Showing papers by "National University of Singapore published in 1989"
TL;DR: It is suggested that two methods for measuring a quantitative variable can be judged interchangeable provided all of the following conditions are met: first the methods must not exhibit marked additive or nonadditive systematic bias; second the difference between the two mean readings is not "statistically significant"; third, the lower limit of the 95% confidence interval of the intraclass correlation is at least 0.75.
437 citations
TL;DR: This paper found that the winner's curse is evident in allocation patterns used in Singapore and that the unseasoned new issues' anomaly disappears when the rationing associated with new issues is incorporated into the analysis.
316 citations
TL;DR: In this article, the distribution of xanthones is examined in relation to the taxonomic divisions of the Guttiferae, and various pharmacological properties of Xanthones are summarized.
305 citations
01 Sep 1989
TL;DR: In this paper, a general family of twisted actions of locally compact groups on C*-algebras and the corresponding twisted crossed product C *-algeses are discussed.
Abstract: Group algebras and crossed products have always played an important role in the theory of C*-algebras, and there has also been considerable interest in various twisted analogues, where the multiplication is twisted by a two-cocycle. Here we shall discuss a very general family of twisted actions of locally compact groups on C*-algebras, and the corresponding twisted crossed product C*-algebras. We shall then establish some of the basic properties of these algebras, motivated by the requirements of some applications we have in mind [2, 9, 10]. Some of our results will be known to others, at least in principle, but we feel that a coherent account might be useful.
281 citations
TL;DR: This paper applied Correspondence analysis to tourist perception data on Singapore and other Pacific Rim countries to improve Singapore's positioning in the tourism market and discussed how the Singapore Tourist Promotion Board can use the resulting output to improve the tourist market.
Abstract: Multinational tourism research involves analysis of multiple origins, multiple tourist destinations, and multiple attributes for destination selection . For example, tourist perceptions of a destination may vary across countries of origin. This can have important implications for which countries to target with tourism promotion, or which of the destination's attributes should be stressed in the promotion. Correspondence analysis is a technique which can handle problems of this complexity where other multiattribute analytical methods cannot. This technique is applied to empirical tourist perception data on Singapore and other Pacific Rim countries. A discussion of how the Singapore Tourist Promotion Board can use the resulting output to improve Singapore's positioning in the tourism market is presented.
274 citations
TL;DR: One of the important functions of the long head of the biceps is to stabilize the humeral head in the glenoid during powerful elbow flexion and forearm supination by the main muscle.
Abstract: The role of the tendon of the long head of the biceps in the stabilization of the head of the humerus was studied in 15 freely hanging anatomic specimen shoulders. Upward migration of the humeral head was measured by noting any reduction in the acromiohumeral distance in roentgenograms of the shoulder. There was a statistically significant decrease in the acromiohumeral interval on tensing the short head of biceps, but there was no significant change in the interval on tensing either the long head or both heads of the biceps brachii. Severing the tendon of the long head while both the heads were tensed caused a significant upward migration of the head of the humerus. One of the important functions of the long head of the biceps is to stabilize the humeral head in the glenoid during powerful elbow flexion and forearm supination by the main muscle. Sacrifice of the intraarticular segment of this tendon in surgical procedures of the shoulder may produce instability and dysfunction.
244 citations
TL;DR: In this article, the deconvoluted high-resolution N 1s core-level spectrum was used for quantitative determination of the proportion of benzoid amine, quinoid imine, and protonated units in chemically synthesized polyaniline.
Abstract: X-ray photoelectron spectroscopy (the deconvoluted high-resolution N 1s core-level spectrum in particular) was used for the quantitative determination of the proportion of benzoid amine, quinoid imine, and protonated units in chemically synthesized polyaniline. This method allows the tracking of structural changes during polyaniline oxidation and reduction.
222 citations
220 citations
TL;DR: It is suggested that the protective effects of certain dietary constituents, notably the cruciferous vegetables, may be more important than the hitherto stressed carcinogenic potential of fat and protein in the Asian population of countries of Southern and Eastern Asia newly undergoing industrialization.
