Longitudinal Photon Research Articles

A Computer-Aided Analysis Method of SPECT Brain Images for Quantitative Treatment Monitoring: Performance Evaluations and Clinical Applications.

The objective and quantitative analysis of longitudinal single photon emission computed tomography (SPECT) images are significant for the treatment monitoring of brain disorders. Therefore, a computer aided analysis (CAA) method is introduced to extract a change-rate map (CRM) as a parametric image for quantifying the changes of regional cerebral blood flow (rCBF) in longitudinal SPECT brain images. The performances of the CAA-CRM approach in treatment monitoring are evaluated by the computer simulations and clinical applications. The results of computer simulations show that the derived CRMs have high similarities with their ground truths when the lesion size is larger than system spatial resolution and the change rate is higher than 20%. In clinical applications, the CAA-CRM approach is used to assess the treatment of 50 patients with brain ischemia. The results demonstrate that CAA-CRM approach has a 93.4% accuracy of recovered region's localization. Moreover, the quantitative indexes of recovered regions derived from CRM are all significantly different among the groups and highly correlated with the experienced clinical diagnosis. In conclusion, the proposed CAA-CRM approach provides a convenient solution to generate a parametric image and derive the quantitative indexes from the longitudinal SPECT brain images for treatment monitoring.

Ratios of helicity amplitudes for exclusiveρ0electroproduction on transversely polarized proton

Exclusive ρ 0 -meson electroproduction is studied by the HERMES experiment, using the 27.6 GeV longitudinally polarized electron/positron beam of HERA and a transversely polarized hydrogen target, in the kinematic region 1.0 GeV 2 Q 2 2 , 3.0 GeV t ′ 2 . Using an unbinned maximum-likelihood method, 25 parameters are extracted. They determine the real and imaginary parts of the ratios of certain helicity amplitudes describing ρ 0 -meson production by a virtual photon, where the denominator is the dominant amplitude . The latter is the nucleon-helicity-non-flip amplitude, which describes the production of a longitudinal ρ 0 meson by a longitudinal virtual photon. The transverse target polarization allows for the first time the extraction of ratios of a number of nucleon-helicity-flip amplitudes to . The ratios of nucleon-helicity-non-flip amplitudes are found to be in good agreement with those from the previous HERMES analysis.

Dipole factorization for DIS at NLO: Loop correction to theγT,L*→qq¯light-front wave functions

The one-loop QCD corrections to the light-front wave-function for the quark-antiquark Fock state inside a transverse or longitudinal off-shell photon are explicitly calculated, both in full momentum space and in mixed space (a.k.a. dipole space). These results provide one of the main contributions to virtual NLO corrections to many DIS observables (inclusive or not) in the dipole factorization formalism at low Bjorken x. In a follow-up article, these one-loop corrections are combined with earlier results on the wave-function for the quark-antiquark-gluon Fock state, in order to get the full set of NLO corrections to the DIS structure functions $F_2$ and $F_L$ in the dipole factorization formalism, valid at low Bjorken x.

Shot-to-shot diagnostic of the longitudinal photon source position at the SPring-8 Angstrom Compact Free Electron Laser by means of x-ray grating interferometry.

We present single-shot measurements of the longitudinal photon source position of the SPring-8 Angstrom Compact Free Electron Laser x-ray free electron laser by means of x-ray grating interferometry. The measurements were performed in order to study the behavior of the source under normal operation conditions and as a dependence on the active undulator length. The retrieved experimental results show that x-ray grating interferometry is a powerful in situ monitoring tool for investigating and tuning an x-ray free electron laser.

Chiral imbalance induced by longitudinal photons in a charged magnetized QED plasma

AbstractWe demonstrate the existence of a chiral magnetic effect in an electron‐positron magnetized gas in QED. A vector current is induced by the electric field related to the pseudo‐vector longitudinal Debye massive photon mode propagating along the external magnetic field B and separating opposite charges of the same helicity. A equation associated to the nonconservation of the axial current is obtained in a medium of massive and magnetized charged fermions. The effect is interesting in connection to the QCD chiral magnetic case reported in current literature. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Suppressing longitudinal spatial hole burning with dual assisted phase shifts in pitch-modulated DFB lasers

An equivalent corrugation pitch-modulated (ECPM) distributed feedback (DFB) semiconductor laser with two equivalently assisted phase shifts (EAPS) was theoretically studied and experimentally demonstrated. The simulated results showed that the longitudinal photon density distribution of the ECPM + EAPS DFB lasers was much more uniform than that of a sole ECPM DFB laser without EAPS, and the longitudinal spatial hole burning was therefore suppressed more effectively. The results of experiment showed that good single longitudinal mode operation was achieved, with side mode suppression ratio (SMSR) being over 35dB, and the wavelength range was from 1,559.64 to 1,563.02nm when the operation current was from 50 to 160mA at the temperature of 25 °C, and the SMSR increased to 46.29dB when the injection current was 130mA.

