Cavity-Enhanced Emission from a Silicon T Center.

Silicon T centers present the promising possibility of generating optically active spin qubits in an all-silicon device. However, these color centers exhibit long excited state lifetimes and a low Debye-Waller factor, making them dim emitters with low efficiency into the zero-phonon line. Nanophotonic cavities can solve this problem by enhancing radiative emission into the zero-phonon line through the Purcell effect. In this work, we demonstrate cavity-enhanced emission from a single T center in a nanophotonic cavity. We achieve a 2 order of magnitude increase in the brightness of the zero-phonon line relative to waveguide-coupled emitters, a 23% collection efficiency from emitter to fiber, and an overall emission efficiency into the zero-phonon line of 63.4%. We also observe a lifetime enhancement of 5, corresponding to a Purcell factor exceeding 18 when correcting for the emission to the phonon sideband. These results pave the way toward efficient spin-photon interfaces in silicon photonics.

Bright Telecom-Wavelength Single Photons Based on a Tapered Nanobeam.

Telecom-wavelength single photons are essential components for long-distance quantum networks. However, bright and pure single photon sources at telecom wavelengths remain challenging to achieve. Here, we demonstrate a bright telecom-wavelength single photon source based on a tapered nanobeam containing InAs/InP quantum dots. The tapered nanobeam enables directional and Gaussian-like far-field emission of the quantum dots. As a result, using above-band excitation we obtain an end-to-end brightness of 4.1 ± 0.1% and first-lens brightness of 27.0 ± 0.1% at the ∼1300 nm wavelength. Furthermore, we adopt quasi-resonant excitation to reduce both multiphoton emission and decoherence from unwanted charge carriers. As a result, we achieve a coherence time of 523 ± 16 ps and postselected Hong-Ou-Mandel visibility of 0.91 ± 0.09 along with a comparable first-lens brightness of 21.0 ± 0.1%. These results represent a major step toward a practical fiber-based single photon source at telecom wavelengths for long-distance quantum networks.

Auditory brainstem response testing using intranasal dexmedetomidine sedation in children: a pilot study.

OBJECTIVE: Auditory brainstem response (ABR) is used to determine hearing thresholds in children who cannot undergo behavioural testing. Children must remain still during testing, with general anaesthesia (GA) in theatre required for those who cannot. We developed a protocol whereby an ABR was undertaken in a ward environment using only intranasal dexmedetomidine for sedation. DESIGN: Prospective data were collected including the time of sedation onset, ABR duration and arrival to discharge time was recorded and feedback was requested using a questionnaire. STUDY SAMPLE: Twenty-nine consecutive patients routinely undergoing an ABR. RESULTS: From this pilot study, we demonstrated that intranasal dexmedetomidine could be used successfully to administer safe sedation to all twenty-nine children undergoing an ABR in a ward environment as opposed to theatre. CONCLUSIONS: This allowed for faster time to discharge compared to GA, produced what was felt to be a better quality ABR trace, better utilization of a theatre slot, negated the need for GA in a child and created a less stressful experience for both parent and child according to information from feedback questionnaires.

SPRC19: A Database of State Policy Responses to COVID-19 in the United States.

SPRC19 is a new database that seeks to capture a wide range of state policy actions in response to COVID-19 in the United States. Since March 2020 we have monitored state governments' and multi-state associations' websites for executive orders, agency rules, new legislation, and court decisions. We categorize each policy action into one of 206 distinct policies, then document the branch of government, source document, announcement date, implementation date, and expiration date (if applicable). We also record whether the action represents the introduction of a new policy or the expansion or contraction of an existing policy. The current release of SPRC19, v3.0, captures over 13,000 distinct policy actions through April 2020, which constitutes thousands more actions than similar resources over the same time period.

Synchronous and metachronous ureteric metastases from adenocarcinoma of the colon.

Primary adenocarcinoma of the ureter occurs in only <1%. Furthermore, metastatic carcinoma to the ureter is very rare and has been described to occur from breast, lung, stomach and prostate cancers. However, metastases to the ureter from colon cancers are extremely rare, and have been largely reported as incidental post-mortem cases. We describe two cases of asymptomatic ureteric metastases secondary to adenocarcinoma of the colon; one is synchronous, whilst the other is a metachronous ureteric metastasis. With the increasing use of radiological imaging modalities such as CT and MRI (Clin Imaging 2001;25:197-202, 2001), together with increasing survival rates of primary cancers, asymptomatic ureteric metastases are more likely to be diagnosed. In summary, metastatic ureteric carcinoma of colonic origin must be considered as a differential diagnosis when there is a radiological abnormality of the ureter in patients with a history of adenocarcinoma of the colon. This should be considered even in patients with colon adenocarcinoma who have previously undergone adjuvant chemotherapy with curative intent.

Validation of population-based disease simulation models: a review of concepts and methods.

BACKGROUND: Computer simulation models are used increasingly to support public health research and policy, but questions about their quality persist. The purpose of this article is to review the principles and methods for validation of population-based disease simulation models. METHODS: We developed a comprehensive framework for validating population-based chronic disease simulation models and used this framework in a review of published model validation guidelines. Based on the review, we formulated a set of recommendations for gathering evidence of model credibility. RESULTS: Evidence of model credibility derives from examining: 1) the process of model development, 2) the performance of a model, and 3) the quality of decisions based on the model. Many important issues in model validation are insufficiently addressed by current guidelines. These issues include a detailed evaluation of different data sources, graphical representation of models, computer programming, model calibration, between-model comparisons, sensitivity analysis, and predictive validity. The role of external data in model validation depends on the purpose of the model (e.g., decision analysis versus prediction). More research is needed on the methods of comparing the quality of decisions based on different models. CONCLUSION: As the role of simulation modeling in population health is increasing and models are becoming more complex, there is a need for further improvements in model validation methodology and common standards for evaluating model credibility.