Transport in inhomogeneous quantum critical fluids and in the Dirac fluid in graphene

We develop a general hydrodynamic framework for computing direct current thermal and electric transport in a strongly interacting finite temperature quantum system near a Lorentz-invariant quantum critical point. Our framework is non-perturbative in the strength of long wavelength fluctuations in the background charge density of the electronic fluid, and requires the rate of electron-electron scattering to be faster than the rate of electron-impurity scattering. We use this formalism to compute transport coefficients in the Dirac fluid in clean samples of graphene near the charge neutrality point, and find results insensitive to long range Coulomb interactions. Numerical results are compared to recent experimental data on thermal and electrical conductivity in the Dirac fluid in graphene and substantially improved quantitative agreement over existing hydrodynamic theories is found. We comment on the interplay between the Dirac fluid and acoustic and optical phonons, and qualitatively explain experimentally observed effects. Our work paves the way for quantitative contact between experimentally realized condensed matter systems and the wide body of high energy inspired theories on transport in interacting many-body quantum systems.Comment: 19 + 12 pages; 8 + 3 figures; v2: very minor changes, published versio

Graphene-based Josephson junction single photon detector

We propose to use graphene-based Josephson junctions (gJjs) to detect single photons in a wide electromagnetic spectrum from visible to radio frequencies. Our approach takes advantage of the exceptionally low electronic heat capacity of monolayer graphene and its constricted thermal conductance to its phonon degrees of freedom. Such a system could provide high sensitivity photon detection required for research areas including quantum information processing and radio-astronomy. As an example, we present our device concepts for gJj single photon detectors in both the microwave and infrared regimes. The dark count rate and intrinsic quantum efficiency are computed based on parameters from a measured gJj, demonstrating feasibility within existing technologies.Comment: 11 pages, 6 figures, and 1 table in the main tex

Low Frequency Oscillator

This paper was prepared under the direction of Dr. C. A. Perkins and submitted as a thesis for a degree of Bachelor of Science in Electrical Engineering. It discusses the theory of a three-electrode vacuum tube used as an a.c. power generator; the construction, calibration, and operation of a three-electrode vacuum tube generator of low frequency oscillations, frequencies varying from 200 to 300 cycles per second

Involvement of mast cells in monocrotaline-induced pulmonary hypertension in rats

Background: Mast cells (MCs) are implicated in inflammation and tissue remodeling. Accumulation of lung MCs is described in pulmonary hypertension (PH); however, whether MC degranulation and c-kit, a tyrosine kinase receptor critically involved in MC biology, contribute to the pathogenesis and progression of PH has not been fully explored.Methods: Pulmonary MCs of idiopathic pulmonary arterial hypertension (IPAH) patients and monocrotaline-injected rats (MCT-rats) were examined by histochemistry and morphometry. Effects of the specific c-kit inhibitor PLX and MC stabilizer cromolyn sodium salt (CSS) were investigated in MCT-rats both by the preventive and therapeutic approaches. Hemodynamic and right ventricular hypertrophy measurements, pulmonary vascular morphometry and analysis of pulmonary MC localization/counts/activation were performed in animal model studies.Results: There was a prevalence of pulmonary MCs in IPAH patients and MCT-rats as compared to the donors and healthy rats, respectively. Notably, the perivascular MCs were increased and a majority of them were degranulated in lungs of IPAH patients and MCT-rats (p < 0.05 versus donor and control, respectively). In MCT-rats, the pharmacological inhibitions of MC degranulation and c-kit with CSS and PLX, respectively by a preventive approach (treatment from day 1 to 21 of MCT-injection) significantly attenuated right ventricular systolic pressure (RVSP) and right ventricular hypertrophy (RVH). Moreover, vascular remodeling, as evident from the significantly decreased muscularization and medial wall thickness of distal pulmonary vessels, was improved. However, treatments with CSS and PLX by a therapeutic approach (from day 21 to 35 of MCT-injection) neither improved hemodynamics and RVH nor vascular remodeling.Conclusions: The accumulation and activation of perivascular MCs in the lungs are the histopathological features present in clinical (IPAH patients) and experimental (MCT-rats) PH. Moreover, the accumulation and activation of MCs in the lungs contribute to the development of PH in MCT-rats. Our findings reveal an important pathophysiological insight into the role of MCs in the pathogenesis of PH in MCT- rats