Identification of diabetes-related dementia: Longitudinal perfusion SPECT and amyloid PET studies

AimsWe attempted to identify a dementia subgroup with characteristics associated with diabetes mellitus (DM)-related metabolic abnormalities, referred to as diabetes-related dementia, using longitudinal single photon emission computed tomography (SPECT) and Pittsburgh compound-B (PiB) positron emission tomography (PET). MethodsWe classified 175 patients with clinically diagnosed Alzheimer disease (AD) and DM into 4 subgroups based on brain imaging in a 2013 study. Among them, we investigated follow-up SPECT studies in 29 patients of an AD group showing decreased regional cerebral blood flow (rCBF) of the parietotemporal lobe on initial SPECT and 18 patients of a diabetes-related dementia group showing neither decreased rCBF of the parietotemporal lobe nor cerebrovascular disease, which is strongly associated with DM-related factors. Eleven of them underwent PiB PET. ResultsFollow-up SPECT showed more profound rCBF reduction in the parietotemporal lobe and other areas of the AD group, whereas follow-up SPECT showed an rCBF reduction in small areas of the frontotemporal and limbic lobes of the diabetes-related dementia group. Six of 9 patients with diabetes-related dementia were negative or equivocal for PiB binding. ConclusionA subset of a dementia subgroup with characteristics predominantly associated with DM-related factors may underlie a pathophysiology different from AD, although these patients were clinically diagnosed as having AD. The identification of diabetes-related dementia may be necessary for considering an appropriate therapy and prevention in clinical practice.

Rate of progression of Alzheimer's disease in younger versus older patients: A longitudinal single photon emission computed tomography study

Although several researchers have examined the effect of age on disease progression in patients with Alzheimer's disease (AD), the results are controversial. We investigated the effect of age on the rate of progression of cognitive impairment and on regional cerebral blood flow (rCBF) deficits using longitudinal single photon emission computed tomography (SPECT) studies. We divided 75 patients with AD who were followed up for 24-90 months into the younger AD group (n=32, age at initial examination ≤ 75 years) and the older AD group (n=43, age at initial examination >75 years). We assessed changes in Mini-Mental State Examination (MMSE) scores and rCBF between initial and final examinations. The change in the annual MMSE score was greater in the younger AD group than in the older AD group. The mean annual MMSE score changes correlated significantly with age at the initial examination. The initial and follow-up SPECT studies showed more severe and extensive rCBF deficits in the younger AD group than in the older AD group. Our longitudinal SPECT study showed that the rate of progression of cognitive impairment and the rCBF deficits were higher in younger patients with AD than in older patients with AD. Therefore, age is an important factor to consider, not only in the diagnosis, but also in the treatment and prognosis of patients with AD.

Exclusive ρ0 production in deep inelastic scattering at HERA

Exclusive ρ0 electroproduction at HERA has been studied with the ZEUS detector using 120 pb−1 of integrated luminosity collected during 1996-2000. The analysis was carried out in the kinematic range of photon virtuality 2 < Q2 < 160 GeV2 and γ∗p centre-of-mass energy 32 < W < 180 GeV. The results include the Q2 and W dependence of the γ∗p → ρ0p cross section and the distribution of the squared-four-momentum transfer to the proton. The helicity analysis of the decay-matrix elements of the ρ0 was used to study the ratio of the γ∗p cross section for longitudinal and transverse photon as a function of Q2, W and t. Finally, an effective Pomeron trajectory was extracted.

