Electromagnetic Radiation in the Presence of Moving Simple Media

The radiation pattern of an arbitrary source immersed in a moving simple medium is calculated by deducing the differential equation for the potential 4‐vector in the rest frame of the source and then solving the equation in terms of a Green's function. As an illustrative example, the case where the source is an oscillating dipole is worked out in detail

Radiation resistance and irreversible power of antennas in gyroelectric media

In recent years, many investigators have been working on the problem of calculating the radiation resistance of a dipole antenna immersed in an anisotropic medium [1]. The central difficulty of their method of calculation is that it yields an infinite value for the radiation resistance. They hare attributed this infinity to the infinitesimal size of the source, and have suggested that if the source were of finite spatial extent the difficulty would not arise. It is our contention that the difficulty is of a more basic nature and is not due to the size of the source but to the method of calculation. The purpose of this letter is to show that if the radiation resistance is calculated with proper conformity to the thermodynamical laws of reversibility and irreversibility, the value of the radiation resistance will turn out to be finite. Clearly, radiation resistance is on the same footing as ordinary circuit resistance in the sense that they both are measures of irreversible power, and hence in calculating radiation resistance it is necessary that only the irreversible part of the power be used. Accordingly, we shall construct an expression for the irreversible part of the power emitted by a source, and show that the expression so constructed is finite and hence leads to a finite value for the radiation resistance. To construct the required expression, we recall that in the case of an accelerating point electron in vacuum, the combination of half the retarded minus half the advanced field is free from singularity [2] and corresponds to the irreversible power radiated by the electron [3]. We shall extend this idea of taking a combination field to the case of a monochro matic source Re(Je^(iWt)) radiating into a lossless anisotropic medium

Islet Assessment for Transplantation

Author Manuscript: 2010 December 1.Purpose of review: There is a critical need for meaningful viability and potency assays that characterize islet preparations for release prior to clinical islet cell transplantation (ICT). Development, testing, and validation of such assays have been the subject of intense investigation for the past decade. These efforts are reviewed, highlighting the most recent results while focusing on the most promising assays. Recent Findings: Assays based on membrane integrity do not reflect true viability when applied to either intact islets or dispersed islet cells. Assays requiring disaggregation of intact islets into individual cells for assessment introduce additional problems of cell damage and loss. Assays evaluating mitochondrial function, specifically mitochondrial membrane potential, bioenergetic status, and cellular oxygen consumption rate (OCR), especially when conducted with intact islets, appear most promising in evaluating their quality prior to ICT. Prospective, quantitative assays based on measurements of OCR with intact islets have been developed, validated and their results correlated with transplant outcomes in the diabetic nude mouse bioassay. Conclusion: More sensitive and reliable islet viability and potency tests have been recently developed and tested. Those evaluating mitochondrial function are most promising, correlate with transplant outcomes in mice, and are currently being evaluated in the clinical setting.National Center for Research Resources (U.S.) (Grant)National Institutes of Health (U.S.) (Grant U42 RR 016598–01)National Institutes of Health (U.S.) (Grant RO1-DK063108–01A1)Iacocca FoundationSchott FoundationCarol Olson Memorial Diabetes Research Fun

Antenna radiation in a moving dispersive medium

The general problem of calculating the radiation field of an antenna immersed in a moving dispersive medium is formulated as an algebraic equation in wave-vector frequency space for the potential 4-vector in the rest frame of the antenna, and is solved in terms of a Green's function having the form of a one-dimensional integral. The special case where the moving medium is a homogeneous ionized gas (plasma) and the antenna is an oscillating dipole is studied in detail. It is found that the far-zone field is not transverse and the Poynting vector is not purely radial

The Incoherent Scattering of Electromagnetic Waves by Free Electrons

In this paper the incoherent scattering of an electromagnetic wave by free electrons is examined theoretically. Under the assumption that the electrons have a Maxwellian velocity distribution, the scattered power and its frequency spectrum are calculated. The applicability of these results to ionospheric and laboratory plasmas is discussed

Dynamical Theory of Artificial Optical Magnetism Produced by Rings of Plasmonic Nanoparticles