Focus on the Forest, Not the Trees: A Checklist for Planning Chapter Meetings

Author Affiliations: Jon Crossno, MLS, AHIP, Cataloging & Metadata Librarian, University of Texas Southwestern Medical Center, Dallas, Texas; Lisa Traditi, MLS, AHIP, Head of Education and Reference, Health Sciences Library, Anschutz Medical Campus, University of Colorado, Aurora, ColoradoOBJECTIVES: After successfully planning Quint*Essential: Convergence and Collaboration, a meeting of five MLA chapters, the authors share the lessons they learned from their experience. METHODS: Held Oct.12-16, 2014, Quint*Essental was a joint meeting of the Midcontinental Chapter of MLA (MCMLA), Medical Library Group of Southern California & Arizona (MLGSCA), Northern California & Nevada Medical Library Group (NCNMLG), Pacific Northwest Chapter of MLA (PNCMLA), and South Central Chapter of MLA (SCCMLA). After reviewing successes and failures of their multi-chapter meeting, the authors used SurveyMonkey to gather the opinions and advice of other multiple chapter meeting planners. The authors then identified key activities and time-sensitive tasks necessary to planning such a meeting. RESULTS: From this amalgam of information, they created a checklist designed to help future planners, whether for individual or multiple chapter meetings. This checklist also includes a recommended timeline for when essential milestones should be reached. CONCLUSIONS: Holding a multi-chapter meeting, while a daunting task, can be beneficial to chapters and attendees. A vetted planning checklist, along with strong communication, skills with shared decision-making, and effective record-keeping are key components for success

Utilizing Load Shifting for Optimal Compressor Sequencing in Industrial Refrigeration

The ubiquity and energy needs of industrial refrigeration has prompted several research studies investigating various control opportunities for reducing energy demand. This work focuses on one such opportunity, termed compressor sequencing, which entails intelligently selecting the operational state of the compressors to service the required refrigeration load with the least possible work. We first study the static compressor sequencing problem and observe that deriving the optimal compressor operational state is computationally challenging and can vary dramatically based on the refrigeration load. Thus we introduce load shifting in conjunction with compressor sequencing, which entails strategically precooling the facility to allow for more efficient compressor operation. Interestingly, we show that load shifting not only provides benefits in computing the optimal compressor operational state, but also can lead to significant energy savings. Our results are based on and compared to real-world sensor data from an operating industrial refrigeration site of Butterball LLC located in Huntsville, AR, which demonstrated that without load shifting, even optimal compressor operation results in compressors often running at intermediate capacity levels, which can lead to inefficiencies. Through collected data, we demonstrate that a load shifting approach for compressor sequencing has the potential to reduce energy use of the compressors up to 20% compared to optimal sequencing without load shifting

Efficient Industrial Refrigeration Scheduling with Peak Pricing

The widespread use of industrial refrigeration systems across various sectors contribute significantly to global energy consumption, highlighting substantial opportunities for energy conservation through intelligent control design. As such, this work focuses on control algorithm design in industrial refrigeration that minimize operational costs and provide efficient heat extraction. By adopting tools from inventory control, we characterize the structure of these optimal control policies, exploring the impact of different energy cost-rate structures such as time-of-use (TOU) pricing and peak pricing. While classical threshold policies are optimal under TOU costs, introducing peak pricing challenges their optimality, emphasizing the need for carefully designed control strategies in the presence of significant peak costs. We provide theoretical findings and simulation studies on this phenomenon, offering insights for more efficient industrial refrigeration management