Alpha antagonists and intraoperative floppy iris syndrome: A spectrum

Sharif A Issa, Omar H Hadid, Oliver Baylis, Margaret DayanDepartment of Ophthalmology, Royal Victoria Infirmary, Newcastle upon Tyne, UKBackground: To determine occurrence of features of intraoperative floppy iris syndrome (IFIS) during cataract surgery in patients taking systemic alpha-antagonists (AA).Methods: We prospectively studied patients on AA and who underwent phacoemulsification. The following were recorded: pupil diameter preoperatively, iris flaccidity, iris prolapse and peroperative miosis.Results: We studied 40 eyes of 31 subjects. Mean age was 78 years. Overall, 14 eyes (13 patients) showed signs of IFIS: 9/13 (69%) eyes of patients on tamsulosin, 1/18 (6%) eyes in the doxazosin group, 2/2 prazosin patients, 1/4 eyes in the indoramin group, and 1/2 eyes in two patients on a combination of doxazosin and tamsulosin. Most cases (92%) had only one or two signs of IFIS. Bilateral cataract surgery was undertaken in 9 patients but only one patient (on tamsulosin) had features of IFIS in both eyes, while 4 patients (2 on tamsulosin and 2 on other AA) showed signs of IFIS in one eye only, and 4 patients did not show IFIS in either eye.Conclusion: Most AA were associated with IFIS, but it tends to present as a spectrum of signs rather than full triad originally described. Tamsulosin was most likely to be associated with IFIS; however, its intake does not necessarily mean that IFIS will occur. For patients on AA, the behavior of the iris intraoperatively in one eye is a poor predictor of the other eye. Surgeons should anticipate the occurrence of IFIS in any patient on AA.Keywords: alpha blocker, alpha antagonist, cataract surgery, intraoperative floppy iris syndrome, tamsulosin

Dairy heifers naturally exposed to Fasciola hepatica develop a type-2 immune response and concomitant suppression of leukocyte proliferation

Fasciola hepatica is a parasitic trematode of global importance in livestock. Control strategies reliant on anthelmintics are unsustainable due to the emergence of drug resistance. Vaccines are under development, but efficacy is variable. Evidence from experimental infection suggest vaccine efficacy may be affected by parasite-induced immunomodulation. Little is known about the immune response to F. hepatica following natural exposure. Hence we analysed the immune responses over time in calves naturally exposed to F. hepatica infection.Cohorts of replacement dairy heifer calves (n=42) with no prior exposure to F. hepatica, on three commercial dairy farms, were sampled over the course of a grazing season. Exposure was determined through F. hepatica-specific serum antibody ELISA and fluke egg counts. Concurrent changes in peripheral blood leukocyte sub-populations, lymphocyte proliferation and cytokine responses were measured. Relationships between fluke infection and immune responses were analysed using multivariable linear mixed effect models.All calves from one farm showed evidence of exposure, whilst cohorts from the remaining two farms remained negative over the grazing season. A type-2 immune response was associated with exposure, with increased interleukin (IL)-4 production, IL-5 transcription and eosinophilia. Suppression of parasite-specific PBMC proliferation was evident; while decreased mitogen stimulated IFN-γ production suggested immunomodulation, which was not restricted to parasite-specific responses. Our findings show that the global immune response is modulated towards a non-proliferative type-2 state following natural challenge with F. hepatica This has implications for vaccination programmes in terms of the timing of administration of vaccination programmes, and for host susceptibility to co-infecting pathogens

On the Solutions of the Lorentz-Dirac Equation

We discuss the unstable character of the solutions of the Lorentz-Dirac equation and stress the need of methods like order reduction to derive a physically acceptable equation of motion. The discussion is illustrated with the paradigmatic example of the non-relativistic harmonic oscillator with radiation reaction. We also illustrate removal of the noncasual pre-acceleration with the introduction of a small correction in the Lorentz-Dirac equation.Comment: 4 eps figs. to be published in GR

