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Search Results: 1 - 10 of 5872 matches for " Tin-Yam Chan "
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Exploration of the Deep-Sea Fauna of Papua New Guinea
Eric Pante,Laure Corbari,Justine Thubaut,Tin-Yam Chan
Oceanography , 2012,
Abstract: Little is known of New Guinea's deep benthic communities. In fall 2010, the Muséum national d'Histoire naturelle, Institut de Recherche pour le Développement, and University of Papua New Guinea spearheaded an international three-leg cruise, BioPapua, aimed at exploring the deep waters of eastern Papua New Guinea and its satellite islands. Special attention was given to faunal assemblages associated with sunken wood and decomposing vegetation as well as seamount summits and slopes. In this article, we review the information available on the deep ecosystems of Papua New Guinea and summarize preliminary results of the BioPapua cruise.
Evolutionary Divergence of Geographic Subspecies within the Scalloped Spiny Lobster Panulirus homarus (Linnaeus 1758)
Shane D. Lavery, Ahmad Farhadi, Hamid Farahmand, Tin-Yam Chan, Ashkan Azhdehakoshpour, Vibhavari Thakur, Andrew G. Jeffs
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0097247
Abstract: Panulirus homarus is an economically important spiny lobster that is widespread through the Indo-West Pacific Region, but has an uncertain taxonomic status, with three or four geographic subspecies having been described. This study used mitochondrial (16S, COI and control region) and nuclear (18S, ITS-1) DNA sequences to examine specimens of all putative subspecies and forms from throughout their range, in order to determine their genetic validity, and understand the evolutionary history of this species. Despite the range of diversity present in the loci examined, the results were consistent across genes. P. h. rubellus from the SW Indian Ocean comprised the most divergent lineage that was reciprocally monophyletic with respect to all other P. homarus (approx. 9% divergence in COI), and has likely evolved reproductive barriers. The putative P. h. “Brown” subspecies from the Marquesas Is in the central Pacific also comprised a somewhat divergent monophyletic lineage (approx. 3% in COI), but may simply be an allopatric population. The widespread P. h. homarus was not diverged at all from the described P. h. megasculpta from the NW Indian Ocean. The degree of evolutionary divergence of populations at the extremes distribution of the species is somewhat surprising, given the long pelagic larval stage, but suggests that allopatric speciation has been an important driver in the evolution of the genus.
Influence of electron scatterings on thermoelectric effect
Jing Li,Tin Cheung Au Yeung,Chan Hin Kam
Physics , 2012, DOI: 10.1063/1.4740235
Abstract: In this work, we employed non-equilibrium Green's function to investigate the electron transport properties in the nanowire with the presence of scatterings. The scattering mechanism is modelled by using the concept of B\"uttiker probe. The effect of electron scattering is analyzed under three conditions: absence of external field; with a bias voltage; and with a finite temperature difference. It is found weak and strong scatterings strength affect the electron transport in different ways. In the case of weak scattering strength, electron trapping increase the electron density, hereafter boost the conductance significantly. Although the increment in conductance would reduce the Seebeck coefficient slightly, the power factor still increases. In the case of strong scattering strength, electron diffraction causes the redistribution of electrons, accumulation of electron at the ends of the wire blocks current flow; hence the conductance is reduced significantly. Although the Seebeck coefficient increases slightly, the power factor still decreases. The power factor is enhanced by 6%-18%, at the optimum scattering strength.
Sidelobes Reduction Using Simple Two and Tri-Stages Non Linear Frequency Modulation (Nlfm)
Yee Kit Chan;Ming Yam Chua;Voon Chet Koo
PIER , 2009, DOI: 10.2528/PIER09073004
Abstract: The Linear Frequency Modulation (LFM) waveform is the most commonly and extensively used signal in practical radar system. However a compressed LFM signal at the receiver will produce the first sidelobe at a level of -13 dB to the peak of the main lobe. A weighting function is needed to apply in order to reduce the sidelobes. However, the penalty of mismatch loss is clearly evident. It may reduce output SNR, typically by 1 to 2 dB. Every single dB of additional SNR can have great effects in reducing false alarm rates in target detection applications. In an effort to achieve low autocorrelation sidelobe level without applying weighting function, Non-Linear Frequency Modulation (NLFM) signal has been investigated. This paper describes the sidelobe reduction techniques using simple two-stage FM waveform, modified two-stage FM waveform and tri-stage FM waveform. Simulation results of the proposed NLFM signal are presented. Sidelobe reduction of more than -19 dB can be achieved by this design without any weighting technique applied.
