Single mode operation of impurity-induced disordering large area vertical cavity surface emitting lasers

Vertical-cavity surface-emitting lasers (VCSELs) with suitable interdiffusion quantum wells profile by the use of selective impurity-induced disordering is proposed for high power single mode operation in large area devices. It is shown that the transverse optical confinement in the quantum well active region formed by the diffusion profile counteracts the influence of carrier spatial hole burning for VCSELs biased at high injection current. Results indicate that a single mode operation can be maintained in VCSELs with the diameter of core region equal to 50µm.published_or_final_versio

Fabry Perot semiconductor lasers with periodic diffused quantum wells structure

Fabry Perot semiconductor laser with periodic change in the extent of interdiffusion along the longitudinal direction of the quantum well active region is proposed to improve the discrimination between cavity modes.published_or_final_versio

High-power single-mode operation in DFB and FP lasers using diffused quantum-well structure

Distributed feedback (DFB) and Fabry-Perot (FP) semiconductor lasers with step and periodic interdiffusion quantum-well structures are proposed for high-power single-longitudinal-mode operation. It is shown that the phase-adjustment region formed by the diffusion step (i.e., step change in optical gain and refractive index) counteracts the influence of spatial hole burning, especially for DFB lasers with large coupling-length products biased at high injection current. Furthermore, it is found that with careful design of the diffusion grating (i.e., grating period and amount of diffusion extent) of FP lasers, side-mode suppression ratio can be enhanced and threshold current density can be minimized to a satisfied level.published_or_final_versio

Review of contraceptive use among women seeking for repeat termination of pregnancy in Hong Kong

Termination of pregnancy (TOP) is one of the commonly performed gynaecological procedures. We carried out this retrospective review to study the contraceptive practice among women seeking for first-time versus repeat TOPs. We analysed the data of 596 women attending the Family Planning Association of Hong Kong for TOP during January to March 2005. Among them, 340 (57.0%) of cases were seeking first-time TOP, 161 (27.0%) were undergoing second TOP, and 95 (15.9%) undergoing TOP for the third or more times. Overall, 43% of the cases under review were having repeat …postprin

Vertical-cavity surface-emitting semiconductor lasers with diffusedquantum wells

A self-consistent dynamic model is developed including the current distribution, carrier diffusion rate and spatial hole burning effects to investigate the modulation response of vertical-cavity surface-emitting lasers with diffused quantum wells structure. It is found that the overall performance including relaxation oscillation frequency and modulation bandwidth is improved.published_or_final_versio

Cost-Effective Use of Silver Dressings for the Treatment of Hard-to-Heal Chronic Venous Leg Ulcers

Aim To estimate the cost-effectiveness of silver dressings using a health economic model based on time-to-wound-healing in hard-to-heal chronic venous leg ulcers (VLUs). Background Chronic venous ulceration affects 1–3% of the adult population and typically has a protracted course of healing, resulting in considerable costs to the healthcare system. The pathogenesis of VLUs includes excessive and prolonged inflammation which is often related to critical colonisation and early infection. The use of silver dressings to control this bioburden and improve wound healing rates remains controversial. Methods A decision tree was constructed to evaluate the cost-effectiveness of treatment with silver compared with non-silver dressings for four weeks in a primary care setting. The outcomes: ‘Healed ulcer’, ‘Healing ulcer’ or ‘No improvement’ were developed, reflecting the relative reduction in ulcer area from baseline to four weeks of treatment. A data set from a recent meta-analysis, based on four RCTs, was applied to the model. Results Treatment with silver dressings for an initial four weeks was found to give a total cost saving (£141.57) compared with treatment with non-silver dressings. In addition, patients treated with silver dressings had a faster wound closure compared with those who had been treated with non-silver dressings. Conclusion The use of silver dressings improves healing time and can lead to overall cost savings. These results can be used to guide healthcare decision makers in evaluating the economic aspects of treatment with silver dressings in hard-to-heal chronic VLUs

A novel psittacine adenovirus identified during an outbreak of avian chlamydiosis and human psittacosis: zoonosis associated with virus-bacterium coinfection in birds

Chlamydophila psittaci is found worldwide, but is particularly common among psittacine birds in tropical and subtropical regions. While investigating a human psittacosis outbreak that was associated with avian chlamydiosis in Hong Kong, we identified a novel adenovirus in epidemiologically linked Mealy Parrots, which was not present in healthy birds unrelated to the outbreak or in other animals. The novel adenovirus (tentatively named Psittacine adenovirus HKU1) was most closely related to Duck adenovirus A in the Atadenovirus genus. Sequencing showed that the Psittacine adenovirus HKU1 genome consists of 31,735 nucleotides. Comparative genome analysis showed that the Psittacine adenovirus HKU1 genome contains 23 open reading frames (ORFs) with sequence similarity to known adenoviral genes, and six additional ORFs at the 3′ end of the genome. Similar to Duck adenovirus A, the novel adenovirus lacks LH1, LH2 and LH3, which distinguishes it from other viruses in the Atadenovirus genus. Notably, fiber-2 protein, which is present in Aviadenovirus but not Atadenovirus, is also present in Psittacine adenovirus HKU1. Psittacine adenovirus HKU1 had pairwise amino acid sequence identities of 50.3–54.0% for the DNA polymerase, 64.6–70.7% for the penton protein, and 66.1–74.0% for the hexon protein with other Atadenovirus. The C. psittaci bacterial load was positively correlated with adenovirus viral load in the lung. Immunostaining for fiber protein expression was positive in lung and liver tissue cells of affected parrots, confirming active viral replication. No other viruses were found. This is the first documentation of an adenovirus-C. psittaci co-infection in an avian species that was associated with a human outbreak of psittacosis. Viral-bacterial co-infection often increases disease severity in both humans and animals. The role of viral-bacterial co-infection in animal-to-human transmission of infectious agents has not received sufficient attention and should be emphasized in the investigation of disease outbreaks in human and animals. © 2014 To et al.published_or_final_versio

