Showing papers by "National University of Singapore published in 1983"

FIR filter design over a discrete powers-of-two coefficient space

Abstract: FIR digital filters with discrete coefficient values selected from the powers-of-two coefficient space are designed using the methods of integer programming. The frequency responses obtained are shown to be superior to those obtained by simply rounding the coefficients. Both the weighted minimax and the weighted least square error criteria are considered. Using a weighted least square error criterion, it is shown that it is possible to predict the improvement that can be expected when integer quadratic programming is used instead of simple coefficient rounding.

2 Environmental Influences on Gonadal Activity in Fish

Abstract: Publisher Summary This chapter discusses environmental factors both as proximate factors that trigger gonadal development and breeding activities in many fish species, and as zeitgebers, which entrain endogenous rhythm in other species. It has now become apparent that different phases of the reproductive cycle of a particular fish species may require different proximate factors or zeitgebers. The chapter considers environmental influences on gametogenesis, spawning, and gonadal regression. Because the environmental requirements for reproduction are likely to differ among temperate, subtropical, and tropical species, these three groups of fish are considered separately wherever appropriate. To illustrate that knowledge gained concerning environmental influences on fish reproduction can be put to practical use, applications (both potential and actual) in aquaculture for broodstock management and induction of spawning are discussed in the chapter.

Clinical Science Stress Analysis of the Human Tooth Using a Three-dimensional Finite Element Model

Abstract: A three-dimensional finite element model has been developed for the purpose of analyzing the stress distribution in a human mandibular right first molar. The model takes into account the non-symmetric geometry and loading, and the material inhomogeneities of the tooth. Comparisons with existing two-dimensional analyses are given.

HLA and nasopharyngeal carcinoma in Chinese--a further study.

Abstract: This paper reports the results of 8 years of HLA typing of newly diagnosed nasopharyngeal carcinoma (NPC) patients among Chinese in Singapore, and compares the HLA profile of NPC cases with that of the normal Chinese population. Earlier results had indicated an association with A2 and BW46, but the heterogeneity of the earlier case series, which contained a proportion of long-term survivors, obscured other aspects of the relationship. In this paper, the risk associated with A2 (relative risk = 1.5) and BW46 (relative risk = 1.9) is confirmed, showing a much higher relative risk in the presence of both antigens, and a risk is also demonstrated for B17 (relative risk = 2.1). Relative risks of less than unity are observed for AII (relative risk = 0.5) and B13 (relative risk = 0.5). Data from family studies indicate the importance of the haplotype A2.BW46 in determining risk for NPC.

Origin of the rubrospinal tract in neonatal, developing, and mature rats

Abstract: This investigation describes the origin of the rubrospinal tract in neonatal (1-10 days old), developing (15-20 days old), and mature (2-4 months old) rats studied by using the horseradish peroxidase (HRP) method of tracing neuronal connections. HRP was administered in the cervical or lumbosacral segments of the spinal cord either in the crystal or solution form. The results showed that the rubrospinal tract extended to the lumbosacral part of the spinal cord at birth. There appeared to be no difference in the pattern of labelled rubrospinal (RS) neurons following the administration of HRP in the cervical or the lumbosacral cord segment of the neonatal, developing, and mature rats. In rats of these three age groups, labelled neurons were found bilaterally in the red nucleus, with a contralateral predominance, and they were found in both the parvicellular and magnocellular portions of the red nucleus. There was a somatotopic arrangement in the labelled RS neurons: Those projecting to the cervical cord segments were located in the dorsal and dorsomedial regions of the red nucleus and those projecting to the lumbosacral cord segments were located in the ventral and ventrolateral regions of the nucleus.

Reception of PSK Signals Over Fading Channels Via Quadrature Amplitude Estimation

Abstract: We consider here a new approach to PSK signal detection over a slow nonselective Rayleigh fading channel which does not require a carrier recovery loop. The receiver achieves coherent demodulation by making use of estimates of the quadrature amplitudes of the received PSK signals in its likelihood ratio test. The receiver is assumed to have a memory containing information on the past received signals which enables it to generate the estimates. The error rate of the receiver can be evaluated analytically and computer simulation results are presented to verify the predicted performance.