Abstract: A hospital-based case-control study of diet and colorectal cancer was conducted among Chinese in Singapore (who constitute 77% of the population). A total of 203 cases and 425 controls were included. A history of the usual dietary intake one year prior to interview was taken using a quantitative food frequency questionnaire. Daily intakes of nutrients and selected food items were computed and stratified by tertiles of the control range, to assess risk in low-, medium- and high-intake categories. Effects were adjusted in analysis for age, sex, Chinese dialect group and occupation. For cancers of colon and rectum combined, significant observations were a protective effect of high cruciferous vegetable intake (OR = 0.50, p less than 0.01) and a predisposing effect of a high meat/vegetable consumption ratio (OR = 1.77, p less than 0.05). Similar results were observed for colon cancer alone. For rectal cancer alone (only 71 cases), significant (p less than 0.05) protective effects were observed for high intakes of protein (OR = 0.61), fibre (OR = 0.46), beta-carotene (OR = 0.54), cruciferous vegetables (OR = 0.51) and total vegetables (OR = 0.51). When further assessed by multiple logistic regression, tests for trend and assessment of risk in the extreme highest and lowest quintiles of the control range, the factors consistently significant were cruciferous vegetable intake and the meat/vegetable ratio. A particularly high relative risk was also noted in association with low coffee consumption (OR = 1.59, with p less than 0.05 for trend). No consistent trends were noted for fat or fibre intakes. For non-dietary variables investigated, a history of cholecystectomy increased the risk of both cancers combined (OR = 3.43, p less than 0.05) and colon cancer alone (OR = 4.39, p less than 0.01). This study in an Asian population of countries of Southern and Eastern Asia newly undergoing industrialization and in which rapid economic change is reflected in changing cancer patterns, suggests that the protective effects of certain dietary constituents, notably the cruciferous vegetables, may be more important than the hitherto stressed carcinogenic potential of fat and protein.
214 citations
TL;DR: In the long control region of the genome of the human papillomavirus type 16 (HPV-16) a DNA segment which functions as a cell-type-specific enhancer as well as mediating glucocorticoid response was identified in this article.
Abstract: We have previously identified in the long control region of the genome of human papillomavirus type 16 (HPV-16) a DNA segment which functions as a cell-type-specific enhancer as well as mediating glucocorticoid response. It contains multiple transcription-factor-binding sites, including several for nuclear factor I and one for the glucocorticoid receptor, which binds to the partially palindromic sequence TGTACANNNTGTCAT. We report here that this sequence element, when separated from the surrounding transcription-factor-binding sites and placed as an oligonucleotide into a test vector, retains its function as a glucocorticoid response element (GRE) in HeLa cells. In T47D cells, which express the progesterone receptor, the HPV-16 enhancer fragment mediates progesterone responsiveness. A point mutant in this fragment and the response of the oligonucleotide clone to both steroids prove the identity of the progesterone response element (PRE) with the GRE. The antiprogesterone and antiglucocorticoid RU486 interferes with both hormonal responses. In SiHa cells, the HPV-16 GRE mediates an increase in transcripts encoding E6 and E7 proteins, which are involved in transformation by HPV-16. Hormonal regulation is not restricted to HPV-16: DNA segments containing the cell-type-specific enhancers of HPV-11 and HPV-18 also mediate glucocorticoid and progesterone response. We identified sequence elements in the long control regions of HPV-11 and HPV-18 which function as GRE/PREs when tested as oligonucleotides. These findings suggest that GRE/PREs are an integral part of gene expression regulation in genital HPVs.
204 citations
TL;DR: It is clear that subcultured human ampullary cells support human embryonic cleavage and yield a reasonable number of good quality embryos up to the cavitation stage.
