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Posttransplant cyclophosphamide, sirolimus and mycophenolate mofetil (PTCy/siro/MMF) constitutes an innovative and well-tolerated acute graft-versus-host disease (aGVHD) prophylaxis after allogeneic stem cell transplantation (allo-HSCT), but risk factors for aGVHD incidence and therapy failure in this setting are scarce. This study prospectively registered all consecutive adult patients with hematologic malignancies who received a myeloablative allo-HSCT using PTCy/siro/MMF prophylaxis at our institution between 2017 and 2023. A total of 385 patients were included, of whom 44%, 34% and 22% were transplanted from matched sibiling, matched unrelated and haploidentical donors, respectively. The 180-day cumulative incidence of aGVHD was 21% (95% confidence interval [CI] 17–25%) for grade II–IV and 11% (95% CI 8–14%) grade III–IV aGVHD. The use of haploidentical donors was associated with an increased risk of severe aGVHD. Among 75 patients receiving first-line systemic corticosteroids, 49% achieved a sustained complete response, while 23% and 24% developed steroid-dependent (SD-aGVHD) and steroid-refractory aGVHD (SR-aGVHD), respectively. SR-aGVHD was associated with worse salvage treatment response and overall survival compared to SD-aGVHD. The 1-year cumulative incidence of aGVHD-related mortality was 5.4% (95% CI, 3.3–8.1). Risk factors for aGVHD-related mortality included haploidentical donors, older donors, diagnosis of myeldysplastic neoplasms, and grade IV aGVHD. This study confirms a low incidence aGVHD with PTCy/siro/MMF prophylaxis. SR-aGVHD showed poorer response to salvage therapies and worse survival, while haploidentical donors and older donor age were negative predictors for aGVHD-related deaths.

IT'S HARD to believe that voters have rejected the referendum for cannabis legalisation but unanimously voted in favour of the End of Life Choice Act. Were the people who voted [...]

Introduction

Aims and methodThis work builds on a survey first done in 1999 to understand how old age psychiatry teaching is embedded in undergraduate medical schools in the UK and Ireland and the influence of academic old age psychiatrists on teaching processes. We invited deans of 31 medical schools in the UK and Ireland in 2015 to complete an online survey to reassess the situation 16 years later.ResultsResponse rate was 74%. As found in the original survey, there was variation across medical schools in how old age psychiatry is taught. Half of schools stated there was not enough space in the curriculum dedicated to old age psychiatry, and not all medical school curricula offered a clinical attachment. Medical schools that involved academic old age psychiatrists in teaching (59%) showed a greater diversity of teaching methods.Clinical implicationsThere is a need to recognise the importance of old age psychiatry teaching, with the consensus of opinion continuing to be that more curriculum space needs to be given to old age psychiatry. To achieve this we advocate increasing the number of old age psychiatrists with teaching roles, as relying on academics to teach and lead on curriculum development is challenging given their greater research pressures.

AbstractThe availability of ever stronger, laser-generated electromagnetic fields underpins continuing progress in the study and application of nonlinear phenomena in basic physical systems, ranging from molecules and atoms to relativistic plasmas and quantum electrodynamics. This raises the question: how far will we be able to go with future lasers? One exciting prospect is the attainment of field strengths approaching the Schwinger critical field ${E}_{\mathrm{cr}}$ in the laboratory frame, such that the field invariant ${E}^2-{c}^2{B}^2>{E}_{\mathrm{cr}}^2$ is reached. The feasibility of doing so has been questioned, on the basis that cascade generation of dense electron–positron plasma would inevitably lead to absorption or screening of the incident light. Here we discuss the potential for future lasers to overcome such obstacles, by combining the concept of multiple colliding laser pulses with that of frequency upshifting via a tailored laser–plasma interaction. This compresses the electromagnetic field energy into a region of nanometre size and attosecond duration, which increases the field magnitude at fixed power but also suppresses pair cascades. Our results indicate that laser facilities with peak power of tens of PW could be capable of reaching ${E}_{\mathrm{cr}}$ . Such a scenario opens up prospects for the experimental investigation of phenomena previously considered to occur only in the most extreme environments in the universe.

•Off-line extracorporeal electrophoresis (ECP) is a safe and effective alternative for steroid refractory and dependent graft-versus-host disease.•Our study validates a treatment schedule previously proposed by independent investigators.•Further investigation is required to identify ECP-specific predictive factors for response.

