A Case-based Review of Abdominal (and a Few Thoracic) Emergencies and Urgencies Using Single-shot MR.

The rapid evolution of MR scanners and pulse sequence design brings an ever-expanding arsenal of diagnostic tools to radiology departments. However, this increasing abundance of diagnostic tools accentuates the challenge of using new technology efficiently and wisely-that is, to employ what may help diagnosis and/or management, but discards what has a poor likelihood of aiding patient care. This article aims to highlight practical points regarding MR pulse sequences for the evaluation of common emergencies in body imaging through case examples.

Type-II superlattices base visible/extended short-wavelength infrared photodetectors with a bandstructure-engineered photo-generated carrier extractor.

Visible/extended short-wavelength infrared photodetectors with a bandstructure-engineered photo-generated carrier extractor based on type-II InAs/AlSb/GaSb superlattices have been demonstrated. The photodetectors are designed to have a 100% cut-off wavelength of ~2.4 µm at 300K, with sensitivity down to visible wavelengths. The photodetectors exhibit room-temperature (300K) peak responsivity of 0.6 A/W at ~1.7 µm, corresponding to a quantum efficiency of 43% at zero bias under front-side illumination, without any anti-reflection coating where the visible cut-on wavelength of the devices is <0.5 µm. With a dark current density of 5.3 × 10-4 A/cm2 under -20 mV applied bias at 300K, the photodetectors exhibit a specific detectivity of 4.72 × 1010 cm·Hz1/2/W. At 150K, the photodetectors exhibit a dark current density of 1.8 × 10-10 A/cm2 and a quantum efficiency of 40%, resulting in a detectivity of 5.56 × 1013 cm·Hz1/2/W.

Recent progress of quantum cascade laser research from 3 to 12 µm at the Center for Quantum Devices [Invited].

The quantum cascade laser (QCL) is becoming the leading laser source in the mid-infrared (mid-IR) range, which contains two atmospheric transmission windows and many molecular fingerprint absorption features. Since its first demonstration in 1994, the QCL has undergone tremendous development in terms of the output power, wall plug efficiency, wavelength coverage, tunability and beam quality. At the Center for Quantum Devices, we have demonstrated high-power continuous wave operation of QCLs covering a wide wavelength range from 3 to 12 µm, with power output up to 5.1 W at room temperature. Recent research has resulted in power scaling in pulsed mode with up to 203 W output, electrically tunable QCLs based on monolithic sampled grating design, heterogeneous QCLs with a broad spectral gain, broadly tunable on-chip beam-combined QCLs, QCL-based mid-IR frequency combs, and fundamental mode surface emitting quantum cascade ring lasers. The developed QCLs will be the basis for a number of next-generation spectroscopy and sensing systems.

Author Correction: Radiative recombination of confined electrons at the MgZnO/ZnO heterojunction interface.

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

Radiative recombination of confined electrons at the MgZnO/ZnO heterojunction interface.

We investigate the optical signature of the interface in a single MgZnO/ZnO heterojunction, which exhibits two orders of magnitude lower resistivity and 10 times higher electron mobility compared with the MgZnO/Al2O3 film grown under the same conditions. These impressive transport properties are attributed to increased mobility of electrons at the MgZnO/ZnO heterojunction interface. Depth-resolved cathodoluminescence and photoluminescence studies reveal a 3.2 eV H-band optical emission from the heterointerface, which exhibits excitonic properties and a localization energy of 19.6 meV. The emission is attributed to band-bending due to the polarization discontinuity at the interface, which leads to formation of a triangular quantum well and localized excitons by electrostatic coupling.

Nanoselective area growth of defect-free thick indium-rich InGaN nanostructures on sacrificial ZnO templates.

Nanoselective area growth (NSAG) by metal organic vapor phase epitaxy of high-quality InGaN nanopyramids on GaN-coated ZnO/c-sapphire is reported. Nanopyramids grown on epitaxial low-temperature GaN-on-ZnO are uniform and appear to be single crystalline, as well as free of dislocations and V-pits. They are also indium-rich (with homogeneous 22% indium incorporation) and relatively thick (100 nm). These properties make them comparable to nanostructures grown on GaN and AlN/Si templates, in terms of crystallinity, quality, morphology, chemical composition and thickness. Moreover, the ability to selectively etch away the ZnO allows for the potential lift-off and transfer of the InGaN/GaN nanopyramids onto alternative substrates, e.g. cheaper and/or flexible. This technology offers an attractive alternative to NSAG on AlN/Si as a platform for the fabrication of high quality, thick and indium-rich InGaN monocrystals suitable for cheap, flexible and tunable light-emitting diodes.