Hamilton's Turns for the Lorentz Group

Hamilton in the course of his studies on quaternions came up with an elegant geometric picture for the group SU(2). In this picture the group elements are represented by ``turns'', which are equivalence classes of directed great circle arcs on the unit sphere $S^2$, in such a manner that the rule for composition of group elements takes the form of the familiar parallelogram law for the Euclidean translation group. It is only recently that this construction has been generalized to the simplest noncompact group $SU(1,1) = Sp(2, R) = SL(2,R)$, the double cover of SO(2,1). The present work develops a theory of turns for $SL(2,C)$, the double and universal cover of SO(3,1) and $SO(3,C)$, rendering a geometric representation in the spirit of Hamilton available for all low dimensional semisimple Lie groups of interest in physics. The geometric construction is illustrated through application to polar decomposition, and to the composition of Lorentz boosts and the resulting Wigner or Thomas rotation.Comment: 13 pages, Late

Electromagnetic inertia, reactive energy, and energy flow velocity

In a recent paper titled "Coherent electromagnetic wavelets and their twisting null congruences," I defined the local inertia density (I), reactive energy density (R), and energy flow velocity (v) of an electromagnetic field. These are the field equivalents of the mass, rest energy, and velocity of a relativistic particle. Thus R and I are Lorentz-invariant and |v|<=c, with equality if and only if R=0. The exceptional fields with |v|=c were called "coherent" because their energy moves in complete harmony with the field, leaving no inertia or reactive energy behind. Generic electromagnetic fields become coherent only in the far zone. Elsewhere, their energy flows at speeds |v|<c. The purpose of this paper is to confirm and clarify this statement by studying the local energy flow in several common systems: a time-harmonic electric dipole field, a time-dependent electric dipole field, and a standing plane wave. For these fields, the energy current (Poynting vector) is too weak to carry away all of the energy, thus leaving reactive energy in its wake. For the time-dependent dipole field, we find that the energy can flow both transversally and inwards, back to the source. Neither of these phenomena show up in the usual computation of the energy transport velocity which considers only averages over one period in the time-harmonic case.Comment: 20 pages, 7 figure

Revisiting special relativity: A natural algebraic alternative to Minkowski spacetime

Minkowski famously introduced the concept of a space-time continuum in 1908, merging the three dimensions of space with an imaginary time dimension $i c t$, with the unit imaginary producing the correct spacetime distance $x^2 - c^2 t^2$, and the results of Einstein's then recently developed theory of special relativity, thus providing an explanation for Einstein's theory in terms of the structure of space and time. As an alternative to a planar Minkowski space-time of two space dimensions and one time dimension, we replace the unit imaginary $i = \sqrt{-1}$, with the Clifford bivector $\iota = e_1 e_2$ for the plane that also squares to minus one, but which can be included without the addition of an extra dimension, as it is an integral part of the real Cartesian plane with the orthonormal basis $e_1$ and $e_2$. We find that with this model of planar spacetime, using a two-dimensional Clifford multivector, the spacetime metric and the Lorentz transformations follow immediately as properties of the algebra. This also leads to momentum and energy being represented as components of a multivector and we give a new efficient derivation of Compton's scattering formula, and a simple formulation of Dirac's and Maxwell's equations. Based on the mathematical structure of the multivector, we produce a semi-classical model of massive particles, which can then be viewed as the origin of the Minkowski spacetime structure and thus a deeper explanation for relativistic effects. We also find a new perspective on the nature of time, which is now given a precise mathematical definition as the bivector of the plane.Comment: 29 pages, 2 figure

Standardization of Nucleic Acid Tests:The Approach of the World Health Organization

The first World Health Organization (WHO) international standards (ISs) for nucleic acid amplification techniques were established two decades ago, with the initial focus on blood screening for three major viral targets, i.e., hepatitis C virus, hepatitis B virus, and human immunodeficiency virus 1. These reference materials have subsequently found utility in the diagnosis and monitoring of a wide range of infectious diseases in clinical microbiology laboratories worldwide. WHO collaborating centers develop ISs and coordinate international studies for their evaluation. The WHO Expert Committee on Biological Standardization is responsible for the endorsement of new standardization projects and the establishment of new and replacement ISs. Potencies of ISs are defined in international units (IU); the reporting in IU for assays calibrated with an IS (or secondary standards traceable to the IS) facilitates comparability of results for different assays and determination of assay parameters such as analytical sensitivities