We study nonperturbative pair production in electric fields with lightlike inhomogeneities, using complex worldline instantons. We show that the instanton contribution to the pair production probability is a complex contour integral over the instanton itself, and that pair production in the considered fields can be recast in terms of Cauchy's residue theorem. The instantons contribute residues from the poles they circulate (i.e. give local contributions), and the invariance of complex integrals under contour deformation manifests in the instanton contributions as invariance under a set of generalized, complex, reparametrizations. [ABSTRACT FROM AUTHOR]

We test current numerical implementations of laser-matter interactions by comparison with exact analytical results. Focusing on photon emission processes, it is found that the numerics accurately reproduce analytical emission spectra in all considered regimes, except for the harmonic structures often singled out as the most significant high-intensity (multiphoton) effects. We find that this discrepancy originates in the use of the locally constant field approximation. [ABSTRACT FROM AUTHOR]

The production of electron-positron pairs from light is a famous prediction of quantum electrodynamics. Yet it is often emphasized that the number of produced pairs has no physical meaning until the driving electromagnetic fields are switched off, as otherwise its definition is basis dependent. The common adiabatic definition, in particular, can predict the "creation" of a number of pairs orders of magnitude larger than the final yield. We show here, by clarifying exactly what is being counted, that the adiabatic number of pairs has an unambiguous and physical interpretation. As a result, and perhaps contrary to expectation, the large numbers of pairs seen at nonasymptotic times become, in principle, physically accessible. [ABSTRACT FROM AUTHOR]

We introduce a nonperturbative, first-principles numerical approach for solving time-dependent problems in quantum field theory, using light-front quantization. As a first application we consider QED in a strong background field, and the process of nonlinear Compton scattering in which an electron is excited by the background and emits a photon. We track the evolution of the quantum state as a function of time. Observables, such as the invariant mass of the electron-photon pair, are first checked against results from perturbation theory, for suitable parameters. We then proceed to a test case in the strong background field regime and discuss the various nonperturbative effects revealed by the approach. [ABSTRACT FROM AUTHOR]

We derive dynamical, real time radiation reaction effects from lightfront QED. Combining the Hamiltonian formalism with a plane wave background field, the calculation is performed in the Furry picture for which the background is treated exactly while interactions between quantum fields are treated in perturbation theory as normal. We work to a fixed order in perturbation theory, but 'no other approximation is made. The literature contains many proposals for the correct classical equation . describing a radiating particle; we take the classical limit of our results and identify which equations are consistent with QED. [ABSTRACT FROM AUTHOR]

We consider two aspects of scattering in strong plane-wave backgrounds. First, we show that the infrared divergences in elastic scattering depend on the structure of the background, but can be removed using the usual Bloch-Nordsieck approach. Second, we analyze the infinite series of shifted-mass-shell poles in the particle (Volkov) propagator using lightfront quantization. The complete series of poles is shown to describe a single, on-shell, propagating particle. [ABSTRACT FROM AUTHOR]

We discuss the theory and phenomenology of pair annihilation, within an ultrashort laser pulse, to a single photon. The signature of this process is the unidirectional emission of single photons with a fixed energy. We show that the cross section is significantly larger than for two-photon pair annihilation in vacuum, with x-ray free-electron laser parameters admitting a much clearer signal than optical beams. [ABSTRACT FROM AUTHOR]

Current high-intensity laser sources offer a multitude of research, experiment and application possibilities, ranging from e.g. ionisation studies of atomic and molecular systems to particle acceleration for medical purposes. Planned upgrades of existing laser sources will further increase the deliverable intensities and make certain lowintensity (as compared to the Schwinger field) tests of quantum electrodynamics viable. Moreover, secondary sources of radiation, and planned future facilities, offer several-orders-of-magnitude increases in intensities. Thus, it is highly relevant to ask what kind of physics that may be probed using future light sources.

We investigate strong field vacuum effects using a phase-space approach based on the Wigner formalism. We calculate the Wigner function in a strong null-field background exactly, using lightfront field theory. The Wigner function exhibits the distinct features of strong field QED: in particular, we identify the effective mass in a laser pulse, compare it to the well-known mass shift in a periodic plane wave and identify signals of multiphoton absorption and emission. Finally, we show how to extend our results to describe vacuum pair production in colliding laser pulses. [ABSTRACT FROM AUTHOR]

We discuss various limits which transform configuration space into phase space, with emphasis on those related to lightfront field theory, and show that they are unified by spectral flow. Examples include quantising in ‘almost lightfront’ coordinates and the appearance of lightlike noncommutativity from a strong background laser field. We compare this with the limit of a strong magnetic field, and investigate the role played by lightfront zero modes. [Copyright &y& Elsevier]