Monolithically, widely tunable quantum cascade lasers based on a heterogeneous active region design.

Quantum cascade lasers (QCLs) have become important laser sources for accessing the mid-infrared (mid-IR) spectral range, achieving watt-level continuous wave operation in a compact package at room temperature. However, up to now, wavelength tuning, which is desirable for most applications, has relied on external cavity feedback or exhibited a limited monolithic tuning range. Here we demonstrate a widely tunable QCL source over the 6.2 to 9.1 µm wavelength range with a single emitting aperture by integrating an eight-laser sampled grating distributed feedback laser array with an on-chip beam combiner. The laser gain medium is based on a five-core heterogeneous QCL wafer. A compact tunable laser system was built to drive the individual lasers within the array and produce any desired wavelength within the available spectral range. A rapid, broadband spectral measurement (520 cm(-1)) of methane using the tunable laser source shows excellent agreement to a measurement made using a standard low-speed infrared spectrometer. This monolithic, widely tunable laser technology is compact, with no moving parts, and will open new opportunities for MIR spectroscopy and chemical sensing.

Al(x)Ga(1-x)N-based deep-ultraviolet 320×256 focal plane array.

We report the synthesis, fabrication, and testing of a 320×256 focal plane array (FPA) of back-illuminated, solar-blind, p-i-n, Al(x)Ga(1-x)N-based detectors, fully realized within our research laboratory. We implemented a pulse atomic layer deposition technique for the metalorganic chemical vapor deposition growth of thick, high-quality, crack-free, high Al composition Al(x)Ga(1-x)N layers. The FPA is hybridized to a matching ISC 9809 readout integrated circuit and operated in a SE-IR camera system. Solar-blind operation is observed throughout the array with peak detection occurring at wavelengths of 256 nm and lower, and falling off three orders of magnitude by ~285 nm. By developing an opaque masking technology, the visible response of the ROIC is significantly reduced; thus the need for external filtering to achieve solar- and visible-blind operation is eliminated. This allows the FPA to achieve high external quantum efficiency (EQE); at 254 nm, average pixels showed unbiased peak responsivity of 75 mA/W, which corresponds to an EQE of ~37%. Finally, the uniformity of the FPA and imaging properties are investigated.

Type-II superlattice dual-band LWIR imager with M-barrier and Fabry-Perot resonance.

We report a high performance long-wavelength IR dual-band imager based on type-II superlattices with 100% cutoff wavelengths at 9.5 µm (blue channel) and 13 µm (red channel). Test pixels reveal background-limited behavior with specific detectivities as high as ~5×10¹¹ Jones at 7.9 µm in the blue channel and ~1×10¹¹ Jones at 10.2 µm in the red channel at 77 K. These performances were attributed to low dark currents thanks to the M-barrier and Fabry-Perot enhanced quantum efficiencies despite using thin 2 µm absorbing regions. In the imager, the high signal-to-noise ratio contributed to median noise equivalent temperature differences of ~20 milli-Kelvin for both channels with integration times on the order of 0.5 ms, making it suitable for high speed applications.

Unrecognized magic mushroom abuse in a 28-year-old man.

A 28-year-old man with a history of drug and alcohol abuse presented multiple times to the hospital over 2 months with an elusive constellation of symptoms, resolving spontaneously in each instance. This patient required a high level of care for management and stabilization, including 3 emergency department visits, 2 medical floor admissions, and 1 intensive care unit admission. In both the emergency department and inpatient setting, all laboratory and imaging study results, including gas chromatography/mass spectrophotometry of the urine, were negative/normal. A definitive diagnosis eluded multiple emergency medicine, critical care, and consulting physicians. His symptoms included altered mental status, vomiting, diaphoresis, and mydriasis. The patient later admitted using mushrooms to a nurse. In the absence of confirmatory testing, but supported by exclusionary and anecdotal data, we believe that our patient's symptoms are consistent with Psilocybe mushroom toxicity. We feel that had this been considered initially, the correct diagnosis would have led to a better utilization of resources, and we want to remind emergency physicians of the possibility of mushroom abuse in any similar clinical setting.