Persistence of magnetic field driven by relativistic electrons in a plasma

The onset and evolution of magnetic fields in laboratory and astrophysical plasmas is determined by several mechanisms, including instabilities, dynamo effects and ultra-high energy particle flows through gas, plasma and interstellar-media. These processes are relevant over a wide range of conditions, from cosmic ray acceleration and gamma ray bursts to nuclear fusion in stars. The disparate temporal and spatial scales where each operates can be reconciled by scaling parameters that enable to recreate astrophysical conditions in the laboratory. Here we unveil a new mechanism by which the flow of ultra-energetic particles can strongly magnetize the boundary between the plasma and the non-ionized gas to magnetic fields up to 10-100 Tesla (micro Tesla in astrophysical conditions). The physics is observed from the first time-resolved large scale magnetic field measurements obtained in a laser wakefield accelerator. Particle-in-cell simulations capturing the global plasma and field dynamics over the full plasma length confirm the experimental measurements. These results open new paths for the exploration and modelling of ultra high energy particle driven magnetic field generation in the laboratory

Cytokine (IL-6) and chemokine (IL-8) gene polymorphisms among rheumatoid arthritis patients in Taiwan

[[abstract]]Objective The involvement of cytokines and chemokines in the pathogenesis of rheumatoid arthritis (RA) is well studied: however, the genetic bases behind this is not well understood. The aim of this study was to examine whether -572 G/C polymorphism in the IL-6 gene and 2767 A/G polymorphism in the 3-untranslated region (UTR) of the IL-8 gene are associated with rheumatoid arthritis (RA). Methods We enrolled 199 RA patients and 130 normal controls. Polymerase chain reaction was used to identify the IL-6-572G/C and IL-8 3-UTR 2767A/G polymorphisms. The relationships between clinical manifestations of RA and the polymorphisms of each gene were investigated by comparing the genotypes among RA patients with different clinical variables. Results We found no significant difference in the genotypic and allelic frequencies of the single nucleotide polymorphisms of IL-6 and IL-8 genes between RA patients and controls. Clinical characteristics such as age at onset, rheumatoid factor positivity, joint erosion and extra-articular manifestations were compared among patients with different genotypes of the IL-6 and IL-8 genes. We found that patients with IL-8 3-UTR 2767AA genotype had a significantly younger age of onset of RA than patients without that genotype. Conclusion The IL-6 -572 G/C and IL-8 3-UTR 2767A/G polymorphisms are not associated with the risk of developing rheumatoid arthritis. However, the finding that patients with IL-8 3-UTR 2767AA developed RA at a younger age suggests that this genotype may influence the etiopathology of RA in patients in Taiwan. Therefore, further single nucleotide polymorphism studies of this 3 UTR region may give more novel findings and understanding of the genetic basis of rheumatoid arthritis

Association of CD4 Enhancer Gene Polymorphisms with Rheumatoid Arthritis and Systemic Lupus Erythematosus in Taiwan

[[abstract]]Objective. It has been found that changes in CD4 expression and CD4+ T cell activity may influence tolerance or tissue destruction in autoimmune diseases and contribute to their risk. We examined whether an association of CD4 enhancer gene polymorphisms with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) exists. Methods. For study of the CD4 -11743A/C polymorphism, 192 patients with RA, 141 patients with SLE, and 96 normal controls participated. For the CD4 -10845A/G polymorphism, 191 patients with RA, 127 patients with SLE, and 92 controls participated. The polymorphism of the CD4 enhancer was examined with the polymerase chain reaction-restriction fragment length polymorphism method. Genotypic and allelic frequencies of the 3 groups of participants were compared. Genotype groups were also compared according to different clinical variables among the patients with RA and SLE. Results. For the CD4 -11743A/C polymorphism, patients with RA demonstrated significantly higher frequency of the C allele (p = 0.048); patients with SLE had significantly higher frequency of the CC genotype (p = 0.026), and lower frequency of the AC genotype (p = 0.013) compared with controls. For the CD4 -10845A/G polymorphism, patients with RA had significantly higher frequencies of the AA genotype (p = 0.047) and the A allele (p = 0.026); patients with SLE had significantly higher frequency of the AA genotype (p = 0.011) and A allele (p = 0.001), and lower frequency of the GG genotype (p = 0.003) compared with controls. A comparison of genotype groups according to different clinical variables revealed the association of the respective polymorphisms with mucosal ulcer lesions among patients with SLE. Conclusion. Our results suggest that the genetic polymorphisms at the CD4 enhancer gene are associated with the risk of development of RA and SLE. They are also associated with mucosal ulcer lesions in patients with SLE