Showing papers by "University of Malaya published in 1976"
TL;DR: In this article, an imporved theoretical model to predict the thermal performance of a natural-recirculation (thermosiphon-flow) solar water heater system is presented.
102 citations
73 citations
TL;DR: A mechanism of competitive occupation of vacant synaptic sites was proposed to explain the sprouting phenomenon and no anomalous fibres could be traced to the trigeminal complex and the rostral reticular formation in the medulla.
Abstract: Following neonatal lesion in the sensorimotor and adjacent cortex (SMC) in the albino rats, a corresponding region in the contralateral intact cortex gave rise to a bilateral corticofugal projection to the pretectal area, superior colliculus, pons, gracile and cuneate nuclei, the nucleus of Bischoff, caudal medullary reticular formation and the spinal cord. The anomalous growth response was greatest when the initial lesion was made within the first three days after birth, but became much reduced as the initial lesion was made at a progressively older age. A significant amount of anomalous projection could, however, still be demonstrated in the pons even in animals first lesioned as late as 20 days postnatal. The sprouting phenomenon was precise and ordered and in the various regions studied, the pattern of anomalous projection mirrored that of the normal projection. The anomalous fibres reached their specific target cells either by deflecting ipsilaterally at the pyramidal decussation to reach the spinal cord and the caudal medulla or by running across the mid-line to the contralateral pons, superior colliculus, pretectal area and the thalamic ventrobasal complex. In contradistinction to the findings of Hicks and D'Amato (1975) no anomalous fibres could be traced to the trigeminal complex and the rostral reticular formation in the medulla. A mechanism of competitive occupation of vacant synaptic sites was proposed to explain the sprouting phenomenon.
56 citations
TL;DR: In this article, a planar model for cholesteric liquid crystals is proposed, in which the intermolecular potential is required to contain chiral contributions as a result of symmetry considerations.
Abstract: As a first step toward constructing a general molecular model for cholesteric liquid crystals, we propose here a planar model in which the intermolecular potential is required to contain chiral contributions as a result of symmetry considerations. By means of a mean-field analysis, we identify the microscopic basis for the existence of the cholesteric phase. The latter is shown to be a consequence of chirality. The temperature dependence of the cholesteric pitch is discussed, and several numerical examples are given. Our theoretical deductions are consistent with experimental observations. We indicate, however, that under exceptional circumstances two unobserved phenomena may be found to exist. First, particular systems made up of chiral molecules may exist in the nematic phase. Next, as temperature is varied, a particular pure cholesteric substance may undergo untwisting and reverse its helicity after passing through a divergence in pitch.
51 citations
TL;DR: The amino acid composition profiles for the six varieties of cassava varied and the total amino acids ranged from 8.42 to 9.4% while the essential amino acids averaged 4.21% and the sulphur-containing amino acids only 0.25%.
49 citations
TL;DR: A survey was made of the relationship between ground covers, soil fertility, and the growth of Hevea brasiliensis in Malaysia, finding that legumes initially had the fastest rate of growth, and generally contained more nutrients than the other covers tested.
Abstract: A survey was made of the relationship between ground covers, soil fertility, and the growth of Hevea brasiliensis. Four different cover management systems were widely tested in Malaysia, namely a mixture of creeping legumes (Calopogonium muconoides, Centrosema pubescens and Pueraria phaseoloides), grasses (mostly Axonopus compressus with Paspalum conjugatum), a pure crop of Mikania cordata, and a naturally regenerating system representing the normal colonisation process on cleared land. Of the four systems, legumes initially had the fastest rate of growth, and generally contained more nutrients than the other covers tested. The greater nutrient return to the soil from growing a leguminous cover was reflected in higher levels of these nutrients in rubber leaves. This, coupled with improved soil physical properties, led to an increased rate of growth of the rubber tree. Nitrogen fixation under legumes grown in association with rubber averaged 150 kg per ha per year over a 5-year period, with maximum rates of nitrogen fixation being about 200 kg per ha per year. Competition effects from both the shade and roots of Hevea caused a gradual diminution in vigour of all the covers such that they virtually died out by about the 6th year after planting. Dry rubber yield benefits in ex-leguminous plots extended for about 20 years, and amounted to approximately 4 metric tonnes more than the yields achieved with any of the other cover systems. In simple economic terms this means that only 4% of the monetary benefit of a legume cover policy derives from nitrogen fixation while the remaining 96% stems from post-legume effects. Two hypotheses have been invoked to explain these effects: first, that legumes re-cycle nutrients at or near the soil surface until such a stage that they can be efficiently utilised by Hevea; and second, that legumes, by processes not fully understood, cause increased Hevea root proliferation which facilitates nutrient uptake.