We consider the scattering of probe particles on an ultraboosted beam of charge, in the case that the fields of the beam are strong and must be treated nonperturbatively. We show that the fields of the ultraboosted beam act as stochastic plane waves--scattering amplitudes (of elastic scattering, nonlinear Compton and nonlinear Breit-Wheeler) are obtained without approximation by averaging plane wave scattering amplitudes over all possible plane wave parameters. The relevant plane waves are ultrashort and, as such, scattering on ultraboosted beams does not exhibit the conjectured strong-field behavior of QED based on the locally constant field approximation. [ABSTRACT FROM AUTHOR]

Scattering processes in laser backgrounds are degenerate to the emission of unobservable photons collinear with the laser. We identify processes and observables for which such degeneracies factorize and exponentiate, obtaining the leading-order intensity dependence of these inclusive observables at high laser intensity, correct to all orders in the fine-structure constant (all loops, all emissions). The results show an exponential intensity dependence distinct from that predicted by the Narozhny-Ritus conjecture on the high-intensity behavior of quantum electrodynamics in strong fields. [ABSTRACT FROM AUTHOR]

Radiative and nonradiative electron spin-flip probabilities are analyzed in both plane wave and focused laser backgrounds. We provide a simple and physically transparent description of spin dynamics in plane waves, and demonstrate that there exists a kinematic regime in which the usual leading-order perturbative hierarchy of quantum electrodynamics is reversed, and nonradiative loop effects dominate over radiative tree-level spin flips. We show that while this loop dominance becomes suppressed in focused laser pulses due to a high sensitivity to field geometry, there is nevertheless a regime in which, in principle, loop effects on spin transitions can be discerned. [ABSTRACT FROM AUTHOR]

The framework of "time-dependent basis light-front quantization" (tBLFQ) offers a nonperturbative approach to scattering problems in external fields, based on Fock space truncation. Here we extend tBLFQ to include spatio-temporal field inhomogeneities in multiple spacetime directions. This extension is necessary for the proper modeling of e.g. intense laser fields. We focus on the example of nonlinear Compton scattering of an electron on an axicon-type laser, with an emphasis on the transverse structure of the beam. We analyze the impact of field intensity and particle energy, as well as basis truncation effects, on the radiation spectrum of the scattered electron. [ABSTRACT FROM AUTHOR]

As a toy model for QED in strong background fields, we consider the impact of backreaction and loop effects on scattering processes in quantum optics. We show that neglecting backreaction misses qualitative and quantitative features of strong-field physics. We are able to study an analog of the Narozhny-Ritus conjecture on the scaling of higher loop diagrams with intensity: we prove that there is no corresponding behavior in our model. Implications for QED are identified and discussed. [ABSTRACT FROM AUTHOR]

We present an exactly solvable example of coherent quantum interference effects in the creation of electron-positron pairs from the collision of a photon with ultrashort laser pulses. Being characterized entirely by null, or lightlike, directions, this setup realizes an all-optical double-slit in the "null" domain, and exhibits features both in common with, and distinct from, a time domain double-slit (Ramsey interferometer). We show that by tailoring the order and amplitude of the pulses one can control signatures of both quantum and classical physics in the produced positron spectrum. [ABSTRACT FROM AUTHOR]

We give exact results for the emission spectra of both nonlinear Breit-Wheeler pair production and nonlinear Compton scattering in ultraintense, ultrashort duration plane wave backgrounds, modeled as delta-function pulses. This includes closed form expressions for total scattering probabilities. We show explicitly that these probabilities do not exhibit the power-law scaling with intensity associated with the conjectured breakdown of (Furry picture) perturbation theory, instead scaling logarithmically in the high-intensity limit. [ABSTRACT FROM AUTHOR]

We consider the absorption of probe photons by electrons in the presence of an intense, pulsed, background field. Our analysis reveals an interplay between regularization and gauge invariance which distinguishes absorption from its crossing-symmetric processes, as well as a physical interpretation of absorption in terms of degenerate processes in the weak field limit. In the strong field limit we develop a locally constant field approximation (LCFA) for absorption which also exhibits new features. We benchmark the LCFA against analytical calculations and explore its regime of validity. Pulse shape effects are also investigated, as well as infrared and collinear limits of the absorption process. [ABSTRACT FROM AUTHOR]

Strong background fields require a nonperturbative treatment, which is afforded in QED by the Furry expansion of scattering amplitudes. It has been conjectured that this expansion breaks down for sufficiently strong fields, based on the asymptotic growth of loop corrections with increasing "quantum nonlinearity," essentially the product of field strength and particle energy. However, calculations to date have assumed that the background is constant. We show here, using general plane waves of finite duration, that observables at high quantum nonlinearity scale differently depending on whether intensity or energy is large. We find that, at high energy, loop contributions to observables tend to fall with increasing quantum nonlinearity, rather than grow. [ABSTRACT FROM AUTHOR]