Boundary value problems for higher order integro- differential equations

Abstract: where R(t) = (x(t), x’(t), . . . , X@ -‘J(t)) and A is a continuous operator map: C(“-l)[al, a,] + C[ar, a,]. The function f is continuous in all of its arguments. The problem (l.l), (1.2) includes several particular cases, for example the boundary value problems for the differential equations if A = 0, considered in [7,8] and the references therein, for the integro-differential equations of the Volterra type if

Epstein-Barr virus specific T-cell response in nasopharyngeal carcinoma patients.

Abstract: There is a substantial body of evidence suggesting an association between Epstein-Barr virus (EBV) and undifferentiated nasopharyngeal carcinoma (NPC). The present study has compared a group of NPC patients (newly diagnosed and long-term survivors) and controls for EBV-specific T-cell immunity using the regression of transformation assay. Newly diagnosed patients (17 tested) when compared with either long-term survivors (20 tested) or controls (30 tested) showed a significant impairment in virus-specific T-cell immunity (p = 0.036, p = 0.043 respectively). Furthermore, donors with IgA antibody to EBV showed a significant depression in virus-specific T-cell immunity compared with donors without IgA antibody (19 IgA-positive, 48 IgA-negative; p = 0.0025). These results may be important in explaining the postulated role of EBV in the aetiology of NPC.

Cholinoreceptors in the corpus cavernosum muscle of the human penis.

Abstract: 1 Acetylcholine produced contraction, relaxation or a biphasic effect on corpus cavernosum muscle strips of human penis. These effects were antagonized by atropine but were modified by hexamethonium or tetrodotoxin suggesting the presence of excitatory and inhibitory muscarinic receptors in the human penis. 2 Nicotine and DMPP also produced contraction or relaxation of the corpus cavernosum muscle strips. These effects were presumably indirect as they were abolished by hexamethonium and tetrodotoxin. 3 Contractions produced by nicotine or DMPP were abolished by atropine whereas the relaxations produced by these agents were only partially blocked by atropine. Hence, the receptors mediating these relaxations are unlikely to be entirely muscarinic.

Uptake and distribution of mercury in mice from ingesting soluble and insoluble mercury compounds.

Abstract: The toxicity of mercury to animals and man depends greatly on the form of the compound. In general, organic mercury compounds are more poisonous than inorganic mercury. There have been many reports on the mercury uptake and distribution in different animal organs with soluble organic mercury. But so far, very little work has been done by gavage on less soluble inorganic mercuric sulfide which is widely used in the Chinese medicine. The paper presented to compares short term and long term uptake and tissue distribution of mercury in mice from ingesting pure and crude mercuric sulfide to a more soluble mercuric chloride.

Role‐playing as an experimental strategy in social psychology

Abstract: It is argued that the efficacy of role playing as an experimental strategy should be assessed in terms of its ability to resolve the problems of experimentation in social psychology. Via an epistemological and methodological analysis of the laboratory experiment in social psychology, it is argued that ‘active-experimental’ role playing constitutes a promising experimental strategy, because it can potentially overcome the fundamental experimental problem that arise in virtue of the relational nature of social psychological phenomena. It is stressed that in the end the question of the efficacy of role playing as an experimental strategy is an empirical one, but also that most empirical evaluations are inadequate for two reasons. Most of the role playing groups lack realism and involvement, and the congruence of results in role playing studies of deception experiments (whose validity is questionable) is uncritically taken as both the standard and the criterion for the efficacy of role playing. Both role playing and deception techniques should be assessed in terms of their capacity to achieve experimental realism.