We present a detailed analytical theory for the plasmonic nanoring configuration first proposed in [A. Alu, A. Salandrino, N. Engheta, Opt. Expr. 14, 1557 (2006)], which is shown to provide negative magnetic permeability and negative index of refraction at infrared and optical frequencies. We show analytically how the nanoring configuration may provide superior performance when compared to some other solutions for optical negative index materials, offering a more 'pure' magnetic response at these high frequencies, which is necessary for lowering the effects of radiation losses and absorption. Sensitivity to losses and the bandwidth of operation of this magnetic inclusion are also investigated in details and compared with other available setups.Comment: 34 pages, 3 figure

Is there a relationship between periodontal conditions and number of medications among the elderly?

Objective: To investigate possible correlations of clinical attachment level and pocket depth with number of medications in elderly individuals.Methods: Intra-oral examinations for 139 patients visiting Tufts dental clinic were done. Periodontal assessments were performed with a manual UNC-15 periodontal probe to measure probing depth (PD) and clinical attachment level (CAL) at 6 sites. Complete lists of patients’ medications were obtained during the examinations. Statistical analysis involved Kruskal-Wallis, chi square and multivariate logistic regression analyses.Results: Age and health status attained statistical significance (p< 0.05), in contingency table analysis with number of medications. Number of medications had an effect on CAL: increased attachment loss was observed when 4 or more medications were being taken by the patient. Number of medications did not have any effect on periodontal PD. In multivariate logistic regression analysis, 6 or more medications had a higher risk of attachment loss (>3mm) when compared to the no-medication group, in crude OR (1.20, 95% CI:0.22-6.64), and age adjusted (OR=1.16, 95% CI:0.21-6.45), but not with the multivariate model (OR=0.71, 95% CI:0.11-4.39).Conclusion: CAL seems to be more sensitive to the number of medications taken, when compared to PD. However, it is not possible to discriminate at exactly what number of drug combinations the breakdown in CAL will happen. We need to do further analysis, including more subjects, to understand the possible synergistic mechanisms for different drug and periodontal responses.Keywords: periodontal disease, medications, elderly, clinical attachment level, probing dept

Postnatal β2 adrenergic treatment improves insulin sensitivity in lambs with IUGR but not persistent defects in pancreatic islets or skeletal muscle

Placental insufficiency causes intrauterine growth restriction (IUGR) and disturbances in glucose homeostasis with associated β adrenergic receptor (ADRβ) desensitization. Our objectives were to measure insulin-sensitive glucose metabolism in neonatal lambs with IUGR and to determine whether daily treatment with ADRβ2 agonist and ADRβ1/β3 antagonists for 1 month normalizes their glucose metabolism. Growth, glucose-stimulated insulin secretion (GSIS) and glucose utilization rates (GURs) were measured in control lambs, IUGR lambs and IUGR lambs treated with adrenergic receptor modifiers: clenbuterol atenolol and SR59230A (IUGR-AR). In IUGR lambs, islet insulin content and GSIS were less than in controls; however, insulin sensitivity and whole-bodyGUR were not different from controls.Of importance, ADRβ2 stimulation with β1/β3 inhibition increases both insulin sensitivity and whole-body glucose utilization in IUGR lambs. In IUGR and IUGR-AR lambs, hindlimb GURs were greater but fractional glucose oxidation rates and ex vivo skeletal muscle glucose oxidation rates were lower than controls. Glucose transporter 4 (GLUT4) was lower in IUGR and IUGR-AR skeletal muscle than in controls but GLUT1 was greater in IUGR-AR. ADRβ2, insulin receptor, glycogen content and citrate synthase activity were similar among groups. In IUGR and IUGR-AR lambs heart rates were greater, which was independent of cardiac ADRβ1 activation. We conclude that targeted ADRβ2 stimulation improved whole-body insulin sensitivity but minimally affected defects in GSIS and skeletal muscle glucose oxidation. We show that risk factors for developing diabetes are independent of postnatal catch-up growth in IUGR lambs as early as 1 month of age and are inherent to the islets and myocytes