Jaggard, Dwight L

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Now showing 1 - 9 of 9
  • Publication
    Synchronization Recovery of Chaotic Wave Through an Imperfect Channel
    (2002-08-01) Yang, Xiaomin; Wu, Thomas X.; Jaggard, Dwight L
    We present a novel idea to recover synchronization using the genetic algorithm after a chaotic wave passes through an imperfect channel with constant attenuation and offset. The compensation block, which is added before the receiver, is used to compensate the distortion of the imperfect channel. A new concept, the synchronization mismatch is defined and used as the cost function in genetic algorithm to design the compensation block. The validity of this approach is suggested by numerical simulations.
  • Publication
    Canonical Sources and Duality in Chiral Media
    (1988-07-01) Jaggard, Dwight L; Engheta, Nader; Sun, Xiaoguang
    Chiral media are characterized by the constitutive relations D = εE + iXicB and H = B/µ + iXicE where Xic is the chirality admittance introduced to take into account macroscopic handedness or optical activity inherent in the media. In addition we define a chirality impedance and a dimensionless chirality factor to describe the wave properties of this medium. As known for some time, this medium supports the plane-wave propagation of circularly polarized waves of opposing handedness and differing wavenumbers. Here we examine the radiation of electromagnetic waves from a set of simple canonical arrays. This leads us to the notion of duality for chiral media which can be exhibited in a surprisingly simple form. We show that in the far field, both point and extended sources, whether electric or magnetic, radiate two electromagnetic eigenmodes which are of opposing handedness. We also demonstrate sources which access only one of the eigenmodes of the medium. Several applications of the results and array performance in chiral media are noted.
  • Publication
    Periodic Chiral Structures
    (1989-11-01) Jaggard, Dwight L; Engheta, Nader; Kowarz, Marek W.; Pelet, Philippe; Liu, John C.; Kim, Yunjin
    The electromagnetic properties of a structure that is both chiral and periodic are investigated using coupled-mode equations. The chirality is characterized by the constitutive relations D = εE + iXicB and H = iXicE+B/µ, where Xic is the chiral admittance. The periodicity is described by a sinusoidal perturbation of the permittivity, permeability and chiral admittance. The coupled-mode equations are derived from physical considerations. The coupled-mode equations are used to examine bandgap structure and reflected and transmitted fields. Chirality is observed predominantly in transmission while periodicity is present in both reflection and transmission.
  • Publication
    Knots, Symmetry, and Scattering
    (2001-09-01) Manuar, Omar; Jaggard, Dwight L
    We investigate the physics underlying the scattering of circularly polarized plane waves from a toroidal knot and related unknot. We find that backscattering along the axis of rotational symmetry from trefoil knots is cross polarized; copolarized backscatter is in the numerical noise. In contrast, untrefoils give appreciable backscattering cross sections for both polarizations. We also study an intermediate class of structures: morphs, which provides a geometrical bridge between trefoil and untrefoil. We pursue physical insight for the depolarization associated with asymmetric objects, tracing the connection from the induced charge distribution, to the induced moments, to the polarization of the backscattered field.
  • Publication
    SPAR - Positive Intervention Application Plan for Ashoka University
    (2017-04-01) Griffin, Erin; Jaggard, Dwight; Singh, Glory; Turak, Jessica
    Ashoka University, a distinguished liberal arts university that is the intellectual home to over 900 hundred undergraduate and graduate students in Sonepat, India. We present here a program to enhance well-being based on the fundamentals of positive psychology. The program can start with a pilot and then be scaled using either trained professionals or trained peer counselors. The components of the program include strengths, positive relationships, attention and resilience thus forming the acronym SPAR. We have designed the program to take place in four 90-minute sessions ideal for the Young India Fellowship Fellows schedule of five-week semesters. It is equally applicable to undergraduates and could also be rolled out for faculty and staff if desired. We include a slide deck that is ready to use for the first session.
  • Publication
    Simultaneous fluorometry and phosphorometry of Langendorff perfused rat heart: ex vivo animal studies
    (2006-10-15) Ranji, Mahsa; Jaggard, Dwight; Apreleva, Sofia; Vinogradov, Sergei; Chance, Britton
    Fluorescence imaging of intrinsic fluorophores of tissue is a powerful method to assess metabolic changes at the cellular and intracellular levels. At the same time, exogenous phosphorescent probes can be used to accurately measure intravascular tissue oxygenation. Heart failure is the leading cause of death in America. A rat heart can potentially model the human heart to study failures or other abnormalities optically. We report simultaneous fluorescence and phosphorescence measurements performed on a rat heart. We have used two different optical systems to acquire fluorescence signals of flavoprotein and nicotinamide adenine dinucleotide—the two intrinsic fluorophores of mitochondria—and the phosphorescence signal of an intravascular oxygen probe to extract intracellular and intravascular metabolism loads, respectively.