Carbon fixation in orchid aerial roots

Abstract: SUMMARY Orchid aerial roots contained chlorophylls and were shown to be capable of photosynthesis. 14C0 2 feeding in the light showed that the C 3 pathway was operating during the day. Aerial roots also exhibited diurnal acidity fluctuations typical of crassulacean acid metabolism (CAM) and malate was the only labelled compound isolated after night 14C0 2 feeding. C0 2 exchange patterns in aerial roots were consistent with CAM C02 fixation during the night hours. The rate of photosynthetic C02 fixation in the light was much greater than the rate of CAM C02 fixation in the night. Measurements of C02 exchange, however, showed little or no net uptake indicating that these roots were not completely autotrophic.

The Effects of Alternative Methods of Accounting for Leases – An Experimental Study

Abstract: A report of an experiment testing analysts' reactions to alternative ways of reporting lease commitments. Results indicate that reporting methods affect the behaviour of financial analysts in projecting earnings, but not in share valuations.

Optimal Financial and Foreign-Exchange Liberalization of Less Developed Economies

Abstract: This paper models a typical highly inflationary less developed economy, in which monetary forces are the result of three policy determinants: the rate of monetary expansion (µ), the interest rate on bank deposits (d), and the rate of depreciation of the real exchange rate (A…). The task confronting policy-makers is to reduce the equilibrium inflation rate without undue transitional sacrifice of the growth objective. We demonstrate that this optimally requires the precise coordination of all three instruments, with high but declining values of d and µ being adopted initially, and with A… being modulated so as to forestall excessive capital inflows and to influence favorably the evolution of relative input prices.

Effect of IgA deposits on the glomerular mesangium in Berger's disease.

Abstract: In mesangial IgA glomerulonephritis (Berger's disease), the immunoproteins appeared to gain access from the capillary lumen to the mesangium via endothelial fenestrae or via channels between the endothelial cells. The deposits are transported into the deeper mesangium by a process of imbibition or diffusion, with the matrix acting as the bed. There are no true channels or grooves in the mesangial matrix for the transport of the immunoproteins. The contractility of the glomerular myoid fibrils may account for the movement of deposits to the hilus for possible removal. There was partial dissolution of the deposits in the mesangial matrix accompanied by loosening of the matrix. No evidence was found for any significant intracellular phagocytosis and digestion. The mesangial deposits directly or indirectly stimulated the cellular hypertrophy and hyperplasia and increased deposition of mesangial matrix. This was accompanied by formation of collagen fibrils within the thickened matrix and led to atrophy of the ...

A method of studying the effect of adhesives on denture retention.

Abstract: lhe physical forces that hold a denture in situ include those acting on the fitting surfaces of the denture base and the supporting mucosal surface. Different authors have reviewed the influence of adhesive and cohesive forces, surface tension, atmospheric pressure, the viscosity and volume of saliva, and gravity on denture retention.‘” Clinical procedures during impression making are designed to obtain a maximum area of coverage, an intimate tissue/denture contact, and an effective border seal. There are occasional situations in which it is not possible to obtain the desirable optimal retention. In these instances patients frequently resort to the use of denture adhesives. The objective of this article is an evaluation of the effect on retention of two such adhesives under controlled conditions in vivo by means of a hydraulic sensor.

Efficient special purpose linear programming for FIR filter design

Abstract: A high efficiency special purpose linear programming algorithm for FIR filter design is introduced, This algorithm incorporates FFT and FIR zero-phase filters to assist in the computation. Compared to the general purpose linear programming, this special purpose linear programming produces large savings in the computing cost when used to design FIR filters. The savings increase with the length of the filter being designed.

Autopilot for ship control. part 1. theoretical design

Abstract: A self-tuning ship-autopilot design is presented that reconciles the conflicting demands of course keeping and of manoeuvring by using two modes of operation. During the course-keeping mode the performance criterion is formulated to minimise heading error, propulsion losses and rudder activity, while in the manoeuvring phase the concern is simply to minimise heading error. The system parameters are identified using recursive least-squares estimation to confer on the autopilot a high degree of adaptability, as illustrated in the simulation studies of part 2 of the paper.