49 citations
TL;DR: Acylated anthocyanins were found to be abundant in the Melastomataceae but were not found in closely allied families, supporting the separation of the Lecythidaceae from the Myrtiflorae.
45 citations
TL;DR: The present study confirms the suggestive evidence brought forth by the finding of Leong and Lund that following neonatal lesion of the sensorimotor and adjacent cortex of the albino rats, the remaining intact contralateral cortex projects bilaterally to the superior colliculus, pons and spinal cord.
45 citations
44 citations
TL;DR: In this article, the authors used linear regression analysis to measure the amount of potassium, strontium, and rubidium in volcanic rocks of the Indonesian active volcanic arc, extending from Sumatra through Java, Sumbawa, and Flores to Sulawesi, Sangihe, and Halmahera, have been related to depth of the underlying Benioff zone by multiple linear regression analyses.
Abstract: The amounts of potassium, strontium, and rubidium in volcanic rocks of the Indonesian active volcanic arc, extending from Sumatra through Java, Sumbawa, and Flores to Sulawesi, Sangihe, and Halmahera, have been related to depth of the underlying Benioff zone by multiple linear regression analysis. The following equations for the arc from Sumatra to Sumbawa have correlation coefficients better than 0.80 (level of significance Depth to the Benioff zone (km) = 397 - (5.26 x % of SiO 2 ) + (35.04 x % of K 2 O) = 373 - (4.36 x % of SiO 2 ) + ( 0.73 x ppm of Rb) = 110 - (0.03 x % of SiO 2 ) + ( 0.14 x ppm of Sr). The standard error of depth estimate is about 30 km. The correlation coefficient for the first equation is slightly better than for the other two.
35 citations
TL;DR: In this paper, the authors studied a deep profile on gneiss from Malaysia and found that the alteration of biotite to halloysite takes place within a few centimeters of the fresh rock (at 18.5 m depth).
TL;DR: In this paper, a two-stage model of the propagation of 1-50 MeV solar-flare cosmic rays is presented, where the first stage consists of a thin spherical shell of radius near the Sun, which feeds particles into interplanetary space (the second stage) where they propagate along the Archimedean mean inter-planetary magnetic field under the influences of anisotropic diffusion, convection, and energy changes.
Abstract: A two-stage model of the propagation of 1–50 MeV solar-flare cosmic rays is presented. The first stage consists of a thin spherical shell of radius ra near the Sun which feeds particles into interplanetary space (the second stage) where they propagate along the Archimedean mean interplanetary magnetic field under the influences of anisotropic diffusion, convection, and energy changes. To calculate the time dependence at a fixed point in space, account is taken of the corotation of flux tubes past the observer.
TL;DR: In 14 Malesian species of Hibiscus (sensu lato) the most common floral anthocyanin was cyanidin 3-sambubioside, and cyanid in 3-glucoside was found.
TL;DR: The authors characterizes doubly stochastic operators between two L 1 spaces of random variables in terms of convex functions on the real line, which is then applied to proving some Hardy-Littlewood-Polya-type rearrangement theorems.
TL;DR: Two children manifested EEG discharges which were triggered by blinking and/or eye closure in light and in darkness and it is suggested that sensory afferents arising from contraction of the orbicularis oculi muscles may have been the epileptic trigger in Case 1 and could have contributed to the epilepsy triggering mechanism in Case 2.
TL;DR: In this article, the IR and NMR spectra of cationic complexes of the variety (Me 3 SnL) + X − {L = oPo, diphosO 2, oAso, BipyO 2 ; X = ClO 4, PF 6, Ph 4 B, PF 6 } have been reported.
TL;DR: In this paper, a scheme was proposed to explain the formation of lactone groups from the reaction products of the rubber epoxide and simple amino-acids, and the presence of other functional groups was discussed.
TL;DR: In this article, the modified Benesi-Hildebrand equation was applied to the hydrogen bonding between chloroform and tetrahydrofuran in cyclohexane medium.
TL;DR: The "rapid" attenuation of cross reactivity among different plant leghaemoglobins is explicable in terms of the extensive amino acid substitutions which have been demonstrated in the literature and in the present studies.
Abstract: Circular dichroism studies on leghaemoglobins from snake bean, lupin, serradella and other plants show that, in common with soybean (reported earlier) they have a similar overall polypeptide chain conformation and haem environment and orientation. Immunochemical studies, on the other hand, suggest that the antigenic determinants on the surface of the leghaemoglobins vary considerably.
Thus, firstly the α-helix content of the leghaemoglobins as a class is very similar (60–65%) and approaches that of the myoglobins, secondly, the sign, magnitude and shape of their circular dichroism spectra in the near ultraviolet, Soret and visible regions suggest close similarities in the environment and orientation of a structurally important tryptophan residue and of the haem moiety, and thirdly, there is comparatively weak haem-protein interaction.