Abstract: Cultured human, ampullary, epithelial cells obtained from fertile women undergoing hysterectomy were evaluated for the support of human embryonic cleavage and growth in vitro. Twelve patients provided 23 embryos for co-culture with subcultured ampullary cells grown in T6 + 15% patient's serum and 18 embryos for growth in T6 + 15% patient's serum alone (controls). Of embryos co-cultured with ampullary cells, 78% cleaved to the compacted embryo stage and 69% cavitated as compared with 50 and 33% respectively for controls (P less than 0.01). Only 30% of co-cultured embryos reached the expanded blastocyst and 26% underwent hatching as compared with 28% for both stages in controls. At the 2 - 4- and 6 - 8-cell stages, 91 and 87% of co-cultured embryos showed an absence or slight fragmentation as compared with 72 and 61% respectively for embryos grown in medium alone (P less than 0.01). None of the co-cultured embryos showed unequal-sized blastomeres while 22% of controls showed unequal cleavage. Embryos grown with ampullary cells cleaved slightly faster than controls. Scanning electron micrographs showed that ampullary cells collected from co-cultures were all of the secretory type with several microvilli and apical protrusions. It is clear that subcultured human ampullary cells support human embryonic cleavage and yield a reasonable number of good quality embryos up to the cavitation stage. Development past the expanded blastocyst and hatching stages seems to involve another critical phase with its own specific requirements.
TL;DR: An adaptive cosine transform coding scheme for color images which incorporates human visual properties into the coding scheme is described and results show that the subjective quality of the reconstructed images at a bit rate of 0.4 bit/pixel or a compression ratio of 60:1 is very good.
Abstract: An adaptive cosine transform coding scheme for color images which incorporates human visual properties into the coding scheme is described. It employs adaptive quantization to exploit the statistical nature of the coefficients and adaptive block distortion equalization to reduce the block edge structures inherent in block transform coding schemes. Results show that the subjective quality of the reconstructed images at a bit rate of 0.4 bit/pixel or a compression ratio of 60:1 is very good. >
TL;DR: In this article, a survey of the variations of the coefficient of friction in dry sliding of steel on steel over a wide range of sliding conditions is presented in the form of a friction-regime map.
TL;DR: The data show that the responsive-ness of a cell to external stimuli can be reprogrammed by the expression of a single transcription factor and that differential expression of hormone receptors is at least one mechanism by which steroid-specific gene activation is achieved.
Abstract: ALTHOUGH glucocorticoids and progestins control vastly different physiological processes, the receptors mediating the effects of these hormones interact with the same DNA sequences1–4. Transfer experiments involving synthetic genes5 and in vitro binding studies6 have shown that progesterone and glucocorticoid receptors both recognize the same 15-base pair DNA element (TGTACAGGATGTTCT), raising the question of how the two steroids affect gene expression selectively. We considered the possibility that their selectivity arises from either the differential expression of the receptors in target cells or the differential dependence of receptor function on additional transcription factors. To test these alternatives we introduced a progesterone-receptor expression pi asm id into the rat hepatoma cell line Fto2B-3 which contains glucocorticoid receptor but is devoid of progesterone receptor. We report that expression of the progesterone receptor in Fto2B-3 cells renders endogenous glucocorticoid-regulated genes inducible by progestins. Our data show that the responsive-ness of a cell to external stimuli can be reprogrammed by the expression of a single transcription factor and that differential expression of hormone receptors is at least one mechanism by which steroid-specific gene activation is achieved.
Patent•
24 Apr 1989TL;DR: In this paper, a device for detecting chemical species in liquids having one or more sensor elements is described, each sensor element includes a test electrode coated with a perfluorinated ion exchange polymer film incorporating a redox mediator; an immobilized enzyme layer and, over this, a semipermeable membrane.
Abstract: A device for detecting chemical species in liquids having one or more sensor elements is described. Each sensor element includes a test electrode coated with a perfluorinated ion-exchange polymer film incorporating a redox mediator; an immobilized enzyme layer and, over this, a semipermeable membrane. The invention discloses the method whereby the test electrode is normally kept at a zero potential and then poised at a positive potential for a few milliseconds during which time the test signal is evaluated. The invention formulates a method for calibrating each measurement sample and reference solution wells. These are symetrically arranged with respect to the sensor element so that the center of the sample solution well and the center of the reference solution well are equidistant to the sensor element. Thus the diffusion of chemical species from the sample and reference solutions occurs equally and can be correlated. The invention additionally discloses a method for selectively detecting a number of species in a single sample drop through the provision of multi-sensor elements. The technique proposed in the invention is particularly suitable for the determination of glucose and cholesterol in biological fluids.
