55 research outputs found
Design and Analysis of High-Frequency Quartz Crystal Microbalance Sensor Array with Concentric Electrodes and Dual Inverted Mesa Structure for Multiple Gas Detection
Lung Cancer is one of the most deadly diseases which claim millions of lives all around the world every year. One of the major reasons that make the treatment process of lung cancer hard is that the patients are diagnosed only during the later stages. Lung cancer patients exhales volatile organic compounds in their breath in low concentration even during the early stages of the disease. There are many gas sensors available to detect these volatiles. However, there are certain disadvantages which make most of the conventional gas sensors unsuitable for early detection. Quartz crystal microbalance (QCM) is one of the promising candidates for volatile organic compounds detection. This thesis describes the design and analysis of the high-frequency quartz crystal microbalance sensor array with a novel concentric electrode and dual inverted mesa structure. Conventional QCM sensors are limited with circular electrodes and single channel design which limits the sensing ability. The proposed QCM sensor array has advantages of a uniform displacement profile with the concentric electrodes and multiple channels on a high frequency monolithic quartz substrate without interference with the dual inverted mesa design. This high frequency multiple channels make the multiple gas detection feasible. Therefore, in this thesis the critical design parameters of this proposed design are analyzed and optimized through a comprehensive finite element analysis in COMSOL Multiphysics and analytical modelling. In addition, the interference between multiple QCM channels has been further eliminated. Furthermore, the fabrication procedure for the proposed high frequency QCM gas sensor array has been proposed and analyzed
Guiding Diamond Spin Qubit Growth with Computational Methods
The nitrogen vacancy (NV) center in diamond, a well-studied, optically active
spin defect, is the prototypical system in many state of the art quantum
sensing and communication applications. In addition to the enticing properties
intrinsic to the NV center, its diamond host's nuclear and electronic spin
baths can be leveraged as resources for quantum information, rather than
considered solely as sources of decoherence. However, current synthesis
approaches result in stochastic defect spin positions, reducing the
technology's potential for deterministic control and yield of NV-spin bath
systems, as well as scalability and integration with other technologies. Here,
we demonstrate the use of theoretical calculations of electronic central spin
decoherence as an integral part of an NV-spin bath synthesis workflow,
providing a path forward for the quantitative design of NV center-based quantum
sensing systems. We use computationally generated coherence data to
characterize the properties of single NV center qubits across relevant growth
parameters to find general trends in coherence time distributions dependent on
spin bath dimensionality and density. We then build a maximum likelihood
estimator with our theoretical model, enabling the characterization of a test
sample through NV T2* measurements. Finally, we explore the impact of
dimensionality on the yield of strongly coupled electron spin systems. The
methods presented herein are general and applicable to other qubit platforms
that can be appropriately simulated.Comment: 12 pages, 6 figure
First commissioning results of the multicusp ion source at MIT (MIST-1) for H2+
IsoDAR is an experiment under development to search for sterile neutrinos using the isotope Decay-At-Rest (DAR) production mechanism, where protons impinging on 9Be create neutrons which capture on 7Li which then beta-decays producing ve. As this will be an isotropic source of ve, the primary driver current must be large (10 mA cw) for IsoDAR to have sufficient statistics to be conclusive within 5 years of running. H2+ was chosen as primary ion to overcome some of the space-charge limitations during low energy beam transport and injection into a compact cyclotron. The H2+ will be stripped into protons before the target. At MIT, a multicusp ion source (MIST-1) was designed and built to produce a high intensity beam with a high H2+ fraction. MIST-1 is now operational at the Plasma Science and Fusion Center (PSFC) at MIT and under commissioning.National Science Foundation (U.S.). (Grant PHY-1505858)Bose Foundatio
Anomalous Purcell decay of strongly driven inhomogeneous emitters coupled to a cavity
We perform resonant fluorescence lifetime measurements on a
nanocavity-coupled erbium ensemble as a function of cavity-laser detuning and
pump power. Our measurements reveal an anomalous suppression of the ensemble
decay lifetime at zero cavity detuning and high pump fluence. We capture
qualitative aspects of this decay rate suppression using a Tavis-Cummings model
of non-interacting spins coupled to a common cavity.Comment: 4 figure
Quantum spin probe of single charge dynamics
Electronic defects in semiconductors form the basis for many emerging quantum
technologies. Understanding defect spin and charge dynamics in solid state
platforms is crucial to developing these building blocks, but many defect
centers are difficult to access at the single-particle level due to the lack of
sensitive readout techniques. A method for probing optically inactive spin
defects would reveal semiconductor physics at the atomic scale and advance the
study of new quantum systems. We exploit the intrinsic correlation between the
charge and spin states of defect centers to measure defect charge populations
and dynamics through the steady-state spin population, read-out at the
single-defect level with a nearby optically active qubit. We directly measure
ionization and charge relaxation of single dark defects in diamond, effects we
do not have access to with traditional coherence-based quantum sensing. These
spin resonance-based methods generalize to other solid state defect systems in
relevant materials.Comment: 8 pages, 4 figure
Tim-3 expression defines a novel population of dysfunctional T cells with highly elevated frequencies in progressive HIV-1 infection
Progressive loss of T cell functionality is a hallmark of chronic infection with human immunodeficiency virus 1 (HIV-1). We have identified a novel population of dysfunctional T cells marked by surface expression of the glycoprotein Tim-3. The frequency of this population was increased in HIV-1–infected individuals to a mean of 49.4 ± SD 12.9% of CD8+ T cells expressing Tim-3 in HIV-1–infected chronic progressors versus 28.5 ± 6.8% in HIV-1–uninfected individuals. Levels of Tim-3 expression on T cells from HIV-1–infected inviduals correlated positively with HIV-1 viral load and CD38 expression and inversely with CD4+ T cell count. In progressive HIV-1 infection, Tim-3 expression was up-regulated on HIV-1–specific CD8+ T cells. Tim-3–expressing T cells failed to produce cytokine or proliferate in response to antigen and exhibited impaired Stat5, Erk1/2, and p38 signaling. Blocking the Tim-3 signaling pathway restored proliferation and enhanced cytokine production in HIV-1–specific T cells. Thus, Tim-3 represents a novel target for the therapeutic reversal of HIV-1–associated T cell dysfunction
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