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Campus Mobility for the Future: The Electric Bicycle  [PDF]
I. V. McLoughlin, I. K. Narendra, L. H. Koh, Q. H. Nguyen, B. Seshadri, W. Zeng, C. Yao
Journal of Transportation Technologies (JTTs) , 2012, DOI: 10.4236/jtts.2012.21001
Abstract: Sustainable and practical personal mobility solutions for campus environments have traditionally revolved around the use of bicycles, or provision of pedestrian facilities. However many campus environments also experience traffic congestion, parking difficulties and pollution from fossil-fuelled vehicles. It appears that pedal power alone has not been sufficient to supplant the use of petrol and diesel vehicles to date, and therefore it is opportune to investigate both the reasons behind the continual use of environmentally unfriendly transport, and consider potential solutions. This paper presents the results from a year-long study into electric bicycle effectiveness for a large tropical campus, identifying barriers to bicycle use that can be overcome through the availability of public use electric bicycles.
Percutaneous coronary intervention in asians- are there differences in clinical outcome?
Angela S Koh, Lay W Khin, Lok M Choi, Ling L Sim, Terrance S Chua, Tian H Koh, Jack W Tan, Stanley Chia
BMC Cardiovascular Disorders , 2011, DOI: 10.1186/1471-2261-11-22
Abstract: A prospective registry of consecutive patients undergoing PCI from January 2002 to December 2007 at a tertiary care center was analyzed. Primary endpoint was major adverse cardiovascular events (MACE) of myocardial infarction (MI), repeat revascularization and all-cause death at six months.7889 patients underwent PCI; 7544 (96%) patients completed follow-up and were included in the analysis (79% males with mean age of 59 years ± 11). There were 5130 (68%) Chinese, 1056 (14%) Malays and 1001 (13.3%) Indian patients. The remaining 357 (4.7%) patients from other minority ethnic groups were excluded from the analysis. The primary end-point occurred in 684 (9.1%) patients at six months. Indians had the highest rates of six month MACE compared to Chinese and Malays (Indians 12% vs. Chinese 8.2% vs. Malays 10.7%; OR 1.55 95%CI 1.24-1.93, p < 0.001). This was contributed by increased rates of MI (Indians 1.9% vs. Chinese 0.9% vs. Malays 1.3%; OR 4.49 95%CI 1.91-10.56 p = 0.001), repeat revascularization (Indians 6.5% vs. Chinese 4.1% vs. Malays 5.1%; OR 1.64 95%CI 1.22-2.21 p = 0.0012) and death (Indians 11.4% vs. Chinese 7.6% vs. Malays 9.9%; OR 1.65 95%CI 1.23-2.20 p = 0.001) amongst Indian patients.These data indicate that ethnic variations in clinical outcome exist following PCI. In particular, Indian patients have higher six month event rates compared to Chinese and Malays. Future studies are warranted to elucidate the underlying mechanisms behind these variations.The widespread utilization of PCI as a treatment strategy for coronary artery disease has altered the management of patients with CAD [1,2]. Several reports have examined the outcomes following PCI of various patient populations [3-9]. While population registries a decade ago have shown differences in coronary mortality following an acute myocardial infarction (MI) among various ethnic groups, contemporary reports of differences in clinical outcomes following PCI among Asians remain limited [10-13].The object
Efficiencies of Aloof-Scattered Electron Beam Excitation of Metal and Graphene Plasmons
Kelvin J. A. Ooi,Wee Shing Koh,Hong Son Chu,Dawn T. H. Tan,L. K. Ang
Physics , 2015, DOI: 10.1109/TPS.2014.2379259
Abstract: We assessed the efficiencies of surface plasmon excitation by an aloof-scattered electron beam on metals and graphene. Graphene is shown to exhibit high energy transfer efficiencies at very low electron kinetic energy requirements. We show that the exceptional performance of graphene is due to its unique plasmon dispersion, low electronic density and thin-film structure. The potential applications of these aloof-scattered graphene plasmons are discussed in aspects of coherent radiation.
A direct extension of Meller's calculus
E. L. Koh
International Journal of Mathematics and Mathematical Sciences , 1982, DOI: 10.1155/s0161171282000726
Abstract: This paper extends the operational calculus of Meller for the operator B ±=t ¢ ’ ±ddtt ±+1ddt to the case where ± ¢ (0, ¢ ). The development is la Mikusinski calculus and uses Meller's convolution process with a fractional derivative operator.
Cosmological Perturbations in Non-Commutative Inflation
Koh, Seoktae;Brandenberger, Robert H.
High Energy Physics - Phenomenology , 2007, DOI: 10.1088/1475-7516/2007/06/021
Abstract: We compute the spectrum of cosmological perturbations in a scenario in which inflation is driven by radiation in a non-commutative space-time. In this scenario, the non-commutativity of space and time leads to a modified dispersion relation for radiation with two branches, which allows for inflation. The initial conditions for the cosmological fluctuations are thermal. This is to be contrasted with the situation in models of inflation in which the accelerated expansion of space is driven by the potential energy of a scalar field, and in which the fluctuations are of quantum vacuum type. We find that, in the limit that the expansion of space is almost exponential, the spectrum of fluctuations is scale-invariant with a slight red tilt. The magnitude of the tilt is different from what is obtained in a usual inflationary model with the same expansion rate during the period of inflation. The amplitude also differs, and can easily be adjusted to agree with observations.
Evolution of Gravitational Perturbations in Non-Commutative Inflation
Koh, Seoktae;Brandenberger, Robert H.