TL;DR: The authors investigated the association between work values and organizational commitment in the Asian context and found that intrinsic work values relate more closely to organizational commitment than either the global measure of work values or extrinsic work values.
Abstract: This paper seeks to investigate the association between work values and organizational commitment in the Asian context. Two major dimensions of work values, that is, intrinsic and extrinsic, were derived from a factor analysis of Wollack et al.'s scale. Organizational commitment was defined in terms of an individual's degree of identification and involvement in the work organization. This variable was measured using Porter et al.'s scale. The analysis suggested that intrinsic work values relate more closely to organizational commitment than either the global measure of work values or extrinsic work values.
TL;DR: A tissue culture system for obtaining high frequency shoot regeneration of Brassica campestris ssp.
TL;DR: There was clear monotonic dose-response association between PD and blood mercury levels and scalp hair mercury was shown to be a poor predictor of PD risk.
Abstract: A case-control study was conducted among the multiethnic population of Singapore to test the hypothesis that a high level of body burden mercury is associated with an increased risk of Parkinson''s di
TL;DR: It is concluded that no clear-cut displacement occurred in mixed experimental populations of Ae.
Abstract: Interactions among the larvae of Aedes aegypti (L.), Ae. albopictus (Skuse), and Ae. triseriatus (Say) were studied in trispecific and bispecific mixed populations under laboratory and field conditions. Competitive stress (as evidenced by the average time to first, 50, and 75% pupation and the total pupation periods for mixed populations of each species in comparison with their single species controls) was more pronounced in mixed cultures reared in glass jars in the laboratory than in tires under field conditions. In the laboratory, the larval development of Ae. aegypti reared together with Ae. albopictus or Ae. triseriatus, or both, larvae was accelerated significantly. Conversely, the time to pupation for Ae. albopictus and Ae. triseriatus was delayed when reared with Ae. aegypti. However, the average wing length of female Ae. albopictus and Ae. triseriatus was greater in the mixed cultures than in single species cultures. These data indicated that the effect of intraspecific competition was greater than interspecific competition. Adequate food and higher temperature appeared to promote rapid development and higher survival of the immature stages of the three Aedes species in tires placed in the field. In general, Ae. triseriatus larvae required a longer period for larval development and had greater larval mortality than either Ae. aegypti or Ae. albopictus. In mixed populations of Ae, albopictus and Ae. aegypti in the jars and food-rich tires, the periods needed to attain first, 50, and 75% cumulative pupation were not significantly different than in single species controls. We conclude that no clear-cut displacement occurred in mixed experimental populations of Ae. aegypti and Ae. albopictus.
TL;DR: Criteria on the swim-up semen should be used in the selection of patients admitted to IVF programs, and they justify the necessity of research investigations to improve motility in those patients with sluggish motility.
Abstract: Several sperm motility parameters in semen prepared by the swim-up technique were compared with IVF rates in 84 patients. The patients were either on clomiphene + human menopausal gonadotrophin or follicle stimulating hormone + human menopausal gonadotrophin stimulation regimens. Motility ratings were assessed both manually according to World Health Organization guidelines as well as computer-automated semen analysis (Cellsoft, Cryoresources, USA). Motility ratings of greater than or equal to 2 yielded significantly higher fertilization rates (78-82%) than ratings below 2 (20-23%) (p less than 0.001) for patients on both regimens. Velocity (41, 55, 78 microns/sec) and mean amplitude of lateral head displacement (1.96, 3.29, 4.91 microns) correlated significantly with and between manual ratings of 1, 2, and 3, respectively (r = 0.83; p less than 0.01). No significant differences were observed in linearity and beat/cross frequency between the manual ratings, although beat/cross frequencies tended to reduce linearly with increases in intensity of motility. The velocity of sperm motility has a significant effect on fertilization rates, and cut-off points of greater than or equal to 2 or greater than or equal to 50 microns/sec predict the actual potential and likely success of in vitro fertilization. These criteria on the swim-up semen should be used in the selection of patients admitted to IVF programs, and they justify the necessity of research investigations to improve motility in those patients with sluggish motility.
