Age-related differences in self-harm presentations and subsequent management of adolescents and young adults at the emergency department

Background Characteristics of self-harm differ across ages, but there is little work identifying age-related differences in younger people. Young people entering adolescence face emotionally and developmentally different challenges to those entering adulthood. This study investigates how Emergency Department (ED) presentations and management of self-harm differ through adolescence and early adulthood. Methods 3782 consecutive self-harm episodes involving 2559 people aged 12–25 years were identified from an existing database of Leeds ED attendances from 2004–2007. Odds ratios for each of four age bands were compared to the remaining young people. Results The female to male ratio was 6.3:1 at 12–14 years old, decreasing with successive age groups to 1.2:1 at 22–25 years old. Self-poisoning was commoner in those under 18 years old. 18–25 year olds were more likely to self-poison with prescribed medications, mixed overdoses, alcohol or recreational drugs. 18–25 year olds more often required medical treatment for the effects of the self-harm. 12–14 year olds were more often seen urgently by ED medical staff and offered high intensity mental health aftercare. Repetition of self-harm was commonest in 12–14 year olds, although multiple repetition of self-harm was commonest in 22–25 year olds. Limitations Data were not collected on whether the aftercare offered was received. The study sample included hospital attenders only. Conclusions The large excess of females over males in young people’s self-harm is only true at the younger age range. Older adolescents present with more severe acts of self-harm, yet receive the lowest intensity of assessment and after care

Photon position operators and localized bases

We extend a procedure for construction of the photon position operators with transverse eigenvectors and commuting components [Phys. Rev. A 59, 954 (1999)] to body rotations described by three Euler angles. The axial angle can be made a function of the two polar angles, and different choices of the functional dependence are analogous to different gauges of a magnetic field. Symmetries broken by a choice of gauge are re-established by transformations within the gauge group. The approach allows several previous proposals to be related. Because of the coupling of the photon momentum and spin, our position operator, like that proposed by Pryce, is a matrix that does not commute with the spin operator. Unlike the Pryce operator, however, our operator has commuting components, but the commutators of these components with the total angular momentum require an extra term to rotate the matrices for each vector component around the momentum direction. Several proofs of the nonexistence of a photon position operator with commuting components are based on overly restrictive premises that do not apply here

Photon location in spacetime

The NewtonWigner basis of orthonormal localized states is generalized to orthonormal and relativistic biorthonormal bases on an arbitrary hyperplane in spacetime. This covariant formalism is applied to the measurement of photon location using a hypothetical 3D array with pixels throughout space turned on at a fixed time and a timelike 2D photon counting array detector with good time resolution. A moving observer will see these detector arrays as rotated in spacetime but the spacelike and timelike experiments remain distinct.Comment: Equations (18) to (21) and the relevant text deleted due to an error in (20). This is no effect on the conclusions of the pape

Monodromy-data parameterization of spaces of local solutions of integrable reductions of Einstein's field equations

For the fields depending on two of the four space-time coordinates only, the spaces of local solutions of various integrable reductions of Einstein's field equations are shown to be the subspaces of the spaces of local solutions of the ``null-curvature'' equations constricted by a requirement of a universal (i.e. solution independent) structures of the canonical Jordan forms of the unknown matrix variables. These spaces of solutions of the ``null-curvature'' equations can be parametrized by a finite sets of free functional parameters -- arbitrary holomorphic (in some local domains) functions of the spectral parameter which can be interpreted as the monodromy data on the spectral plane of the fundamental solutions of associated linear systems. Direct and inverse problems of such mapping (``monodromy transform''), i.e. the problem of finding of the monodromy data for any local solution of the ``null-curvature'' equations with given canonical forms, as well as the existence and uniqueness of such solution for arbitrarily chosen monodromy data are shown to be solvable unambiguously. The linear singular integral equations solving the inverse problems and the explicit forms of the monodromy data corresponding to the spaces of solutions of the symmetry reduced Einstein's field equations are derived.Comment: LaTeX, 33 pages, 1 figure. Typos, language and reference correction

Quantum field theory and classical optics: determining the fine structure constant

The properties of the vacuum are described by quantum physics including the response to external fields such as electromagnetic radiation. Of the two parameters that govern the details of the electromagnetic field dynamics in vacuum, one is fixed by the requirement of Lorentz invariance $c= 1/\sqrt{\varepsilon_{0} \mu_{0}}$. The other one, $Z_{0}= \sqrt{\mu_{0}/\varepsilon_{0}} = 1/(c\varepsilon_{0})$ and its relation to the quantum vacuum, is discussed in this contribution. Deriving $\varepsilon_{0}$ from the properties of the quantum vacuum implies the derivation of the fine structure constant.Comment: 3 pages. Invited contribution to MPLP 2017 Novosibirsk "Modern Problems in Laser Physics". Comments welcome

Photon correlations in positron annihilation

The two-photon positron annihilation density matrix is found to separate into a diagonal center of energy factor implying maximally entangled momenta, and a relative factor describing decay. For unknown positron injection time, the distribution of the difference in photon arrival times is a double exponential at the para-Ps decay rate, consistent with experiment (V. D. Irby, Meas. Sci. Technol. 15, 1799 (2004)).Comment: Accepted for publication in Phys. Rev.