The Clinical Analysis of General Paresis With 5 Cases

The Clinical Analysis of General Paresis With 5 Cases

The color dipole picture and the ratio of [formula omitted

The transverse size of q q ¯ fluctuations of the longitudinal photon is reduced relative to the transverse size of q q ¯ fluctuations of the transverse photon. This implies R ( W 2 , Q 2 ) = 0.375 or, equivalently, F L / F 2 = 0.27 at x ≪ 0.1 and Q 2 sufficiently large, while R ( W 2 , Q 2 ) = 0.5 , if this effect is not taken into account. Forthcoming experimental data from HERA will allow to test this prediction.

Near-field photon wave mechanics in the Lorenz gauge

Optical near-field interactions are studied theoretically in the perspective of photon wave mechanics paying particular attention to the dynamics in the wave-vector time domain. A unitary transformation is used to replace the scalar and longitudinal photon variables by so-called near-field and gauge photon variables. Dynamical equations are established for these types of photon variables, and it is shown that these equations are invariant against gauge transformations within the Lorenz gauge. The near-field photon is absent in the free-field limit, and the gauge photon can be eliminated by a suitable gauge transformation. Implicit solutions for the near-field, gauge, and transverse photon variables are obtained and discussed. The general theory is applied to an investigation of transverse photon propagation in a uniform solid-state plasma dominated by the diamagnetic field-matter interaction. It is found that the diamagnetic response can be incorporated in a quantum mechanical wave equation for a massive transverse photon. The Compton wave number of the massive photon equals the plasma wave number of the electron system. A dynamical equation describing the emission of a massive transverse photon from a mesoscopic source embedded in the plasma is finally established.

Exclusive ρ0 production in deep inelastic scattering at HERA

Exclusive rho^0 electroproduction at HERA has been studied with the ZEUS detector using 120 pb^{-1} of integrated luminosity collected during 1996-2000. The analysis was carried out in the kinematic range of photon virtuality 2 < Q^2 < 160 GeV$^2, and gamma^* p centre-of-mass energy 32 < W < 180 GeV. The results include the Q^2 and W dependence of the gamma^* p --> rho^0 p cross section and the distribution of the squared-four-momentum transfer to the proton. The helicity analysis of the decay-matrix elements of the rho^0 was used to study the ratio of the gamma^* p cross section for longitudinal and transverse photon as a function of Q^2 and W. Finally, an effective Pomeron trajectory was extracted. The results are compared to various theoretical predictions.

Quasielastic rho-meson knockout from nucleons by high-energy electrons

The electroproduction of charged rho mesons on a nucleon under conditions of quasielastic kinematics [Q 2 > 2 (GeV/c)2, W > 3 GeV, and ω ρ ≃ q 0 in the laboratory frame] is considered. The main diagrams involved in this process are taken into account, and it is shown that the case of rho-meson knockout by a longitudinal photon is dominated by the t-channel pole diagram featuring a rho meson, so that direct rho-meson electroknockout makes a leading contribution to the process being considered. Questions concerning the gauge invariance of the electroproduction process are considered in detail, along with contact terms that inevitably arise in employing form factors in ρNN vertices and which are necessary for restoring gauge invariance. It is shown that the structure of these contact terms is not determined exclusively by the requirement that the electroproduction amplitude be gauge-invariant and may be such that the corresponding correction to the dominant diagram due to these terms proves to be suppressed in the quasielastic region (with increasing Q 2), with the result that the t-pole process featuring a rho meson remains dominant; at the same time, the contribution of this correction is significant at low Q 2 or in the case of photoproduction, modifying substantially the electroproduction cross section.

Vortex duality: Observing the dual nature using order propagators

In condensed matter physics, Kramers-Wannier duality implies that the state disordered by quantum fluctuations or temperature actually corresponds to an ordered state formed from the topological excitations of the ``original'' ordered state. At first sight it might appear to be impossible to observe this dual order using means associated with the original order. Although true for Ising models, we demonstrate in this paper that this is not a general statement by considering the well-known vortex duality, in particular in the quantum interpretation in $2+1\mathrm{D}$ where it is associated with the quantum phase transition from a superfluid to a Bose Mott insulator. Here, the disordered Mott insulating state is at the same time a dual superconductor corresponding to a Bose condensate of vortices. We present a simple formalism making it possible to compute the velocity propagator associated with the superfluid in terms of the degrees of freedom of the dual theory. The Mott insulator is characterized by a doublet of massive modes, and we demonstrate that one of these modes is nothing else than the longitudinal photon (gauged second sound) of the dual superconductor. For increasing momenta, the system rediscovers the original order, and the effect on the velocity correlator is that the longitudinal photon loses its pole strength. The quantum critical regime as probed by the velocity correlator is most interesting. We demonstrate that at infinite wavelength the continua of critical modes associated with second sound and the dual longitudinal photon are indistinguishable. However, at finite momenta they behave differently, tracking the weight reshuffling found in the quasiparticle spectrum of the disorder state closely.

