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A decade of fertility below replacement level in Singapore

Saw SH

J Biosoc Sci, 1986 Oct;18(4):395-401.
PMID: 3782191
Ethnic fertility differentials in Peninsular Malaysia and Singapore

Saw SH

J Biosoc Sci, 1990 Jan;22(1):101-12.
PMID: 2298755

Differences in fertility between the three major ethnic groups (Malays, Chinese and Indians) in Peninsular Malaysia and Singapore have existed since before the onset of fertility decline in the late 1950s and remain today, although the relative positions and the actual differences have changed due to the varying rates of decline. By 1987, the Malays experienced the highest fertility and the Chinese the lowest in both countries but in Singapore the Malay fertility was lower than the Chinese fertility in Peninsular Malaysia. The fertility differentials will lead to changes in the ethnic composition in both countries but more so in Peninsular Malaysia.
Fertility differentials in early postwar Malaya

Saw SH

Demography, 1967 Jun;4(2):641-56.
PMID: 21318676 DOI: 10.2307/2060305

During the early postwar years up to 1957, the three main races in Malaya - Malays, Chinese, and Indians - experienced some differences in their levels of fertility. The lowest fertility was recorded among the Malays, with Chinese and Indian fertility about 5 percent and 10 percent higher, respectively. The comparatively low fertility of the Malays was owing to the exceptionally high rate of divorce, which meant unstable marriages and shorter periods of exposure to the risk of childbearing.A fairly well-defined pattern of state differences in fertility levels is found to exist in Malaya. Briefly, fertility was on the high side in the northern states of Johore, Malacca, and Negri Sembilan, and on the low side in the northern states of Penanq, Kelantan, Perlis, Kedah, and Trengganu, with the central states of Perak, Selangor, and Pahang in the intermediate position.The usual rural-urban fertility differentials are seen to prevail in Malaya as a whole and in the smaller units at state levels. Finally, the three main races registered higher fertility in rural areas, and the greatest gap between rural and urban rates prevailed among the Chinese.
Errors in chinese age statistics

Saw SH

Demography, 1967 Jun;4(2):859-75.
PMID: 21318696 DOI: 10.2307/2060325

The first section of this paper is devoted to an analysis of some theoretical aspects of the Chinese system of reckoning ages, and the second section offers a method of collecting the age statistics of a Chinese population: A discussion of the errors found in the age returns and the unsuccessful measures taken to eradicate these errors in the Malayan censuses conducted prior to1957 leads to an appraisal of the method of collecting Chinese age data in the 1957 census.
Fulltext Results of plasma radiative compression investigation in the PF-24 device operated with D2, Ar and (100%-x)D2+x%Ar mixtures obtained using the 5-phase Lee model code

Marciniak Ł, Akel M, Kulińska A, Lee S, Scholz M, Saw SH

Appl Radiat Isot, 2022 Jan 21;182:110118.
PMID: 35091151 DOI: 10.1016/j.apradiso.2022.110118

The article presents new results for plasma radiative compression in high-current discharges in the z-pinch configuration. The results are based on the 113 discharges performed in the plasma-focus PF-24 device operated with D2, Ar and (100%-x)D2+xAr mixtures, with Ar pressure fractions x ≈ 3-60% (mole fractions). The constant initial total pressure is about 2.9 mbar and the constant initial pressure of Ar is 1.2 mbar. Each experimental discharge was simulated individually using the 5-phase Lee model code to carry out the fitting procedure of the total discharge current waveform. The results from these 113 computed discharges fitted to the corresponding 113 experimental discharges show that the increase of the effective atomic number of the gas mixture increases the probability of occurrence of plasma radiative compression phenomenon. Relatively weak radiative compression was found for part of the discharges in 15-60% range of Ar mole fractions and in Ar, while the stronger radiative compression occurred for part of discharges in Ar only. This is because there was too little total x-ray line radiation emission during the equilibrium pinch lifetime related to the very small amount of swept up mass and the low current flow through pinched plasma, represented by the decreasing values of model parameters as the Ar mole fraction increases. The results show that the main pinch parameters influencing the occurrence and strength of radiative compression are: total x-ray line emission yield, effective atomic number, initial pinch radius, initial pinch ion number density and initial pinch ion/electron temperature.
In situ determination of the static inductance and resistance of a plasma focus capacitor bank

Saw SH, Lee S, Roy F, Chong PL, Vengadeswaran V, Sidik AS, et al.