Truncating quantum field theories to a dominant mode offers a nonperturbative approach to their solution. We consider here the interaction of charged scalar matter with a single mode of the electromagnetic field. The implied breaking of explicit Lorentz invariance prompts us to compare instant-form quantization and front form, with the latter yielding significant simplifications when light-front zero modes are included. Using these field theory results we reassess the validity of existing first-quantized approaches to depletion effects in strong laser fields, and propose an alternative interpretation based on the dressing approach to QED and its infrared structure. [ABSTRACT FROM AUTHOR]

There are many situations in which a strong electromagnetic field may be approximated as a fixed background. Going beyond this approximation, i.e. accounting for the backreaction of quantum processes on the field, is however challenging. Here we develop an approach to this problem which is a straightforward extension of background field methods. The approach follows from the observation that scattering in an on-shell background is equivalent to scattering between coherent states; we show that by deforming these states one can model backreaction. Focussing on intense laser-matter interactions, we provide examples which model beam depletion and, furthermore, introduce an extremization principle with which to determine the level of depletion in a given scattering process. [ABSTRACT FROM AUTHOR]

Showers of γ rays and positrons are produced when a high-energy electron beam collides with a superintense laser pulse. We present scaling laws for the electron-beam energy loss, the γ-ray spectrum, and the positron yield and energy that are valid in the nonlinear, radiation-reaction-dominated regime. As an application we demonstrate that by employing the collision of a >GeV electron beam with a laser pulse of intensity >5×1021Wcm-2, today's high-intensity laser facilities are capable of producing O(104) positrons per shot via light-by-light scattering. [ABSTRACT FROM AUTHOR]

We investigate deviations from the plane wave model in the interaction of charged particles with strong electromagnetic fields. A general result is that integrability of the dynamics is lost when going from lightlike to timelike or spacelike field dependence. For a special scenario in the classical regime we show how the radiation spectrum in the spacelike (undulator) case becomes well-approximated by the plane wave model in the high-energy limit, despite the two systems being Lorentz inequivalent. In the quantum problem, there is no analogue of the WKB-exact Volkov solution. Nevertheless, WKB and uniform-WKB approaches give good approximations in all cases considered. Other approaches that reduce the underlying differential equations from second to first order are found to miss the correct physics for situations corresponding to barrier transmission and wide-angle scattering. [ABSTRACT FROM AUTHOR]

We consider violation of Lorentz invariance in QED induced by a very high frequency background wave. An effective theory is obtained by averaging observables over the rapid field oscillations. This preserves Ward identities and restores translation invariance below the high-frequency scale, but only partial Lorentz invariance: we show that the effective theory is C-invariant SIM(2)-QED in very special relativity. Averaging leads to the nonlocal terms familiar from SIM(2) theories, while the short-distance behavior of the background field fermion propagator generates the infinite number of higher-order vertices of SIM(2)-QED. [ABSTRACT FROM AUTHOR]

Presents letters to the editor referencing articles and topics discussed in previous issues of the "Journal of Accountancy." Relevance of accounting to the needs and problems of contemporary society; Audit applications of the APSAM computer program; Functions of the audit of a public stock company.

We derive a simple expression for the photon helicity and polarization-flip probabilities in arbitrary background fields, in the low-energy regime. Taking the background to model a focused laser beam, we study the impact of pulse shape and collision geometry on the probabilities and on ellipticity signals of vacuum birefringence. We find that models which do not account for pulse duration can overestimate all signals in near head-on collisions by up to an order of magnitude. Taking pulse duration into account, the flip probability becomes relatively insensitive to both angular incidence and the fine details of the pulse structure. [ABSTRACT FROM AUTHOR]

Vacuum birefringence is governed by the amplitude for a photon to flip helicity or polarization state in an external field. Here, we calculate the flip and nonflip amplitudes in arbitrary plane wave backgrounds, along with the induced spacetime-dependent refractive indices of the vacuum. We compare the behavior of the amplitudes in the low energy and high energy regimes, and analyze the impact of pulse shape and energy. We also provide the first lightfront-QED derivation of the coefficients in the Heisenberg-Euler effective action. [ABSTRACT FROM AUTHOR]

