A Non-Electrolytic-Capacitor Low-Power AC-DC Single-Stage SEPIC-Flyback LED Converter

This paper presents an isolated single-stage SEPIC-flyback ac-dc converter for supplying light emitting diode (LED) that can eliminate electrolytic capacitor adoption. The Single Ended Primary Inductor Converter (SEPIC) converter performs the power factor correction (PFC) function, while the flyback converter regulates the DC stage and provides circuit isolation for LED protection. This paper analyses the operation of the proposed LED topology and verifies the performance of the circuit using PSCAD simulation. The converter achieved a high power factor, low total harmonic distortion and low output voltage ripple. The proposed circuit also obtained voltage below 450 V across the storage capacitor, allowing low voltage rating components employment

A Comprehensive Review on Recent Developments of LED Drivers

Background: In these recent years, LED lighting has been widely implemented for household and industrial applications. By implementing the correct topology, the performance of a LED driver can be improved in terms of efficiency, power factor, lifespan, size and cost of development. Objective: This paper aims to provide a comprehensive review on the latest trends of LED driver design to serve as a useful guide for design engineers and researchers. Result: Latest research journals and conference proceedings have been reviewed. Conclusion: There are suitable converter topologies for LED drivers of varied power levels, with the flyback converter being the most suitable for applications of less than 100W. When designing the LED driver, considerations must be made on the power factor, efficiency, dimming capability, and lifespan

Perioperative analgesic modality and effectiveness in paediatric patients who have undergone common major urology surgery - a two-year retrospective study

Perioperative paediatric major urology surgery pain management remains challenging. These surgeries require general anaesthesia (GA) combined with either regional analgesia technique or systemic morphine infusion for optimal pain relief. We aimed to compare and evaluate the effectiveness of both analgesic techniques. This single centre retrospective descriptive study involved 88 patients, aged 3 months to 12 years old with American Society of Anaesthesiologists (ASA) I or II status, who underwent major urology surgery under GA. Group A patients received perioperative systemic morphine while Group B received regional anaesthesia blocks (continuous caudal epidural infusion, single-shot caudal blocks or single-shot erector spinae blocks). We measured requirements of perioperative rescue intravenous (IV) fentanyl, pain scores using Face, Leg, Activity, Cry, Consolability (FLACC) scale, perioperative non-opioid IV analgesia usage and associated complications. Intraoperative rescue fentanyl in both groups was comparable. Intraoperative non-opioid analgesia and postoperative rescue fentanyl requirement were significantly higher in Group A compared to Group B (p<0.001). Median FLACC scores in Group A were higher than Group B (p<0.001) for first 12 hours post-surgery. Commonest complications in Group A was vomiting (38.6%) and peri-catheter leak in Group B (6.81%). Regional anaesthesia technique is superior to systemic morphine in providing analgesia in the first 12 hours post paediatric major urology surgery and is devoid of opioid side effects

An Apicoplast Localized Ubiquitylation System Is Required for the Import of Nuclear-encoded Plastid Proteins

Apicomplexan parasites are responsible for numerous important human diseases including toxoplasmosis, cryptosporidiosis, and most importantly malaria. There is a constant need for new antimalarials, and one of most keenly pursued drug targets is an ancient algal endosymbiont, the apicoplast. The apicoplast is essential for parasite survival, and several aspects of its metabolism and maintenance have been validated as targets of anti-parasitic drug treatment. Most apicoplast proteins are nuclear encoded and have to be imported into the organelle. Recently, a protein translocon typically required for endoplasmic reticulum associated protein degradation (ERAD) has been proposed to act in apicoplast protein import. Here, we show ubiquitylation to be a conserved and essential component of this process. We identify apicoplast localized ubiquitin activating, conjugating and ligating enzymes in Toxoplasma gondii and Plasmodium falciparum and observe biochemical activity by in vitro reconstitution. Using conditional gene ablation and complementation analysis we link this activity to apicoplast protein import and parasite survival. Our studies suggest ubiquitylation to be a mechanistic requirement of apicoplast protein import independent to the proteasomal degradation pathway.This work was funded by grants from the National Institutes of Health to BS (AI 64671) and funds provided by the University of California, Riverside to KLR. SA was supported by a predoctoral fellowship from the American Heart Association, and GGD by a C.J. Martin Overseas Fellowship from the Australian National Health and Medical Research Council. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Crystal structure of rhodopsin bound to arrestin by femtosecond X-ray laser.

G-protein-coupled receptors (GPCRs) signal primarily through G proteins or arrestins. Arrestin binding to GPCRs blocks G protein interaction and redirects signalling to numerous G-protein-independent pathways. Here we report the crystal structure of a constitutively active form of human rhodopsin bound to a pre-activated form of the mouse visual arrestin, determined by serial femtosecond X-ray laser crystallography. Together with extensive biochemical and mutagenesis data, the structure reveals an overall architecture of the rhodopsin-arrestin assembly in which rhodopsin uses distinct structural elements, including transmembrane helix 7 and helix 8, to recruit arrestin. Correspondingly, arrestin adopts the pre-activated conformation, with a ∼20° rotation between the amino and carboxy domains, which opens up a cleft in arrestin to accommodate a short helix formed by the second intracellular loop of rhodopsin. This structure provides a basis for understanding GPCR-mediated arrestin-biased signalling and demonstrates the power of X-ray lasers for advancing the frontiers of structural biology

A Homozygous Mutation in the Tight-Junction Protein JAM3 Causes Hemorrhagic Destruction of the Brain, Subependymal Calcification, and Congenital Cataracts

The tight junction, or zonula occludens, is a specialized cell-cell junction that regulates epithelial and endothelial permeability, and it is an essential component of the blood-brain barrier in the cerebrovascular endothelium. In addition to functioning as a diffusion barrier, tight junctions are also involved in signal transduction. In this study, we identified a homozygous mutation in the tight-junction protein gene JAM3 in a large consanguineous family from the United Arab Emirates. Some members of this family had a rare autosomal-recessive syndrome characterized by severe hemorrhagic destruction of the brain, subependymal calcification, and congenital cataracts. Their clinical presentation overlaps with some reported cases of pseudo-TORCH syndrome as well as with cases involving mutations in occludin, another component of the tight-junction complex. However, massive intracranial hemorrhage distinguishes these patients from others. Homozygosity mapping identified the disease locus in this family on chromosome 11q25 with a maximum multipoint LOD score of 6.15. Sequence analysis of genes in the candidate interval uncovered a mutation in the canonical splice-donor site of intron 5 of JAM3. RT-PCR analysis of a patient lymphoblast cell line confirmed abnormal splicing, leading to a frameshift mutation with early termination. JAM3 is known to be present in vascular endothelium, although its roles in cerebral vasculature have not been implicated. Our results suggest that JAM3 is essential for maintaining the integrity of the cerebrovascular endothelium as well as for normal lens development in humans