School Leadership Interventions Under the Every Student Succeeds Act: Evidence Review - Updated and Expanded

This RAND analysis offers guidance to states and districts on how they can choose to use the Every Student Succeeds Act to help achieve their school improvement goals by supporting principals and other school leaders

Hybrid GaN LED with capillary-bonded II–VI MQW color-converting membrane for visible light communications

The rapid emergence of gallium-nitride (GaN) light-emitting diodes (LEDs) for solid-state lighting has created a timely opportunity for optical communications using visible light. One important challenge to address this opportunity is to extend the wavelength coverage of GaN LEDs without compromising their modulation properties. Here, a hybrid source for emission at 540 nm consisting of a 450 nm GaN micro-sized LED (micro-LED) with a micron-thick ZnCdSe/ZnCdMgSe multi-quantum-well color-converting membrane is reported. The membrane is liquid-capillary-bonded directly onto the sapphire window of the micro-LED for full hybridization. At an injection current of 100 mA, the color-converted power was found to be 37 μW. At this same current, the −3 dB optical modulation bandwidth of the bare GaN and hybrid micro-LEDs were 79 and 51 MHz, respectively. The intrinsic bandwidth of the color-converting membrane was found to be power-density independent over the range of the micro-LED operation at 145 MHz, which corresponds to a mean carrier lifetime of 1.9 ns

Combined surgical and endovascular treatment of a spontaneous diploic arteriovenous fistula

✓The authors report on the case of a 28-year-old woman presenting with an intraosseous arteriovenous fistula (AVF) located in the left parietal bone. The fistula was formed by direct arteriovenous shunts connecting branches of the left middle meningeal and superficial temporal arteries with a parietal diploic vein. Drainage occurred through both the external and internal jugular venous systems. Therapy consisted of combined surgical and endovascular approaches. The results of a pathological examination of the resected AVF showed mild enlargement of the diploic space. The angiographic appearance, pathological anatomy, and treatment of this rare lesion are discussed, as is a possible relationship between diploic AVFs and the development of aneurysm bone cysts.</jats:p

Evaluation of Delaware Stars for Early Success

As a first step in a larger study of Delaware Stars, a voluntary quality rating and improvement system (QRIS) for early learning and care programs, RAND researchers examined prior QRIS validation research, analyzed Delaware Stars administrative data, conducted key stakeholder interviews and focus groups, and implemented a virtual pilot test using national data to identify relationships between program quality and child developmental outcomes

Growth and characterization of ZnCdMgSe-based green light emitters and distributed Bragg reflectors towards II–VI based semiconductor disk lasers

We report the structural and optical properties of molecular beam epitaxy grown II–VI semiconductor multiple quantum well (MQW) structures and distributed Bragg reflector (DBR) on InP substrates for application in developing optically-pumped semiconductor disk lasers (SDLs) operating in the green spectral range. One sample was grown directly on an InP substrate with an InGaAs buffer layer, while another had a 5-period ZnCdMgSe-based DBR grown on the InGaAs/InP substrate. X-ray diffraction and scanning electron microscopy measurements revealed sharp superlattice peaks and abrupt layer interfaces, while steady-state photoluminescence measurements demonstrated surface emission between 540–570 nm. Under pulsed excitation both samples exhibited features of amplified spontaneous emission (ASE) or stimulated emission, accompanied by luminescence lifetime shortening. The sample with the DBR showed higher surface luminescence and the onset of ASE at lower pump power. To further explore the design and performance of a ZnCdMgSe-based DBR, a 20-period DBR was grown and a reflectivity of 83% was obtained at ∼560 nm. We estimate that a DBR with ∼40 periods would be needed for optimal performance in a SDL using these materials. These results show the potential of II–VI MQW structures on InP substrates for the development of SDLs operational in the green–yellow wavelength range

Processing and characterisation of II–VI ZnCdMgSe thin film gain structures

AbstractLattice-matched II–VI selenide quantum well (QW) structures grown on InP substrates can be designed for emission throughout the visible spectrum. InP has, however, strong visible-light absorption, so that a method for epitaxial lift-off and transfer to transparent substrates is desirable for vertically-integrated devices. We have designed and grown, via molecular beam epitaxy, ZnCdSe/ZnCdMgSe multi-QW gain regions for vertical emission, with the QWs positioned for resonant periodic gain. The release of the 2.7μm-thick ZnCdSe/ZnCdMgSe multi-QW film is achieved via selective wet etching of the substrate and buffer layers leaving only the epitaxial layers, which are subsequently transferred to transparent substrates, including glass and thermally-conductive diamond. Post-transfer properties are investigated, with power and temperature-dependent surface- and edge-emitting photoluminescence measurements demonstrating no observable strain relaxation effects or significant shift in comparison to unprocessed samples. The temperature dependent QW emission shift is found experimentally to be 0.13nm/K. Samples capillary-bonded epitaxial-side to glass exhibited a 6nm redshift under optical pumping of up to 35mW at 405nm, corresponding to a 46K temperature increase in the pumped region; whereas those bonded to diamond exhibited no shift in QW emission, and thus efficient transfer of the heat from the pumped region. Atomic force microscopy analysis of the etched surface reveals a root-mean-square roughness of 3.6nm. High quality optical interfaces are required to establish a good thermal and optical contact for high power optically pumped laser applications