Analysis of the gain distribution across the active region of InGaAs-InAlGaAs multiple quantum well lasers

Spectral gain measurements for two InGaAs-InAlGaAs multiple width quantum well structures, with inverse-configured active regions, have been presented. One structure consisted of wide quantum wells near the p-side and narrow quantum wells near the n-side of the active region. The other structure consisted of narrow quantum wells near the p-side of the active region with wider quantum wells near the n-side. It is shown that, for the same operating conditions, the structure with wide quantum wells on the p-side of the active region provided a 15% broader gain spectrum in comparison to the structure with narrow quantum wells on the p-side of the active region. The analysis of the results shows non-uniform carrier distribution across the active region of the structures, where the structure with wide quantum wells near the p-side of the active region provided 65% more gain in comparison to the structure with narrow quantum wells near the p-side of the active region. The gain distribution results have been compared with that obtained for the phosphorous quaternary structures in other literature and have shown there is some evidence to suggest that the gain distribution is more uniform in aluminium quaternary than phosphorous quaternary material

Integration of a resonant tunneling diode and an optical communications laser

We report on the first integration of a resonant tunneling diode and an optical communications laser operating at around 1.5 /spl μm. We demonstrate its low-frequency bistable operation and model its electrical characteristics

Cultivating interpretive thinking through enacting narrative pedagogy

Teachers and educational researchers in nursing have persisted in their attempts to teach students critical thinking and to evaluate the effectiveness of these efforts. Yet, despite the plethora of studies investigating critical thinking, there is a paucity of research providing evidence that teachers’ efforts improve students’ thinking. The purpose of this interpretive phenomenological study is to explicate how students’ thinking can be extended when teachers use Narrative Pedagogy. Specifically, the theme Cultivating Interpretive Thinking refers to how teachers’ use of Narrative Pedagogy moves beyond the critical thinking movement’s emphasis on analytical thinking (ie, problem solving). Cultivating Interpretive Thinking offers an innovative approach for teaching and learning thinking that attends to students’ embodied, reflective, and pluralistic thinking experiences. Teachers who cultivate interpretive thinking add complexity to students’ thinking to better prepare them for challenging, complex, and unpredictable clinical environments

Recent developments in optical fibre based optoelectronic oscillators

The paper reports recent progress on new types of low noise and high spectral purity optoelectronic oscillators operating at optical wavelengths around 1550nm and radio frequencies (RF) up to 40GHz with RF linewidths <1kHz

Human stem cell-derived astrocytes replicate human prions in a PRNP genotype-dependent manner.

Prions are infectious agents that cause neurodegenerative diseases such as Creutzfeldt-Jakob disease (CJD). The absence of a human cell culture model that replicates human prions has hampered prion disease research for decades. In this paper, we show that astrocytes derived from human induced pluripotent stem cells (iPSCs) support the replication of prions from brain samples of CJD patients. For experimental exposure of astrocytes to variant CJD (vCJD), the kinetics of prion replication occur in a prion protein codon 129 genotype-dependent manner, reflecting the genotype-dependent susceptibility to clinical vCJD found in patients. Furthermore, iPSC-derived astrocytes can replicate prions associated with the major sporadic CJD strains found in human patients. Lastly, we demonstrate the subpassage of prions from infected to naive astrocyte cultures, indicating the generation of prion infectivity in vitro. Our study addresses a long-standing gap in the repertoire of human prion disease research, providing a new in vitro system for accelerated mechanistic studies and drug discovery