TL;DR: In this article, the authors proposed a scheme to cancel third-harmonic currents along a common neutral conductor by means of a six-phase system supplied by two transformers connected in antiphase.
Abstract: Causes for excessive neutral currents amounting to 75% and 157% of phase current values in two installations supplying predominantly fluorescent lighting circuits have been identified. These high neutral currents are accounted for by three main components, namely fundamental phase current unbalance, third-harmonic currents caused by saturation of ballasts, and more third-harmonic current caused by third-harmonic voltage waveform distortion in the supply. Solutions are presented to overcome the problem, including a scheme that cancels third-harmonic currents along a common neutral conductor by means of a six-phase system supplied by two transformers connected in antiphase. >
TL;DR: In this article, a three-dimensional cubic spline polynomial interpolation is used to find the optimal horizontal and vertical highway alignments simultaneously while subject to a wide range of possible constraints.
Abstract: This paper presents the formulation of a three-dimensional highway alignment optimization model. The coordinates of the highway is parametrized by using a three-dimensional cubic spline polynomial interpolation. The solution is obtained by locating the optimal horizontal and vertical alignments simultaneously while subject to a wide range of possible constraints. These constraints may be bounds on the slope or curvature, as well as avoidance of inaccessible region. It is an extension from a previous research work where optimal vertical highway alignment was determined for a preselected horizontal alignment. Two numerical examples based upon the actual ground conditions in Singapore are presented to illustrate the applicability of the proposed model. Some computational details such as scaling and selection of initial variables which affect the rate of convergence are also briefly discussed.
TL;DR: The long control region of the human papillomavirus type 16 genome is 856 base pairs (bp) long and contains a cell-type-specific enhancer, a glucocorticoid response element, and sequences mediating the response to the viral gene products of open reading frame E2; all three regulate the promoter P97.
Abstract: The long control region of the human papillomavirus type 16 genome is 856 base pairs (bp) long. It contains a cell-type-specific enhancer, a glucocorticoid response element, and sequences mediating the response to the viral gene products of open reading frame E2; all three regulate the promoter P97. We mapped binding sites of trans-acting proteins relevant for the cell-type-specific enhancer and other cis-acting elements by DNase I footprint experiments with nuclear extracts from HeLa cells. Throughout the human papillomavirus type 16 long control region 23 footprints protect 557 of 900 bp. Nine footprints fall into a 400-bp segment that was previously identified to contain the cell-type-specific enhancer. Variations of the protein concentration in the footprint reaction do not affect six of these nine footprints. At high protein concentrations, three footprints fuse to a 106-bp protected region, suggesting that this segment specifically binds several proteins of lower affinity or abundance. Unexpectedly, extracts from human MCF7 and mouse 3T3 cells, in which the enhancer is inactive, give footprints identical to those obtained with HeLa extracts. Seven footprints contain the sequence 5'-TTGGC-3'. Footprint competition experiments suggest that factor NFI binds to these seven motifs. Competition with cloned oligonucleotides in transfections suggests that these elements contribute to the enhancer function. Subcloning identifies a 232-bp fragment between positions 7524 and 7755 as sufficient for full enhancer activity. Several of the six footprinted elements on this segment may cooperate functionally, since subclones of this region show decreased or no cell-type-specific enhancer function.
TL;DR: The results provide evidence for different signaling pathways mediating transcript abundance and poly(A) tail length and demonstrate an apparent obligatory role for serotonin in osmotically induced AVP and OT mRNA accumulation.
TL;DR: In this article, the dynamic component of the cutting force has so far received little attention as a possible parameter for tool wear and tool failure monitoring, and a correlation is found between the dynamic cutting force and flank wear.
