A low-noise photonic heterodyne synthesizer and its application to millimeter-wave radar.

Microwave photonics offers transformative capabilities for ultra-wideband electronic signal processing and frequency synthesis with record-low phase noise levels. Despite the intrinsic bandwidth of optical systems operating at ~200 THz carrier frequencies, many schemes for high-performance photonics-based microwave generation lack broadband tunability, and experience tradeoffs between noise level, complexity, and frequency. An alternative approach uses direct frequency down-mixing of two tunable semiconductor lasers on a fast photodiode. This form of optical heterodyning is frequency-agile, but experimental realizations have been hindered by the relatively high noise of free-running lasers. Here, we demonstrate a heterodyne synthesizer based on ultralow-noise self-injection-locked lasers, enabling highly-coherent, photonics-based microwave and millimeter-wave generation. Continuously-tunable operation is realized from 1-104 GHz, with constant phase noise of -109 dBc/Hz at 100 kHz offset from carrier. To explore its practical utility, we leverage this photonic source as the local oscillator within a 95-GHz frequency-modulated continuous wave (FMCW) radar. Through field testing, we observe dramatic reduction in phase-noise-related Doppler and ranging artifacts as compared to the radar's existing electronic synthesizer. These results establish strong potential for coherent heterodyne millimeter-wave generation, opening the door to a variety of future applications including high-dynamic range remote sensing, wideband wireless communications, and THz spectroscopy.

West Nile virus range expansion into British Columbia.

In 2009, an expansion of West Nile virus (WNV) into the Canadian province of British Columbia was detected. Two locally acquired cases of infection in humans and 3 cases of infection in horses were detected by ELISA and plaque-reduction neutralization tests. Ten positive mosquito pools were detected by reverse transcription PCR. Most WNV activity in British Columbia in 2009 occurred in the hot and dry southern Okanagan Valley. Virus establishment and amplification in this region was likely facilitated by above average nightly temperatures and a rapid accumulation of degree-days in late summer. Estimated exposure dates for humans and initial detection of WNV-positive mosquitoes occurred concurrently with a late summer increase in Culex tarsalis mosquitoes (which spread western equine encephalitis) in the southern Okanagan Valley. The conditions present during this range expansion suggest that temperature and Cx. tarsalis mosquito abundance may be limiting factors for WNV transmission in this portion of the Pacific Northwest.

Quantum interference of electrically generated single photons from a quantum dot.

Quantum interference lies at the foundation of many protocols for scalable quantum computing and communication with linear optics. To observe these effects the light source must emit photons that are indistinguishable. From a technological standpoint, it would be beneficial to have electrical control over the emission. Here we report of an electrically driven single-photon source emitting indistinguishable photons. The device consists of a layer of InAs quantum dots embedded in the intrinsic region of a p-i-n diode. Indistinguishability of consecutive photons is tested in a two-photon interference experiment under two modes of operation, continuous and pulsed current injection. We also present a complete theory based on the interference of photons with a Lorentzian spectrum which we compare to both our continuous wave and pulsed experiments. In the former case, a visibility was measured limited only by the timing resolution of our detection system. In the case of pulsed injection, we employ a two-pulse voltage sequence which suppresses multi-photon emission and allows us to carry out temporal filtering of photons which have undergone dephasing. The characteristic Hong-Ou-Mandel 'dip' is measured, resulting in a visibility of 64 +/- 4%.

Electrically driven single-photon source.

Electroluminescence from a single quantum dot within the intrinsic region of a p-i-n junction is shown to act as an electrically driven single-photon source. At low injection currents, the dot electroluminescence spectrum reveals a single sharp line due to exciton recombination, while another line due to the biexciton emerges at higher currents. The second-order correlation function of the diode displays anti-bunching under a continuous drive current. Single-photon emission is stimulated by subnanosecond voltage pulses. These results suggest that semiconductor technology can be used to mass-produce a single-photon source for applications in quantum information technology.

An Exploratory Case Study of Mental Toughness Variability and Potential Influencers over 30 Days.

