Primary cerebellopontine angle melanocytoma: review.

Introduction Primary cerebellopontine angle melanocytomas (PCPAMs) are very rare. Their natural history and prognosis are not fully understood. We reviewed the literature and add a new case to analyze PCPAM's presentation, radiological features, and outcome of treatment. Methods We performed a literature review using Medline, Embase, PubMed, and Cochrane databases. We searched for melanocytoma, melanoma, and pigmented tumors in the posterior cranial fossa and CPA to identify PCPAM. We have also searched our institution's neuro-oncology database. Results We identified 23 PCPAM from the literature and one case of our own. The mean age at presentation was 44.4 years with slight male preponderance. PCPAM presented with cerebellopontine angle (CPA) syndrome with or without hydrocephalus. Preoperative diagnosis was difficult; they appeared hyperintense on T1 and isointense on T2 magnetic resonance imaging (MRI) and enhanced with gadolinium. However, the final diagnosis was only made by immunohistochemical examination. Total surgical resection of PCPAM was associated with prolonged survival while subtotal excision was associated with frequent recurrence. Conclusion PCPAM are very rare and should be considered in the differential diagnosis of all CPA lesions that appear hyperintense on T1 and isointense on T2 MRI images. Patients with PCPAM should undergo total surgical resection to avoid fatal recurrences

Mainstreaming quality and safety: a reformulation of quality and safety education for health professions students

The urgent need to expand the ability of health professionals to improve the quality and safety of patient care in the USA has been well documented. Yet the current methods of teaching quality and safety to health professionals are inadequate for the task. To the extent that quality and safety are addressed at all, they are taught using pedagogies with a narrow focus on content transmission, didactic sessions that are spatially and temporally distant from clinical work, and quality and safety projects segregated from the provision of actual patient care. In this article an argument for a transformative reorientation in quality and safety education for health professions is made. This transformation will require new pedagogies in which a) quality improvement is an integral part of all clinical encounters, b) health professions students and their clinical teachers become co-learners working together to improve patient outcomes and systems of care, c) improvement work is envisioned as the interdependent collaboration of a set of professionals with different backgrounds and perspectives skilfully optimising their work processes for the benefit of patients, and d) assessment in health professions education focuses on not just individual performance but also how the care team's patients fared and how the systems of care were improved

Modeling of light-sensitive resonant-tunneling-diode devices

We present a method to include the effects of light excitation on two different models of resonant-tunneling-diode-based devices. Our approach takes into account both photoconductive and charge accumulation effects responsible for shifting the static I –V curve when the structure is under light excitation. Computational simulations led to good agreement between the model and experimental result

Challenging the orthodoxy: union learning representatives as organic intellectuals

Teacher education and continuing professional development have become a key areas of controversy in England since the period of school sector restructuring following the 1988 Education Reform Act. More recently teacher training and professional development have often been used to promote and reinforce a narrow focus on the government’s ‘standards agenda’. However, the emerging discourse of ‘new professionalism’ has raised the profile of professional development in schools, and together with union learning representatives, there are opportunities to secure real improvements in teachers’ access to continuing professional development. This paper argues however that union learning representatives must go beyond advocating for better access to professional development and should raise more fundamental questions about the nature of professional development and the education system it serves. Drawing on Gramsci’s notion of the ‘organic intellectual’, the paper argues that union learning representatives have a key role as organisers of ideas – creating spaces in which the ideological dominance of current policy orthodoxy might be challenged

Time-Domain All-Optical Demultiplexing With A Semiconductor Directional Coupler

We report the demonstration of demultiplexing of 150 fs pulses, without pulse breakup, in an AlGaAs nonlinear directional coupler operated at photon energies below half the band gap energy of AlGaAs

Ultrafast All-Optical Switching In Gaalas Directional-Couplers At 1.55 Mu-M Without Multiphoton Absorption

We demonstrate ultrafast, high throughput, all-optical switching in optimized, 2-cm-long, half- and full-beat-length nonlinear directional couplers operated at 1.55 mum, below half the band gap of Ga0.82Al0.18As. The long device length allowed the elimination of nonlinear loss and resulted in a switching peak power and energy of 85 W and 65 pJ, respectively

Ultrafast All-Optical Switching In Semiconductor Nonlinear Directional-Couplers At Half The Band-Gap

Efficient ultrafast all-optical switching in nonlinear directional couplers made of AlGaAs and AlGaAs/GaAs quantum wells near half the band gap is reported. The switching is limited by multiphoton absorption which is dominated by three-photon absorption in this spectral range. The three-photon absorption in the quantum well nonlinear directional coupler is stronger than that of bulk AlGaAs. Autocorrelations of the output pulses in the bar and cross states confirm pulse breakup through nonlinear coupling, and illustrate the effects of multiphoton absorption. All sets of experimental data are fitted well by a theoretical model

Optical modulation in a resonant tunneling relaxation oscillator

We report high-speed optical modulation in a resonant tunneling relaxation oscillator consisting of a resonant tunneling diode (RTD) integrated with a unipolar optical waveguide and incorporated in a package with a coplanar waveguide transmission line. When appropriately biased, the RTD can provide wide-bandwidth electrical gain. For wavelengths near the material band edge, small changes of the applied voltage give rise to large, high-speed electroabsorption modulation of the light. We have observed optical modulation at frequencies up to 14 GHz, associated with subharmonic injection locking of the RTD oscillation at the fundamental mode of the coplanar transmission line, as well as generation of 33 ps optical pulses due to relaxation oscillation

Optical modulation at around 1550 nm in an InGaAlAs optical waveguide containing an InGaAs/AlAs resonant tunneling diode

We report electroabsorption modulation of light at around 1550 nm in a unipolar InGaAlAs optical waveguide containing an InGaAs/AlAs double-barrier resonant tunneling diode ~RTD!. The RTD peak-to-valley transition increases the electric field across the waveguide, which shifts the core material absorption band edge to longer wavelengths via the Franz–Keldysh effect, thus changing the light-guiding characteristics of the waveguide. Low-frequency characterization of a device shows modulation up to 28 dB at 1565 nm. When dc biased close to the negative differential conductance region, the RTD optical waveguide behaves as an electroabsorption modulator integrated with a wide bandwidth electrical amplifier, offering a potential advantage over conventional pn modulators