Abstract: The dynamic component of the cutting force has so far received little attention as a possible parameter for tool wear and tool failure monitoring. Analysis of the frequency spectrum shows a distinct peak frequency which is consistent for a wide range of machining conditions and for different lathes. The peak frequency source has been identified as being due to the natural frequency of the vibrating tool holder rather than oscillations arising from the chip formation process. Good correlation is found between the dynamic cutting force and flank wear. The dynamic force falls rapidly before the entry into the tertiary zone as well as prior to the onset of catastrophic tool failure.
TL;DR: In this article, the effects of a deep inhalation (DI) on degree of obstruction at various stages of their treatment and after recovery over several days were assessed for level of obstruction.
Abstract: Asthmatic patients who came to hospital for treatment of severe attacks were assessed for level of obstruction and the effects of a deep inhalation (DI) on degree of obstruction at various stages of their treatment and after recovery over several days. The more severe the obstruction, the greater was the constrictor effect of a DI; as lung function improved with intensive treatment, including corticosteroids, the constrictor effect diminished. Thus, we believe the constrictor effects of a DI relate to the degree of inflammation in the obstructive process. These longitudinal data relating severity to the effects of a DI were nearly identical to previously published cross-sectional data in a group of patients with spontaneous asthma with widely different levels of lung function. It is possible that the response to a DI in a given asthmatic subject serves as a functional marker for the predominant mechanism for obstruction.
TL;DR: It is suggested that VP, locally synthesized in pituicytes, may have paracrine effects on VP receptors in the neural lobe, and the osmotic stimulation of a 2% (wt/vol) NaCl drinking diet resulted in a marked accumulation of VP RNA in the Neural lobe.
Abstract: The peptides vasopressin (VP) and oxytocin are derived from preprohormone precursers encoded by highly homologous linked genes that are expressed in discrete groups of hypothalamic neurons. The mature hormones are released into the peripheral circulation from the neural (posterior) lobe of the pituitary and have also been implicated in the regulation of anterior lobe. We have used Northern blotting and in situ hybridization to RNA in tissue sections to describe the presence, anatomical localization, and regulation of VP and oxytocin RNAs in the pituitary gland itself. We were unable to detect VP transcripts in the anterior and intermediate lobes of the pituitary. Rather we found low levels of VP RNA in the neural lobe. Furthermore, the osmotic stimulation of a 2% (wt/vol) NaCl drinking diet resulted in a marked accumulation of VP RNA in the neural lobe. We suggest that VP, locally synthesized in pituicytes, may have paracrine effects on VP receptors in the neural lobe.
TL;DR: In this paper, the reflection and transmission characteristics of regular and random waves from a horizontal thin plate which is fixed at a certain submergence below the water surface, have been investigated and the experimental results are compared with the theoretical solution obtained numerically by the finite-element method using the linear-wave diffraction theory.
TL;DR: It is shown that pure NFI from porcine liver protects virtually the same nucleotides as a factor present in crude HeLa nuclear extracts in the LCR of HPV-16, and NFI seems to be necessary but not sufficient for HPV enhancer activation.
Abstract: The long control region (LCR) of human papillomaviruses (HPV) encompasses 5-12% of the viral genome and contains an intricate network of cis responsive elements. In the LCR of seven unrelated HPV-types, namely HPV-1, 6, 8, 11, 16, 18 and 33, we have identified clusters of 4 to 7 5-TTGGC-3 motifs suggesting nuclear factor I (NFI) binding sites. We randomly selected 20 (out of a total of 38) of these motifs and showed that pure NFI from porcine liver protects virtually the same nucleotides as a factor present in crude HeLa nuclear extracts. The footprints obtained with HeLa extracts in the LCR of HPV-16 are eliminated in competition experiments by an oligonucleotide representing the palindromic adenovirus NFI binding site. Restriction fragments from the genome of HPV-11, 16 and 18, which contain this cluster of NFI binding sites associated with binding sites of unrelated transcription factors, function as transcriptional enhancers. In contrast, a fragment from HPV-8 exhibiting exclusively NFI binding sites, or polymerized NFI sites from HPV-16, are functionally inactive. NFI seems to be necessary but not sufficient for HPV enhancer activation.