OFF-SHELL PHOTON LONGITUDINAL LIGHT-CONE WAVE FUNCTION AT LEADING TWIST

The leading twist longitudinal virtual photon light-cone wave function, ϕγ‖(u, P2), is calculated within the framework of the low-energy effective theory arising from the instanton model of QCD vacuum. Corresponding to the non-perturbative effects at low-energy scale, a suitable regularization scale T is fixed by analysing the differential behavior of the photon wave function on the internal transverse momentum cut-off in the light-cone frame. The coupling constant, Fγ(P2), of the quark-antiquark vector current to the virtual photon state is also obtained by imposing the normalization condition. The feature of the obtained photon wave function has been discussed at the end as well as the coupling constant.

Off-Shell Longitudinal Photon Light-Cone Wavefunction in theLow-Energy Effective Theory of QCD

Within the framework of the low-energy effective theory arisingfrom the instanton vacuum model of QCD, the longitudinal virtualphoton light-cone wavefunction, ϕγ∥(u,P2),corresponding to the nonlocal quark–antiquark vector current iscalculated at the low-energy scale. The coupling constant,Fγ(P2) or equivalently fγ(P2), of thequark–antiquark vector current to the virtual photon state is alsoobtained by imposing the normalization condition to the photon wavefunction. The behaviour of the coupling constant as well as the obtainedphoton wavefunction is discussed.

On the theory of spatial photon localization: Fundamentals and the role of near-field plasma screening

Starting from the Riemann-Silberstein formulation of classical electrodynamics the Schrödinger equation for the photon energy wave function is discussed. Hereafter, a propagator description of the space-time emission of a polychromatic photon from an atom is presented, paying particular attention to the near-field electrodynamics. When the atom is embedded in a solid-state plasma the photon emission process can be dramatically modified. Limiting the analyses to solid-state plasmas exhibiting translational and rotational symmetry, the near-field atom-photon-plasma interaction is studied paying particular attention to the plasmariton and plasmon excitation processes. It is shown that the transverse and longitudinal parts of the plasma-screened field propagator link in a direct manner to the free-photon propagator and the longitudinal near-field photon propagator. The necessity of keeping both the transverse and longitudinal parts of the plasma screening in a rigorous description of near-field electrodynamics is demonstrated.

Virtual photon asymmetry for confined, interacting Dirac particles with spin symmetry

We study the Bjorken x dependence of the virtual photon spin asymmetry in polarized deep inelastic scattering of electrons from hadrons. We use an exactly solved relativistic potential model of the hadron, treating the constituents as independent massless Dirac particles bound to an infinitely massive force center. The potential is chosen to have spin symmetry and a linear radial dependence with spherical symmetry. The effect of interactions of the struck constituent with the remainder of the target on the longitudinal photon asymmetry is demonstrated. In particular, the small-x suppression of the photon asymmetry observed in polarized deep inelastic scattering from the proton is shown to be a consequence of these interactions. The effect of p-wave components of the Dirac wave function, long known to give an important contribution to the spin of hadrons, is explicitly demonstrated through their interference with the s-wave term.

Generating Ultralow-Emittance Ion Beams in a Storage Ring

Laser cooling of heavy-ion beams in a storage ring is systematically studied with a multiparticle simulation code where not only exact lattice characteristics and space-charge forces but also realistic laser-ion interactions can be incorporated. The resonant coupling method is applied in order to extend the powerful longitudinal photon pressure to the transverse degrees of freedom. It is shown that, in spite of a space-charge-induced tune shift, the synchrobetatron resonance mechanism required for fast damping of transverse oscillations operates throughout the cooling process. Extremely efficient three-dimensional cooling of stored ion beams is thus feasible. It is demonstrated that, at low line density, normalized root-mean-squared emittances of the order of 10(-12) m.rad can be reached in all three directions by employing only existing technologies.