Circuit Theory

Contains reports on two research projects.Lincoln Laboratory, Purchase Order DDL-B222U.S. Air Force under Air Force Contract AF19(604)-520

Widely tunable, non-degenerate three-wave mixing microwave device operating near the quantum limit

We present the first experimental realization of a widely frequency tunable, non-degenerate three-wave mixing device for quantum signals at GHz frequency. It is based on a new superconducting building-block consisting of a ring of four Josephson junctions shunted by a cross of four linear inductances. The phase configuration of the ring remains unique over a wide range of magnetic fluxes threading the loop. It is thus possible to vary the inductance of the ring with flux while retaining a strong, dissipation-free, and noiseless non-linearity. The device has been operated in amplifier mode and its noise performance has been evaluated by using the noise spectrum emitted by a voltage biased tunnel junction at finite frequency as a test signal. The unprecedented accuracy with which the crossover between zero-point-fluctuations and shot noise has been measured provides an upper-bound for the noise and dissipation intrinsic to the device.Comment: Accepted for Physical Review Letters. Supplementary material can be found in the source packag

W-band 0.3W PHEMT MMIC power amplifier module

A compact (1.8 by 3.0 by 3.8 cm) WR-10 waveguide amplifier module providing 310-mW power output, 20-dB gain, and 5 GHz of 1-dB bandwidth at a center frequency of 96 GHz is described. The module is comprised of 22 identical PHEMT chips, 4-way microstrip power combiners and dividers, and a 4-way waveguide power combiner

Circuit Theory

Contains reports on three research projects.Lincoln Laboratory (Purchase Order DDL-B222)United States Department of the ArmyUnited States Department of the NavyUnited States Department of the Air Force (Contract AF19(604)-5200

Impact of a family medicine resident wellness curriculum: a feasibility study

BACKGROUND: Up to 60% of practicing physicians report symptoms of burnout, which often peak during residency. Residency is also a relevant time for habits of self-care and resiliency to be emphasized. A growing literature underscores the importance of this; however, evidence about effective burnout prevention curriculum during residency remains limited. OBJECTIVES: The purpose of this project is to evaluate the impact of a new, 1-month wellness curriculum for 12 second-year family medicine residents on burnout, empathy, stress, and self-compassion. METHODS: The pilot program, introduced during a new rotation emphasizing competencies around leadership, focused on teaching skills to cultivate mindfulness and self-compassion in order to enhance empathy and reduce stress. Pre-assessments and 3-month follow-up assessments on measures of burnout, empathy, self-compassion, and perceived stress were collected to evaluate the impact of the curriculum. It was hypothesized that this curriculum would enhance empathy and self-compassion as well as reduce stress and burnout among family medicine residents. RESULTS: Descriptive statistics revealed positive trends on the mean scores of all the measures, particularly the Mindfulness Scale of the Self-Compassion Inventory and the Jefferson Empathy Scale. However, the small sample size and lack of sufficient power to detect meaningful differences limited the use of inferential statistics. CONCLUSIONS: This feasibility study demonstrates how a residency wellness curriculum can be developed, implemented, and evaluated with promising results, including high participant satisfaction

Infants Exposed To Homelessness: Health, Health Care Use, And Health Spending From Birth To Age Six

Homeless infants are known to have poor birth outcomes, but the longitudinal impact of homelessness on health, health care use, and health spending during the early years of life has received little attention. Linking Massachusetts emergency shelter enrollment records for the period 2008-15 with Medicaid claims, we compared 5,762 infants who experienced a homeless episode with a group of 5,553 infants matched on sex, race/ethnicity, location, and birth month. Infants born during a period of unstable housing resulting in homelessness had higher rates of low birthweight, respiratory problems, fever, and other common conditions; longer neonatal intensive care unit stays; more emergency department visits; and higher annual spending. Differences in most health conditions persisted for two to three years. Asthma diagnoses, emergency department visits, and spending were significantly higher through age six. While screening and access to health care can be improved for homeless infants, long-term solutions require a broader focus on housing and income