Oracle, Multiple Robust and Multipurpose Calibration in a Missing Response Problem
Kwun Chuen Gary Chan,Sheung Chi Phillip Yam
Statistics , 2014, DOI: 10.1214/13-STS461
Abstract: In the presence of a missing response, reweighting the complete case subsample by the inverse of nonmissing probability is both intuitive and easy to implement. When the population totals of some auxiliary variables are known and when the inclusion probabilities are known by design, survey statisticians have developed calibration methods for improving efficiencies of the inverse probability weighting estimators and the methods can be applied to missing data analysis. Model-based calibration has been proposed in the survey sampling literature, where multidimensional auxiliary variables are first summarized into a predictor function from a working regression model. Usually, one working model is being proposed for each parameter of interest and results in different sets of calibration weights for estimating different parameters. This paper considers calibration using multiple working regression models for estimating a single or multiple parameters. Contrary to a common belief that overfitting hurts efficiency, we present three rather unexpected results. First, when the missing probability is correctly specified and multiple working regression models for the conditional mean are posited, calibration enjoys an oracle property: the same semiparametric efficiency bound is attained as if the true outcome model is known in advance. Second, when the missing data mechanism is misspecified, calibration can still be a consistent estimator when any one of the outcome regression models is correctly specified. Third, a common set of calibration weights can be used to improve efficiency in estimating multiple parameters of interest and can simultaneously attain semiparametric efficiency bounds for all parameters of interest. We provide connections of a wide class of calibration estimators, constructed based on generalized empirical likelihood, to many existing estimators in biostatistics, econometrics and survey sampling and perform simulation studies to show that the finite sample properties of calibration estimators conform well with the theoretical results being studied.
A Longitudinal Analysis of the Stability of Household Money Demand  [PDF]
Jan Tin
Modern Economy (ME) , 2011, DOI: 10.4236/me.2011.23046
Abstract: Past aggregate time-series studies, conducted under the assumption of a representative economic agent, frequently show that the demand for narrowly defined M1, especially non-interest-yielding demand deposit, is unstable during periods of financial innovations. Whether this is longitudinally the case among life-cycle savers is unclear. This study utilizes longitudinal data to take another look and find that volatility in the demand for non-interest-earning checking accounts in the mid and late 1990s is attributable solely to the portion held for the transactions motive. When the conventional Baumol-Tobin model is extended to include human capital and family formation variables representing the life-cycle motive, equilibrium money demand is a stable function of both economic and demographic variables.
Agrobacterium-mediated transient transformation of Pentalinon andrieuxii Müll. Arg.  [PDF]
Alejandro Yam-Puc, Elidé Avilés-Berzunza, Manuel J. Chan-Bacab, Luis Manuel Pe?a-Rodríguez, Gregorio Godoy-Hernández
Advances in Bioscience and Biotechnology (ABB) , 2012, DOI: 10.4236/abb.2012.33035
Abstract: Sections of hypocotyls, roots and leaves from Pentalinon andrieuxii plantlets were transiently transformed with Agrobacterium tumefaciens LBA4404 bearing the binary plasmid pCAMBIA2301 with an interrupted β-Glucuronidase (GUS) gene. Histochemical GUS assays showed transient gene expression in all infected tissues, being older roots those which displayed the most intense GUS staining. To our knowledge, this is the first report of Pentalinon andrieuxii susceptibility to Agrobacterium tumefaciens-mediated genetic transformation.