Rev Sci Instrum, 2010 May;81(5):053505.
PMID: 20515137 DOI: 10.1063/1.3429207

The static (unloaded) electrical parameters of a capacitor bank are of utmost importance for the purpose of modeling the system as a whole when the capacitor bank is discharged into its dynamic electromagnetic load. Using a physical short circuit across the electromagnetic load is usually technically difficult and is unnecessary. The discharge can be operated at the highest pressure permissible in order to minimize current sheet motion, thus simulating zero dynamic load, to enable bank parameters, static inductance L(0), and resistance r(0) to be obtained using lightly damped sinusoid equations given the bank capacitance C(0). However, for a plasma focus, even at the highest permissible pressure it is found that there is significant residual motion, so that the assumption of a zero dynamic load introduces unacceptable errors into the determination of the circuit parameters. To overcome this problem, the Lee model code is used to fit the computed current trace to the measured current waveform. Hence the dynamics is incorporated into the solution and the capacitor bank parameters are computed using the Lee model code, and more accurate static bank parameters are obtained.
Fulltext Chromosomal rearrangements and protein globularity changes in Mycobacterium tuberculosis isolates from cerebrospinal fluid

Saw SH, Tan JL, Chan XY, Chan KG, Ngeow YF

PeerJ, 2016;4:e2484.
PMID: 27688977 DOI: 10.7717/peerj.2484

BACKGROUND: Meningitis is a major cause of mortality in tuberculosis (TB). It is not clear what factors promote central nervous system invasion and pathology but it has been reported that certain strains of Mycobacterium tuberculosis (Mtb) might have genetic traits associated with neurotropism.
METHODS: In this study, we generated whole genome sequences of eight clinical strains of Mtb that were isolated from the cerebrospinal fluid (CSF) of patients presenting with tuberculous meningitis (TBM) in Malaysia, and compared them to the genomes of H37Rv and other respiratory Mtb genomes either downloaded from public databases or extracted from local sputum isolates. We aimed to find genomic features that might be distinctly different between CSF-derived and respiratory Mtb.
RESULTS: Genome-wide comparisons revealed rearrangements (translocations, inversions, insertions and deletions) and non-synonymous SNPs in our CSF-derived strains that were not observed in the respiratory Mtb genomes used for comparison. These rearranged segments were rich in genes for PE (proline-glutamate)/PPE (proline-proline-glutamate), transcriptional and membrane proteins. Similarly, most of the ns SNPs common in CSF strains were noted in genes encoding PE/PPE proteins. Protein globularity differences were observed among mycobacteria from CSF and respiratory sources and in proteins previously reported to be associated with TB meningitis. Transcription factors and other transcription regulators featured prominently in these proteins. Homologs of proteins associated with Streptococcus pneumoniae meningitis and Neisseria meningitidis virulence were identified in neuropathogenic as well as respiratory mycobacterial spp. examined in this study.
DISCUSSION: The occurrence of in silico genetic differences in CSF-derived but not respiratory Mtb suggests their possible involvement in the pathogenesis of TBM. However, overall findings in this comparative analysis support the postulation that TB meningeal infection is more likely to be related to the expression of multiple virulence factors on interaction with host defences than to CNS tropism associated with specific genetic traits.
Mutations in atpG2 may confer resistance to gentamicin in Listeria monocytogenes

Ng JML, Ngeow YF, Saw SH, Ng HF, Zin T

J Med Microbiol, 2022 Dec;71(12).
PMID: 36748567 DOI: 10.1099/jmm.0.001618

Introduction Listeriosis, a foodborne infection caused by Listeria monocytogenes, could lead to febrile listerial gastroenteritis and a more invasive form which is often associated with a high mortality and hospitalisation rate. Gentamicin, used as an adjunct therapy with ampicillin, remains the treatment of choice for this life-threatening and invasive infection.Gap statement Nevertheless, there is little data on gentamicin resistance determinants in L. monocytogenes.Aim In this study, we selected and characterised B2b, a gentamicin-resistant mutant derived from L. monocytogenes ATCC 19115 to determine the target(s) of resistance in L. monocytogenes after exposure to gentamicin.Methodology Whole-genome sequencing was carried out to identify the mutation site(s) and possible mechanism(s) of resistance. The mutant was characterised using antimicrobial susceptibility testing and PCR. For biological verifications, complementation and allelic exchange mutagenesis were carried out.Results We found that the gentamicin resistance in B2b was caused by a 10 bp deletion in atpG2 which encodes a gamma subunit of the ATP synthase in L. monocytogenes. Using atpG2 PCR, various other mutations were identified in other gentamicin resistant mutants derived from ATCC 19115. In addition, the mutation from B2b, when introduced into L. ivanovii, also caused gentamicin resistance in this Listeria species.Conclusion Hence, atpG2 mutations appear to be important determinants of gentamicin resistance not only in L. monocytogenes but possibly also in other Listeria species.