In Silico Generation of Alternative Hypotheses Using Causal Mapping (CMAP)

Previously, we introduced causal mapping (CMAP) as an easy to use systems biology tool for studying the behavior of biological processes that occur at the cellular and molecular level. CMAP is a coarse-grained graphical modeling approach in which the system of interest is modeled as an interaction map between functional elements of the system, in a manner similar to portrayals of signaling pathways commonly used by molecular cell biologists. CMAP describes details of the interactions while maintaining the simplicity of other qualitative methods (e.g., Boolean networks)

Terahertz hot electron bolometer waveguide mixers for GREAT

Supplementing the publications based on the first-light observations with the German Receiver for Astronomy at Terahertz frequencies (GREAT) on SOFIA, we present background information on the underlying heterodyne detector technology. We describe the superconducting hot electron bolometer (HEB) detectors that are used as frequency mixers in the L1 (1400 GHz), L2 (1900 GHz), and M (2500 GHz) channels of GREAT. Measured performance of the detectors is presented and background information on their operation in GREAT is given. Our mixer units are waveguide-based and couple to free-space radiation via a feedhorn antenna. The HEB mixers are designed, fabricated, characterized, and flight-qualified in-house. We are able to use the full intermediate frequency bandwidth of the mixers using silicon-germanium multi-octave cryogenic low-noise amplifiers with very low input return loss. Superconducting HEB mixers have proven to be practical and sensitive detectors for high-resolution THz frequency spectroscopy on SOFIA. We show that our niobium-titanium-nitride (NbTiN) material HEBs on silicon nitride (SiN) membrane substrates have an intermediate frequency (IF) noise roll-off frequency above 2.8 GHz, which does not limit the current receiver IF bandwidth. Our mixer technology development efforts culminate in the first successful operation of a waveguide-based HEB mixer at 2.5 THz and deployment for radioastronomy. A significant contribution to the success of GREAT is made by technological development, thorough characterization and performance optimization of the mixer and its IF interface for receiver operation on SOFIA. In particular, the development of an optimized mixer IF interface contributes to the low passband ripple and excellent stability, which GREAT demonstrated during its initial successful astronomical observation runs.Comment: Accepted for publication in A&A (SOFIA/GREAT special issue

Quantum tunneling Sb-heterostructure millimeter-wave diodes

We have developed a new zero bias millimeter wave diode based on quantum tunneling in an InAs/AlSb/GaSb nanostructure. It is ideal for square law radiometry and passive millimeter wave imaging. Excellent sensitivity has been demonstrated at present up to 110 GHz, with higher bandwidth predicted for smaller area diodes

Visinets: A Web-Based Pathway Modeling and Dynamic Visualization Tool

In this report we describe a novel graphically oriented method for pathway modeling and a software package that allows for both modeling and visualization of biological networks in a user-friendly format. The Visinets mathematical approach is based on causal mapping (CMAP) that has been fully integrated with graphical interface. Such integration allows for fully graphical and interactive process of modeling, from building the network to simulation of the finished model. To test the performance of Visinets software we have applied it to: a) create executable EGFR-MAPK pathway model using an intuitive graphical way of modeling based on biological data, and b) translate existing ordinary differential equation (ODE) based insulin signaling model into CMAP formalism and compare the results. Our testing fully confirmed the potential of the CMAP method for broad application for pathway modeling and visualization and, additionally, showed significant advantage in computational efficiency. Furthermore, we showed that Visinets web-based graphical platform, along with standardized method of pathway analysis, may offer a novel and attractive alternative for dynamic simulation in real time for broader use in biomedical research. Since Visinets uses graphical elements with mathematical formulas hidden from the users, we believe that this tool may be particularly suited for those who are new to pathway modeling and without the in-depth modeling skills often required when using other software packages