results. (1) The DNA-binding properties were distinctly different for the [Ru(bpy)2L]2+ (L=HPIP, HNAIP, HNOIP) series of ruthenium(II) complexes, which indicates that the photophysical behavior of the complexes on binding to DNA can be modulated through ligand design. (2) Different binding rates of individual enantiomers of complexes 1 and 4 to DNA were observed through dialysis experiments. The lambda enantiomer bound more rapidly than the lambda enantiomer and their different intercalative binding geometries were suggested to be responsible. (3) Both delta-2 and lambda-2 bound weakly to CT-DNA; delta-2 may bind through a partial intercalation mode, whereas lambda-2 may bind in the DNA groove. (4) There was no noticeable enantioselectivity for complexes 1, 3, and 4 on binding to CT-DNA. Both of their enantiomers can intercalate into DNA base pairs. It is noted that delta-3 and lambda-3 exhibited almost identical spectral changes on addition of CT-DNA, and a similar binding manner of the isomers to the double helix was proposed.

Gromov-Witten invariants of blow-ups along points and curves

Abstract: In this paper, using the gluing formula of Gromov-Witten invariants under symplectic cutting, due to Li and Ruan, we studied the Gromov-Witten invariants of blow-ups at a smooth point or along a smooth curve We established some relations between Gromov-Witten invariants of M and its blow-ups at a smooth point or along a smooth curve

Hydrothermal synthesis and crystal structure of a layered vanadium oxide with an interlayer metal co-ordination complex: Cd[C3N2H11]2[V8O20]

Abstract: The compound Cd[C3N2H11]2[V8O20] was synthesized from the hydrothermal reactions of V2O5, CdSO4, 1,2-diaminopropane (enMe) and water in the molar ratio 1∶1∶2.2∶223. Its structure has been determined by single-crystal X-ray diffraction. This compound has an open three-dimensional framework structure consisting of [V8O20]4− layers, composed of equal numbers of VO4 tetrahedra and VO5 pyramids connected by both corner and edge sharing. The Cd[enMeH]24+ complex occupies the interlayer space and connects with the vanadium oxide layers through four Cd–O bonds. This arrangement gives one-dimensional channels with 10-membered rings along the c axis.

Genome-wide allelotype analysis of sporadic primary nasopharyngeal carcinoma from southern China.

Abstract: Nasopharyngeal carcinoma (NPC) is one of the most common malignant tumors in Southern China, especially in the Guangdong area. To demonstrate a comprehensive profile of loss of heterozygosity (LOH) in NPC, we applied a large panel of 382 microsatellite polymorphism markers covering all the 22 autosomes in 98 cases of sporadic primary NPC. Of the 335 informative markers, 83 loci showed high level of LOH (presence in equal to or more than 30% cases) and most of the high frequent loci were clustered to chromosome 1p36 and 1p34, 3p14-p21, 3p24-p26, 3q25-q26 and 3q27, 4q31 and 4q35, 5q15-21 and 5q32-q33, 8p22-p23, 9p21-p23 and 9q33-q34, 11p12-p14, 13q14-q13 and 13q31-q32, 14q13-q11, 14q24-q23 and 14q32. High frequency of LOH was found in chromosomes 3, 5, 9 and 11 (>/=50%), while medium frequency of LOH was found in chromosomes 1, 4, 6, 14, 17 and 19 (40-49%). Several new regions showing high frequency of LOH were found in chromosome 1p36, 3q25-q26, 3q27, 5q15-q21, 8p22-p23 and 11p12-14. The relationship between LOH and TNM stage of NPC was evaluated. Regions 6p23 (D6S289), 8p23.1 (D8S549) and 9q34.2 (D9S1826) showed higher frequency of LOH in later stages (III and IV) than in earlier stages (I and II) (P<0.05). Thus, our study provides a global view on allelic loss in the development of NPC and should shed light on the way for localization of putative tumor suppressor genes associated with the pathogenesis of NPC.

Characterization of Dirac-structure edges with wavelet transform

Abstract: This paper aims at studying the characterization of Dirac-structure edges with wavelet transform, and selecting the suitable wavelet functions to detect them. Three significant characteristics of the local maximum modulus of the wavelet transform with respect to the Dirac-structure edges are presented: (1) slope invariant: the local maximum modulus of the wavelet transform of a Dirac-structure edge is independent on the slope of the edge; (2) grey-level invariant: the local maximum modulus of the wavelet transform with respect to a Dirac-structure edge takes place at the same points when the images with different grey-levels are processed; and (3) width light-dependent: for various widths of the Dirac-structure edge images, the location of maximum modulus of the wavelet transform varies lightly under the certain circumscription that the scale of the wavelet transform is larger than the width of the Dirac-structure edges. It is important, in practice, to select the suitable wavelet functions, according to the structures of edges. For example, Haar wavelet is better to represent brick-like images than other wavelets. A mapping technique is applied in this paper to construct such a wavelet function. In this way, a low-pass function is mapped onto a wavelet function by a derivation operation. In this paper, the quadratic spline wavelet is utilized to characterize the Dirac-structure edges and a novel algorithm to extract the Dirac-structure edges by wavelet transform is also developed.