  • Publication
    Fluorescence spectroscopy and imaging of myocardial apoptosis
    (2006-12-01) Ranji, Mahsa; Gorman, Joseph H; Kanemoto, Shinya; Gorman, Robert C; Matsubara, Muneaki; Jaggard, Dwight; Grosso, Michael A; Chance, Britton
    Fluorometry is used to detect intrinsic flavoprotein (FP) and nicotinamide adenine dinucleotide NADH signals in an open-chest rabbit model of myocardial ischemia-reperfusion injury. Myocyte apoptosis has been shown clinically to contribute to infarct size following reperfusion of ischemic myocardium. A noninvasive means of assessing apoptosis in this setting would aid in the treatment of subsequent ventricular remodeling. We show that in vivo fluorometry can be useful in apoptosis detection in open-chest surgeries. Specific changes in myocardial redox states have been shown to indicate the presence of apoptosis. Two main mitochondrial intrinsic fluorophores, NADH and FP signals, were measured during normoxia, ischemia, and reperfusion experimental protocol. Ischemia was induced by occlusion of the largest branch of the circumflex coronary artery and fluorescence signals are collected by applying two different fluorescence techniques: in vivo fluorometry and postmortem cryoimaging. The first technique was employed to detect FP and NADH signals in vivo and the latter technique uses freeze trapping and lowtemperature fluorescence imaging. The heart is snap frozen while still in the chest cavity to make a "snapshot" of the metabolic state of the tissue. After freezing, the ischemic area and its surrounding border zone were excised and the sample was embedded in a frozen buffer for cryoscanning. These two data sets, in vivo fluorometry and low temperature redox scanning, show consistent extreme oxidation of the mitochondrial redox states (higher redox ratio) suggesting the initiation of apoptosis following reperfusion. This represents the first attempt to assess myocyte apoptosis in the beating heart.
  • Publication
    Quantifying Acute Myocardial Injury Using Ratiometric Fluorometry
    (2009-05-01) Hinmon, Robin H; Jaggard, Dwight L; Ranji, Mahsa; Chance, Britton; Matsubara, Muneaki; Gorman, Robert C; Leshnower, Bradley G; Gorman, Joseph H
    Early reperfusion is the best therapy for myocardial infarction (MI). Effectiveness, however, varies significantly between patients and has implications for long-term prognosis and treatment. A technique to assess the extent of myocardial salvage after reperfusion therapy would allow for high-risk patients to be identified in the early post-MI period. Mitochondrial dysfunction is associated with cell death following myocardial reperfusion and can be quantified by fluorometry. Therefore, we hypothesized that variations in the fluorescence of mitochondrial nicotinamide adenine dinucleotide (NADH) and flavoprotein (FP) can be used acutely to predict the degree of myocardial injury. Thirteen rabbits had coronary occlusion for 30 min followed by 3 h of reperfusion. To produce a spectrum of infarct sizes, six animals were infused cyclosporine A prior to ischemia. Using a specially designed fluorometric probe, NADH and FP fluorescence were measured in the ischemic area. Changes in NADH and FP fluorescence, as early as 15 min after reperfusion, correlated with postmortem assessment infarct size (r=0.695, p<0.01). This correlation strengthened with time (r=0.827, p<0.01 after 180 min). Clinical application of catheter-based myocardial fluorometry may provide a minimally invasive technique for assessing the early response to reperfusion therapy.
  • Publication
    Electromagnetic Waves in Faraday Chiral Media
    (1992-04-01) Engheta, Nader; Jaggard, Dwight; Kowarz, Marek W.
    Plane wave propagation in two kinds of Faraday chiral media, where Faraday rotation is combined with optical activity, is studied to examine methods of controlling chirality. The two types of media studied are magnetically biased chiroplasmas and chiroferrites. For propagation along the biasing magnetic field, four wavenumbers and two wave impedances are found which are dependent on the strength of the biasing field. Dispersion diagrams for the chiroplasma case are plotted. Propagation at the plasma frequency of the chiroplasma is also investigated.