High Energy Physics - Phenomenology , 2007, DOI: 10.1088/1475-7516/2007/11/013
Abstract: We consider the non-commutative inflation model of [3] in which it is the unconventional dispersion relation for regular radiation which drives the accelerated expansion of space. In this model, we study the evolution of linear cosmological perturbations through the transition between the phase of accelerated expansion and the regular radiation-dominated phase of Standard Cosmology, the transition which is analogous to the reheating period in scalar field-driven models of inflation. If matter consists of only a single non-commutative radiation fluid, then the curvature perturbations are constant on super-Hubble scales. On the other hand, if we include additional matter fields which oscillate during the transition period, e.g. scalar moduli fields, then there can be parametric amplification of the amplitude of the curvature perturbations. We demonstrate this explicitly by numerically solving the full system of perturbation equations in the case where matter consists of both the non-commutative radiation field and a light scalar field which undergoes oscillations. Our model is an example where the parametric resonance of the curvature fluctuations is driven by the oscillations not of the inflaton field, but of the entropy mode
Cosmic Microwave Background Radiation anisotropy with primordial magnetic fields
Seoktae Koh,Chul H. Lee
Physics , 2000, DOI: 10.1103/PhysRevD.62.083509
Abstract: Galactic magnetic fields are observed of order $\sim 10^{-6}G$, but their origin is not definitely known yet. In this paper we consider the primordial magnetic fields generated in the early universe and analyse their effects on the density perturbations and the CMBR anisotropy. We assume that the random magnetic fields have the power law spectrum and satisfy the force-free field condition. The peak heights of the CMBR anisotropy are shown to be shifted upward depending on the magnetic field strengths relative to the no-magnetic field case.
Cosmic Background Anisotropy due to Neutrino Oscillations Revisited
Seoktae Koh,Chul H. Lee
Physics , 2001,
Abstract: This paper has been withdrawn by the author due to a crucial error in several equations.
Local Inflammation Induces Complement Crosstalk Which Amplifies the Antimicrobial Response
Jing Zhang,Jingyun Koh,Jinhua Lu,Steffen Thiel,Benjamin S. H. Leong,Sunil Sethi,Cynthia Y. X. He,Bow Ho equal contributor,Jeak L. Ding equal contributor
PLOS Pathogens , 2009, DOI: 10.1371/journal.ppat.1000282
Abstract: By eliciting inflammatory responses, the human immunosurveillance system notably combats invading pathogens, during which acute phase proteins (CRP and cytokines) are elevated markedly. However, the Pseudomonas aeruginosa is a persistent opportunistic pathogen prevalent at the site of local inflammation, and its acquisition of multiple antibiotic-resistance factors poses grave challenges to patient healthcare management. Using blood samples from infected patients, we demonstrate that P. aeruginosa is effectively killed in the plasma under defined local infection-inflammation condition, where slight acidosis and reduced calcium levels (pH 6.5, 2 mM calcium) typically prevail. We showed that this powerful antimicrobial activity is provoked by crosstalk between two plasma proteins; CRP:L-ficolin interaction led to communication between the complement classical and lectin pathways from which two amplification events emerged. Assays for C4 deposition, phagocytosis, and protein competition consistently proved the functional significance of the amplification pathways in boosting complement-mediated antimicrobial activity. The infection-inflammation condition induced a 100-fold increase in CRP:L-ficolin interaction in a pH- and calcium-sensitive manner. We conclude that the infection-induced local inflammatory conditions trigger a strong interaction between CRP:L-ficolin, eliciting complement-amplification pathways which are autonomous and which co-exist with and reinforce the classical and lectin pathways. Our findings provide new insights into the host immune response to P. aeruginosa infection under pathological conditions and the potential development of new therapeutic strategies against bacterial infection.
Prevalence of invasive fungal disease in hematological patients at a tertiary university hospital in Singapore
Siok-Ying Lee, Chay-Leng Yeo, Winnie H Lee, Andrea L Kwa, Liang-Piu Koh, Li-Yang Hsu
BMC Research Notes , 2011, DOI: 10.1186/1756-0500-4-42
Abstract: We conducted a retrospective chart review of all hematological patients who developed possible, probable or definite IFD according to EORTC/MSG criteria in the period from Oct 2007 to Apr 2010. The prevalence of IFD was determined via correlation with institutional database records of all hematological patients treated at our institution over the same time period.There were 39 cases of IFD diagnosed during the study period, with 8 (20.5%) possible, 19 (48.7%) probable and 12 (30.8%) definite cases of IFD. Aspergillus spp. accounted for 83.9% of all probable and definite infections. There was 1 case each of Rhinocladelia spp., Coprinopsis cinerea, Exserohilum spp. sinusitis and Rhizopus spp. sinusitis. IFD occurred in 12 of 124 (9.7%) AML and 4 of 103 (3.9%) ALL patients treated at our institution respectively. There were 10 (16.1%) infections among 62 allogeneic HSCT recipients, six of whom were having concurrent graft-versus-host disease (GVHD). Five other cases occurred after allogeneic HSCT failure, following salvage chemotherapy for disease relapse. The prevalence of IFD during induction chemotherapy was 8.9% (11 of 124 cases) for AML and 1.0% (1 of 103 cases) for ALL. Fluconazole prophylaxis had been provided for 28 out of the 39 (71.8%) cases, while 4 (10.3%) were on itraconazole prophylaxis. The in-hospital mortality was 28.2% (11 of 39 cases), of which 5 (12.8%) deaths were attributed to IFD.The burden of IFD is high in our institution, especially in allogeneic HSCT recipients and patients on induction chemotherapy for AML. A prophylactic strategy directed against invasive mould infections for local high-risk patients may be considered as the comparative costs of treatment, prolonged hospitalisation and subsequent delayed chemotherapy favours such an approach.Antifungal prophylaxis is recommended for patients undergoing induction chemotherapy for acute myeloid leukemia (AML) and patients with allogeneic hematopoietic stem cell transplantation (HSCT) undergoi
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