Dengue Virus Surveillance for Early Warning, Singapore

In Singapore, after a major outbreak of dengue in 2005, another outbreak occurred in 2007. Laboratory-based surveillance detected a switch from dengue virus serotype 1 (DENV-1) to DENV-2. Phylogenetic analysis showed a clade replacement within DENV-2 cosmopolitan genotype, which accompanied the predominant serotype switch, and cocirculation of multiple genotypes of DENV-3

Entomologic and molecular investigation into Plasmodium vivax transmission in Singapore, 2009

<p>Abstract</p> <p>Background</p> <p>Singapore has been certified malaria free since November 1982 by the World Health Organization and despite occasional local transmission, the country has maintained the standing. In 2009, three clusters of malaria cases were reported in Singapore.</p> <p>Methods</p> <p>Epidemiological, entomological and molecular studies were carried out to investigate the three clusters, namely Mandai-Sungei Kadut, Jurong Island and Sembawang.</p> <p>Results</p> <p>A total of 29 malaria patients, with no recent travel history, were reported in the three clusters. Molecular analysis based on the <it>msp3α </it>and <it>msp1 </it>genes showed two independent local transmissions: one in Mandai-Sungei Kadut and another in Sembawang. Almost all cases within each cluster were epidemiologically linked. In Jurong Island cluster, epidemiological link remains uncertain, as almost all cases had a unique genetic profile. Only two cases shared a common profile and were found to be linked to the Mandai-Sungei Kadut cluster. Entomological investigation found <it>Anopheles sinensis </it>to be the predominant Anopheline in the two areas where local transmission of <it>P. vivax </it>was confirmed. <it>Anopheles sinensis </it>was found to be attracted to human bait and bites as early as 19:45 hrs. However, all <it>Anopheles </it>mosquitoes caught were negative for sporozoites and oocysts by dissection.</p> <p>Conclusion</p> <p>Investigation of <it>P. vivax </it>cases from the three cluster areas confirmed the occurrence of local transmission in two areas. Although <it>An. sinensis </it>was the predominant Anopheline found in areas with confirmed transmission, the vector/s responsible for the outbreaks still remains cryptic.</p

Entomologic and Virologic Investigation of Chikungunya, Singapore

Data from longitudinal analyses can be useful in the design and implementation of control strategies

International Consensus Statement on Rhinology and Allergy: Rhinosinusitis

Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR‐RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR‐RS‐2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence‐based findings of the document. Methods: ICAR‐RS presents over 180 topics in the forms of evidence‐based reviews with recommendations (EBRRs), evidence‐based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICAR‐RS‐2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence‐based management algorithm is provided. Conclusion: This ICAR‐RS‐2021 executive summary provides a compilation of the evidence‐based recommendations for medical and surgical treatment of the most common forms of RS

Five-Level Multiple-Pole PWM AC-AC Converters with Reduced Components Count

This paper proposes novel multilevel AC/DC/AC converters with reduced number of semiconductor devices to achieve light weight, efficiency and better input current quality. The proposed three-phase front-end bidirectional five-level (5L) rectifier and rear-end 5L-inverter are constructed based on multiple-pole multilevel diode-clamped approach (M2DCC), which consist a total number of 24 diode components clamped. Based on M2DCC concept, the number of switching devices can be further reduced to construct a new unidirectional front-end rectifier (M2SCR). Comparative studies are conducted to analyze the performances of the two proposed front-end rectifiers with supportive mathematical derivations. Experimental prototypes have proven the feasibility of the proposed AC/DC/AC configurations. Results obtained show that low current harmonic distortions of 5% and high power factor of 0.99 are achieved with small input inductors despite of low switching frequency operation at 1 kHz.Accepted versio

NPC photovoltaic grid-connected inverter using proportional-resonant controller

Multi-megawatt photovoltaic (PV) power plants are widespread in electrical power systems because of the drastic decrease in the PV panel prices. The multi-string structure is considered for high power PV systems due to the increase in the overall energy conversion efficiency and the modularity when compared to the centralized topology. High power conversion can be achieved easily using parallel connection of several grid-tied two-level voltage-source inverters (2L-VSIs). However, this configuration complicates the control designs. Thus, this issue can be overcome by replacing these 2L-VSIs with a single high power three-level neutral point clamped inverter (3L-NPC). Moreover, the 3L-NPC inherits several attractive merits such as improved power quality with reduced total harmonic distortion (THD), increased overall efficiency as well as lower costs. In addition to that, the voltage oriented control using proportional-resonant (VOC-PR) in conjunction with the adaptive space vector modulation (ASVM) technique is proposed for the large-scaled PV system with grid-tied NPC inverter. The feasibility of the proposed control for the high power system is validated through the simulation results under various environmental conditions. Besides that, the dynamic mance of the system under the proposed VOC-PR is greatly enhanced in comparison with the conventional method using PI controller.ASTAR (Agency for Sci., Tech. and Research, S’pore)Accepted versio

A review of active/reactive power control strategies for PV power plants under unbalanced grid faults

Fault ride through (FRT) capability is one of the challenges faced in the medium to high voltage large-scale grid-tied photovoltaic power plants (PVPPs). Besides that, due to the high penetration of installed distributed generation (DG) units, the grid voltage enhancement under unbalanced faults is a requirement of several standards and grid codes. The controller of the grid-connected inverter consists mainly of two parts: the selection of the reference active/reactive power and the calculation of the reference currents under faults. This paper reviews various strategies which are proposed in the reported literature for calculating the reference current as well as selecting the reference active/reactive power based on the grid voltage. The performances of these control strategies are investigated on the 150 kW NPC grid-connected multi-string PVPP, which is considered as the state of the art for medium power PVPPs. The PVPP is connected to the 12.47 kV medium voltage distribution system where different fault situations is simulated.ASTAR (Agency for Sci., Tech. and Research, S’pore)Accepted versio