The extent of immuno cross-reactivity was found to be best demonstrated using the Farr radioimmunoassay procedure. The results were (a) 5 leghaemoglobins from one plant (soybean) crossreacted completely but with varying affinities. (b) The extent of cross reactivity between leghaemoglobins from different plants was compared to that within a single plant; the reaction of antiserum to a soybean leghaemoglobin with a serradella leghaemoglobin was weak, with a snake bean leghaemoglobin still weaker (and incomplete) while lupin leghaemoglobins showed no cross reactivity at all. (c) The “rapid” attenuation of cross reactivity among different plant leghaemoglobins is explicable in terms of the extensive amino acid substitutions which have been demonstrated in the literature and in the present studies. (d) In view of this rapid divergence it is not surprising that sperm whale and horse heart myoglobins showed no cross reactivity with soybean leghaemoglobins.
In summary, amino acid substitutions in the leghaemoglobin family are conformationally but not immunochemically conservative.
TL;DR: The rat muscle homogenate was found to contain deaminase capable of converting adenosine to inosine which was retained by the anionic-exchange resin at pH values above 7.5 in the presence of EDTA, which would lead to an erroneous estimation of phosphodiesterase activity.
TL;DR: A kinetic study of the aqueous persulphate initiated polymerisation of methacrylamide has shown that the rate of polymerisation is represented by the equation R p = k [M ] [I ] 1 2 where the overall rate constant, k = 1.3 × 10 9 exp (−18,400/ RT ) 1 1 2 mol − 1 2 s −1. Chain transfer with monomer, where CM = 5.4 × 10−3 at 60°, is the dominant transfer step.
TL;DR: In this paper, a modified version of the original procedure was used to obtain naked protoplasts which reduced acetylene after a lag period of about 2 d, and continue to do so for at least 11 d.
Abstract: NITROGEN-FIXING protoplasts are of obvious importance in physiological studies of the assimilation of atmospheric nitrogen; in investigations of nodule development; in cloning trials for experimental and agricultural purposes1; and in somatic cell hybridisation2–5. Production of such protoplasts has proved elusive, however. Davey et al.6 introduced a technique for the isolation of protoplasts from nodules. Protoplasts prepared by their procedure were incapable of nitrogenase (EC 1.7.99.2)-dependent acetylene reduction7, presumably as a result of the extensive loss of leghaemoglobin during the isolation process7. By modifying the original procedure6, we have obtained naked protoplasts which reduce acetylene after a lag period of about 2 d, and continue to do so for at least 11 d.
TL;DR: Tapioca (Manihot esculenta, kekabu variety) leaf rhodanese was purified 7.8 fold by column chromatography on Sephadex G-10, acetone fractionation a.
TL;DR: The distinctive features in the ultrastructure of S. booliati were the thinness of the cyst wall, the absence of cytophaneres or trabeculae and the comparatively small number of micronemes in the zoites.
TL;DR: A reversible gel with microtubular structure was found distending the superficial vessels of the ulcer biopsy, as well as extravascularly, and the protein studied here is similar to a reported instance of myeloma cryo-IgGk.
Abstract: Recurrent gangrenous leg ulcers were associated with a monoclonal IgGk cryoglobulinaemia, though without overt myeloma. Cryoprecipitation of the serum in vitro gave a reversible gel with microtubular structure, built from the monomer and with a high degree of order. The same structure was found distending the superficial vessels of the ulcer biopsy, as well as extravascularly. There was no vasculitis, and luminal obstruction appeared responsible for the ulceration. Microtubular structures occur in nature among diverse proteins and viruses. The protein studied here is similar to a reported instance of myeloma cryo-IgGk.
TL;DR: Of the 25 malignant neoplasms, hepatocellular carcinoma was by far the commonest (36%) and nine patients with this neoplasm had coexistant macronodular cirrhosis; the nine cases occurring in the Senoi appear to have a high predilection for liver cancer.
Abstract: Necropsies were performed on 285 consecutively unclaimed Orang Asli bodies from Gombak Orang Asli Hospital during an eight-year period from May 1967 to April 1975. Of the 25 malignant neoplasms, hepatocellular carcinoma was by far the commonest (36%). The nine patients with this neoplasm had coexistant macronodular cirrhosis. There were 20 cases of cirrhosis; 45% of these had coexistant hepatocellular carcinoma. The 53,000 Orang Aslis living in West Malaysia comprise three tribes, the Negrito, Senoi, and Melayu Asli (Proto Malays). The Sinoi appear to have a high predilection for liver cancer, all our nine cases occurring in this group. These aboriginal people live in the jungles where they practice shifting cultivation and maintain their own dietary and social customs. Detailed studies of their dietary habits may provide a clue to the etiology of liver cancer in these people.