The purpose of this study was to explore whether mental toughness varies across a 30-day training block and whether such variability is associated with specific antecedents. This exploratory case study research investigated mental toughness variability using the Mental Toughness Index (MTI) with thirteen elite master runners across a series of self-selected training sessions, followed by interviews and follow-up questionnaires, to identify primary influencers of variability. There were significant differences in the MTI scores between baseline (before the training period), and the minimum and the maximum reported score over five self-selected training sessions (p's < 0.004). The proceeding follow-up interviews and questionnaires then provided insights into factors influencing this intra-individual variability. These higher-level themes included foundational wellbeing, specific preparation, and actions utilized in the moment. This study is the first to demonstrate within-person MTI variability across specific training sessions and provides initial insights for both athletes and practitioners into potential influencers of mental toughness.

Clinical experience with an integrated continuous glucose sensor/insulin pump platform: a feasibility study.

The recent US Food and Drug Administration approval of an integrated real-time continuous glucose monitoring (CGM) system and insulin pump (Medtronic Mini-Med Paradigm REAL-Time System; Medtronic MiniMed, Inc., Northridge, Calif) is the most recent breakthrough paving the way toward the development of a closedloop insulin delivery system that could revolutionize diabetes care. An early prototype of the MiniMed Paradigm REAL-Time System--which provided both realtime CGM and insulin pump therapy but was not yet fully integrated--was tested in 20 volunteer subjects with type 1 diabetes who wore the device for up to 2 y. Subjects were instructed on the technical use of the device but were provided no additional support, aside from their usual diabetes care. Participation in the trial averaged 317 d (minimum, 88 d; maximum, 618 d). Five participants prematurely dropped out of the study (2 because of the inconvenience of carrying 2 devices). Data from all subjects were analyzed. Subjects reduced their A1C by a mean of 1.1% (standard deviation, 0.8). After 3 mo of device use, the number of participants who achieved A1C <7% increased by more than 3-fold. Individuals with baseline A1C >or= 7% had a 67% likelihood of achieving an A1C <7% by the first follow-up assessment. This observational study of combined CGM and insulin pump therapy suggests that this innovative device can help people achieve improved glycemic control. Given that only about one third of individuals with diabetes are achieving glycemic control targets, more effective methods to help patients avoid the devastating consequences of uncontrolled diabetes are desperately needed.

Microlessons: Toward a History of Information-Age Cuisine.

This essay proposes that critiques of the industrial food system have not kept pace with its rapid transformation through information technologies, and returns to the emergence of microwave cooking during the 1970s for an illustrative case study. Not just the appliances but also their related cookbooks were produced by corporations heavily invested in electronics. Peculiar convergences suggest that a more encompassing approach to the new cuisine is imperative if we are to understand its complex ecology and phenomenology. In deference to a term from one such cookbook published by General Electric, my history is organized around eight related "Microlessons"-each an invented culinary technique, procedure, or adaptation responding to challenges posed by the new technology-that in hindsight are difficult to confine under the rubric of food studies. The aim is to articulate a new perspective on the post-industrial food system and its many consequences.

Continuous glucose monitoring--a study of the Enlite sensor during hypo- and hyperbaric conditions.

BACKGROUND: The performance and accuracy of the Enlite(™) (Medtronic, Inc., Northridge, CA) sensor may be affected by microbubble formation at the electrode surface during hypo- and hyperbaric conditions. The effects of acute pressure changes and of prewetting of sensors were investigated. MATERIALS AND METHODS: On Day 1, 24 sensors were inserted on the right side of the abdomen and back in one healthy individual; 12 were prewetted with saline solution, and 12 were inserted dry. On Day 2, this procedure was repeated on the left side. All sensors were attached to an iPro continuous glucose monitoring (CGM) recorder. Hypobaric and hyperbaric tests were conducted in a pressure chamber, with each test lasting 105 min. Plasma glucose values were obtained at 5-min intervals with a HemoCue(®) (Ängelholm, Sweden) model 201 glucose analyzer for comparison with sensor glucose values. RESULTS: Ninety percent of the CGM systems operated during the tests. The mean absolute relative difference was lower during hyperbaric than hypobaric conditions (6.7% vs. 14.9%, P<0.001). Sensor sensitivity was slightly decreased (P<0.05) during hypobaric but not during hyperbaric conditions. Clarke Error Grid Analysis showed that 100% of the values were found in the A+B region. No differences were found between prewetted and dry sensors. CONCLUSIONS: The Enlite sensor performed adequately during acute pressure changes and was more accurate during hyperbaric than hypobaric conditions. Prewetting the sensors did not improve accuracy. Further studies on type 1 diabetes subjects are needed under various pressure conditions.