Long-term care cost drivers and expenditure projection to 2036 in Hong Kong
Roger Y Chung, Keith YK Tin, Benjamin J Cowling, King Chan, Wai Chan, Su Lo, Gabriel M Leung
BMC Health Services Research , 2009, DOI: 10.1186/1472-6963-9-172
Abstract: We parameterised a macro actuarial simulation with data from official demographic projections, Thematic Household Survey 2004, Hong Kong's Domestic Health Accounts and other routine data from relevant government departments, Hospital Authority and other LTC service providers. Base case results were tested against a wide range of sensitivity assumptions.Total projected LTC expenditure as a proportion of GDP reflected secular trends in the elderly dependency ratio, showing a shallow dip between 2004 and 2011, but thereafter yielding a monotonic rise to reach 3.0% by 2036. Demographic changes would have a larger impact than changes in unit costs on overall spending. Different sensitivity scenarios resulted in a wide range of spending estimates from 2.2% to 4.9% of GDP. The availability of informal care and the setting of formal care as well as associated unit costs were important drivers of expenditure.The "demographic window" between the present and 2011 is critical in developing policies to cope with the anticipated burgeoning LTC burden, in concert with the related issues of health care financing and retirement planning.Among developed economies, there have been progressively vocal concerns expressed about how to fund long-term care (LTC) for their ageing populations, given generally low fertility rates which are only partly compensated for by immigration [1-5]. This problem is particularly acute in Hong Kong because its fertility rate is the lowest on a sustained basis [6] and its life expectancy is one of the longest in the world [7]. People aged 65 or over will increase by 176% in the next 30 years to 2036, while individuals aged 80 or over will rise even more rapidly by 277% within the same period [8]. This is inevitable for Hong Kong as large birth cohorts of baby boomers plus those born to the large migration waves of young workers during the 1950s and 1960s reach old age over the period [9]. The gravity of the potential burden becomes immediately apparent fro
Kocuria kristinae infection associated with acute cholecystitis
Edmond SK Ma, Chris LP Wong, Kristi TW Lai, Edmond CH Chan, WC Yam, Angus CW Chan
BMC Infectious Diseases , 2005, DOI: 10.1186/1471-2334-5-60
Abstract: We describe the first case of K. kristinae infection associated with acute cholecystitis. The microorganism was isolated from the bile of a 56-year old Chinese man who underwent laparoscopic cholecystectomy. He developed post-operative fever that resolved readily after levofloxacin treatment.Our report of K. kristinae infection associated with acute cholecystitis expands the clinical spectrum of infections caused by this group of bacteria. With increasing number of recent reports describing the association between Kocuria spp. and infectious diseases, the significance of their isolation from clinical specimens cannot be underestimated. A complete picture of infections related to Kocuria spp. will have to await the documentation of more clinical cases.Kocuria is a member of the Micrococcaceae family and consists of nine species. It was previously classified into the genus of Micrococcus, but was dissected from Micrococcus based on phylogenetic and chemotaxonomic analysis [1]. The organism is widespread in nature and is frequently found as normal skin flora in humans and other mammals. Documented cases of infections due to Kocuria spp. are limited. The type species K. rosea has been reported to cause catheter-related bacteremia [2]. Another member of the genus, K. kristinae (previously known as Micrococcus kristinae), was first described in 1974 [3]. This organism is an aerobic, gram-positive coccus occurring in tetrads, and the majority of strains are non-pathogenic. Clinically similar to K. rosea, a single case of catheter-related bacteremia due to K. kristinae has been reported in a patient with ovarian cancer [4]. Here we report the first case of K. kristinae isolated from bile in a patient with acute cholecystitis.A 56-year old Chinese man, who had a known history of asymptomatic gallstones, presented with right upper quadrant abdominal pain for five days associated with fever. Laboratory investigations showed neutrophilia, but the liver function test was normal.
Total Variation Regularization of Matrix-Valued Images
Oddvar Christiansen,Tin-Man Lee,Johan Lie,Usha Sinha,Tony F. Chan
International Journal of Biomedical Imaging , 2007, DOI: 10.1155/2007/27432
Abstract: We generalize the total variation restoration model, introduced by Rudin, Osher, and Fatemi in 1992, to matrix-valued data, in particular, to diffusion tensor images (DTIs). Our model is a natural extension of the color total variation model proposed by Blomgren and Chan in 1998. We treat the diffusion matrix D implicitly as the product D=LLT, and work with the elements of L as variables, instead of working directly on the elements of D. This ensures positive definiteness of the tensor during the regularization flow, which is essential when regularizing DTI. We perform numerical experiments on both synthetical data and 3D human brain DTI, and measure the quantitative behavior of the proposed model.
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