Revegetation of Pb/Zn Mine Tailings, Guangdong Province, China

Abstract: The Lechang lead/zinc mine is located in the north part of Guangdong Province, southern China. The tailings residue from the extraction of lead/zinc ores was permanently stored in tailings ponds, which required revegetation to reduce the environmental impact. A field study was, therefore, conducted to evaluate the effects of different ameliorants, including: (1) pig manure (PM); (2) mushroom compost (MC); (3) burnt coal residue (BC); (4) fly ash (FA); and (5) surface soil on the growth of Agropyron elongatum (tall wheat grass), Cynodon dactylon (Bermuda grass), Lolium multiflorum (Italian ryegrass), and Trifolium repens (clover) in the tailings residue. The results from the core profiles indicated that adding FA (10 cm) or BC (15 cm) as a barrier layer between the cover soil and the tailings could increase pH, compared to the treatment with soil only. C. dactylon grew well and had a high cover (90‐100%) in all the treatment plots except the control plots without any amendment. A. elongatum and L. multiflorum had a higher cover when grown in plots covered with a barrier layer using FA or BC (both with surface soil), than those grown in plots covered with surface soil only. Treatment plots receiving a thicker soil cover (30 cm) had a better dry weight yield than those with a thinner soil cover (15 cm), regardless of the barrier layer. The results from this study indicate that the use of either 15 cm BC or 10 cm FA as a barrier layer with surface soil, or the use of 38 tonnes PM/ha and 6 cm MC, were effective for the revegetation of Pb/Zn mine tailings. C. dactylon was the best species among the four species used for revegetation.

Organic–inorganic hybrid materials assembled through weak intermolecular interactions. Synthesis, structures and non-linear optical properties of [4,4′-bipyH2][M(NCS)4] (M = Mn2+, Co2+ or Zn2+; 4,4′-bipy = 4,4′-bipyridine)

Abstract: Three compounds [4,4′-bipyH2][M(NCS)4] (M = Mn2+, Co2+ or Zn2+; 4,4′-bipy = 4,4′-bipyridine) were obtained from the reactions of 4,4′-bipy with M(SCN)2 in acidic solution and their crystal structures determined by single-crystal X-ray diffraction. All crystallise isomorphously in the chiral orthorhombic space group P21212. The tetrahedral [M(NCS)4]2− anions are inter-connected by S⋯S contacts (ca. 3.63 A) and are hydrogen bonded with the diprotonated [4,4′-bipyH2]2+ cations [N⋯S 3.241 A in 1; 3.235 A in 2; 3.239 A in 3] to form two-dimensional, highly wavy networks with hourglass-shaped cavities (ca. 12.3 A long; 9.4 A wide at the ends, 6.8 A at the waist). These two-dimensional networks are stacked with each other to furnish a channel accommodating the diprotonated [4,4′-bipyH2]2+ cations. The three organic–inorganic hybrid compounds are thermally stable with melting points above 230 °C. The powder second harmonic generation efficiencies were measured as moderate.

Complete Riemannian manifolds with pointwise pinched curvature

Abstract: An analogous Bonnet-Myers theorem is obtained for a complete and positively curved n-dimensional (n≥3) Riemannian manifold M n . We prove that if n≥4 and the curvature operator of M n is pointwise pinched, or if n=3 and the Ricci curvature of M 3 is pointwise pinched, then M n is compact.

Effect of silane-grafted polypropylene on the mechanical properties and crystallization behavior of talc/polypropylene composites

Abstract: Talc-filled polypropylene (PP) composites coupled with silane-grafted polypropylene (PP-g-Si) were prepared. Effect of PP-g-Si on the mechanical properties, crystallization, and melting behavior of PP composites was investigated. Compared with the uncoupled composites, the mechanical properties of Talc/PP composites coupled with a small amount of PP-g-Si were increased to some extent. Meanwhile, PP-g-Si can promote crystallization rate and increase crystallization temperature of PP in the composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2974–2977, 2000

On geometric and orthogonal moments

Abstract: Moments are widely used in pattern recognition, image processing, computer vision and multiresolution analysis. To clarify and to guide the use of different types of moments, we present in this paper a study on the different moments and compare their behavior. After an introduction to geometric, Legendre, Hermite and Gaussian-Hermite moments and their calculation, we analyze at first their behavior in spatial domain. Our analysis shows orthogonal moment base functions of different orders having different number of zero-crossings and very different shapes, therefore they can better separate image features based on different modes, which is very interesting for pattern analysis and shape classification. Moreover, Gaussian-Hermite moment base functions are much more smoothed, they are thus less sensitive to noise and avoid the artifacts introduced by window function discontinuity. We then analyze the spectral behavior of moments in frequency domain Theoretical and numerical analyses show that orthogonal Legendre and Gaussian-Hermite moments of different orders separate different frequency bands more effectively. It is also shown that Gaussian-Hermite moments present an approach to construct orthogonal features from the results of wavelet analysis. The orthogonality equivalence theorem is also presented. Our analysis is confirmed by numerical results, which are then reported.