Abstract: Hamiltonian light-front quantum field theory provides a framework for calculating both static and dynamic properties of strongly interacting relativistic systems. Invariant masses, correlated parton amplitudes and time-dependent scattering amplitudes, possibly with strong external time-dependent fields, represent a few of the important applications. By choosing the light-front gauge and adopting an orthonormal basis function representation, we obtain a large, sparse, Hamiltonian matrix eigenvalue problem for mass eigenstates that we solve by adapting ab initio no-core methods of nuclear many-body theory. In the continuum limit, the infinite matrix limit, we recover full covariance. Guided by the symmetries of light-front quantized theory, we adopt a two-dimensional harmonic oscillator basis for transverse modes that corresponds with eigensolutions of the soft-wall anti-de Sitter/quantum chromodynamics (AdS/QCD) model obtained from light-front holography. We outline our approach and present results for non-linear Compton scattering, evaluated non-perturbatively, where a strong and time-dependent laser field accelerates the electron and produces states of higher invariant mass i.e. final states with photon emission. [Copyright &y& Elsevier]

We show that the emission of soft photons via nonlinear Compton scattering in a pulsed plane wave (laser field) is in general infrared divergent. We give examples of both soft and soft-collinear divergences, and we pay particular attention to the case of crossed fields in both classical and quantum theories. [ABSTRACT FROM AUTHOR]

Abstract: We give a simple tutorial introduction to the Mathematica package STRINGVACUA, which is designed to find vacua of string-derived or inspired four-dimensional supergravities. The package uses powerful algebro-geometric methods, as implemented in the free computer algebra system Singular, but requires no knowledge of the mathematics upon which it is based. A series of easy-to-use Mathematica modules are provided which can be used both in string theory and in more general applications requiring fast polynomial computations. The use of these modules is illustrated throughout with simple examples. Program summary: Program title: STRINGVACUA Catalogue identifier: AEBZ_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEBZ_v1_0.html Program obtainable from: CPC Program Library, Queen''s University, Belfast, N. Ireland Licensing provisions: GNU GPL No. of lines in distributed program, including test data, etc.: 31 050 No. of bytes in distributed program, including test data, etc.: 163 832 Distribution format: tar.gz Programming language: “Mathematica” syntax Computer: Home and office spec desktop and laptop machines, networked or stand alone Operating system: Windows XP (with Cygwin), Linux, Mac OS, running Mathematica V5 or above RAM: Varies greatly depending on calculation to be performed Classification: 11.1 External routines: Linux: The program “Singular” is called from Mathematica. Windows: “Singular” is called within the Cygwin environment from Mathematica. Nature of problem: A central problem of string-phenomenology is to find stable vacua in the four-dimensional effective theories which result from compactification. Solution method: We present an algorithmic method, which uses techniques of algebraic geometry, to find all of the vacua of any given string-phenomenological system in a huge class. Running time: Varies greatly depending on calculation requested. [Copyright &y& Elsevier]

The Landau-Lifshitz equation is the first in an infinite series of approximations to the Lorentz-Abraham-Dirac equation obtained from "reduction of order." We show that this series is divergent, predicting wildly different dynamics at successive perturbative orders. Iterating reduction of order ad infinitum in a constant crossed field, we obtain an equation of motion which is free of the erratic behavior of perturbation theory. We show that Borel-Padé resummation of the divergent series accurately reproduces the dynamics of this equation, using as little as two perturbative coefficients. Comparing with the Lorentz-Abraham-Dirac equation, our results show that for large times the optimal order of truncation typically amounts to using the Landau-Lifshitz equation, but that this fails to capture the resummed dynamics over short times. [ABSTRACT FROM AUTHOR]

QED perturbation theory in a background field has been conjectured to break down for sufficiently high field intensity. The high-intensity behavior of a field theory is however intertwined with its high-energy (UV) behavior. Here we show that a UV modification of QED changes the high-intensity behavior of observables. Specifically we study nonlinear Compton scattering in a constant crossed field in QED with an additional Pauli term. In the UV modified theory the cross section exhibits a faster power-law scaling with intensity than in ordinary QED. [ABSTRACT FROM AUTHOR]

Abstract: An outstanding goal of physics is to find solutions that describe hadrons in the theory of strong interactions, Quantum Chromodynamics (QCD). For this goal, the light-front Hamiltonian formulation of QCD (LFQCD) is a complementary approach to the well-established lattice gauge method. LFQCD offers access to the hadrons' nonperturbative quark and gluon amplitudes, which are directly testable in experiments at existing and future facilities. We present an overview of the promises and challenges of LFQCD in the context of unsolved issues in QCD that require broadened and accelerated investigation. We identify specific goals of this approach and address its quantifiable uncertainties. [Copyright &y& Elsevier]