Elna M. Nagasako

Acute pain in herpes zoster: the famciclovir database project

&NA; The results of a considerable number of recent prospective studies have demonstrated that greater acute pain severity in herpes zoster patients is associated with a significantly greater risk of developing postherpetic neuralgia (PHN). Only a few studies have examined the relationships between acute pain severity and demographic characteristics and clinical features of patients with herpes zoster, however, and the results of these studies have been inconsistent. To clarify these relationships, data from 1778 herpes zoster patients studied within 72 h of rash onset in four clinical trials of the antiviral agent famciclovir were examined. Univariate and multivariate analyses indicated that greater acute pain severity was significantly associated with greater age, female sex, greater rash severity, the presence of a prodrome, and primary involvement of non‐trigeminal dermatomes. These results demonstrate that three of the established risk factors for PHN – older age, greater rash severity, and the presence of a prodrome – are also associated with more severe acute pain assessed soon after rash onset in patients with herpes zoster. The results of this study are consistent with the recommendation that herpes zoster patients who are older, who have had a prodrome, or who have severe rash or severe acute pain should be targeted for interventions designed to prevent PHN.

Prospects for the prevention of postherpetic neuralgia in herpes zoster patients.

Objective: Herpes zoster is a common and painful disease that is caused by reactivation of the varicella‐zoster virus. Herpes zoster pain that persists after healing of the acute infection is termed postherpetic neuralgia (PHN), a chronic pain syndrome that is often refractory to all treatment. The prevalence of PHN is expected to increase substantially in the coming decades, because the incidence of herpes zoster and the risk of PHN will both increase as the population ages. Although the results of recent studies provide a basis for improved treatment of patients with PHN, as many as half of all PHN patients do not obtain relief of their pain. Research on the development of improved treatments is continuing, but it has not been generally recognized that an equally important goal should be the design of interventions to prevent PHN. The prevention of PHN would lead to major reductions in disability, suffering, and the use of health care resources. Design: The results of recent studies that have identified risk factors for the development of PHN and have implicated several peripheral and central mechanisms in its pathophysiology are reviewed. Outcome Measures: These risk factors and mechanisms of PHN provide a basis for hypothesizing that combining antiviral therapy with analgesic treatment beginning as soon as possible after the onset of herpes zoster would reduce the risk of PHN beyond that achieved by antiviral therapy alone. Conclusions: This treatment approach would be expected to reduce the risk of PHN in herpes zoster patients by attenuating acute pain and thereby preventing the initiation of central mechanisms of chronic pain.

Nonclassical two-photon interferometry and lithography with high-gain parametric amplifiers

Two-photon entangled states have been utilized in many configurations that exploit the novel fourth-order interferometric properties of these states, most recently in a proposal for the achievement of sub-Rayleigh-limit resolution [1]. While the interferometric properties of biphotons have been extensively analyzed under a variety of arrangements, the impact of multiphoton states on these properties has not been extensively explored.

Parametric downconversion vs optical parametric amplification: a comparison of their quantum statistics

The extent to which the intense light generated by an unseeded, high-gain optical parametric amplifier retains the desired quantum statistical properties of the individual photon pairs generated by spontaneous parametric downconversion is analysed. It is shown that certain but not all of these properties are retained, with important implications for applications of quantum optics.

Vacuum-induced jitter in spatial solitons

We perform a calculation to determine how quantum mechanical fluctuations influence the propagation of a spatial soliton through a nonlinear material. To do so, we derive equations of motion for the linearized operators describing the deviation of the soliton position and transverse momentum from those of a corresponding classical solution to the nonlinear wave equation, and from these equations we determine the quantum uncertainty in the soliton position and transverse momentum. We find that under realistic laboratory conditions the quantum uncertainty in position is several orders of magnitude smaller the classical width of the soliton. This result suggests that the reliability of photonic devices based on spatial solitons is not compromised by quantum fluctuations.

From Laser Beam Filamentation to Optical Solitons: The Influence of C. H. Townes on the Development of Modern Nonlinear Optics

Self-action effects began to be studied soon after the advent of the laser. Suddenly sources were available that could create beams of light which not only could influence the materials in which they were propagating, but could also, through this material interaction, act back on themselves. These self-action effects could alter the size and shape of the laser beam and introduce new spectral components. In this article, we single out self-focusing, and the associated phenomena of filamentation and the generation of spatial solitons, and describe how recent research has evolved from the pioneering contribution of C. H. Townes.

Quantum fluctuations as the origin of laser-beam filamentation

According to traditional theories, the filamentation1 of a laser beam as it passes through a nonlinear material is a consequence of the spatial growth2,3 of weak wavefront perturbations initially present on the beam. To a certain extent these perturbations can be removed by passing the beam through a spatial filter before it enters the medium. However, quantum fluctuations in the field amplitudes of the transverse side modes impose perturbations that cannot be removed by spatial filtering. These quantum fluctuations can lead to the filamentation of a beam with an otherwise perfect wavefront. We study the growth of these fluctuations and predict the nonlinear phase shift at which this process will become significant. We find that quantum-initiated filamentation imposes a fundamental limit to the intensities that can be propagated through a nonlinear material without beam breakup.

Signal-to-noise characteristics of nonlinear optical amplifiers

In this paper, we present the results of our theoretical and experimental studies of the noise properties of optical amplifiers that operate by means of nonlinear optical gain processes. We pay particular attention to amplifiers that utilize the nonlinear optical response of strongly driven atomic vapors, and we compare the results of our measurements with theoretical predictions for the quantum noise limit of an optical amplifier. Our work focuses on optical amplifiers that utilize the nonlinear optical response of atomic vapors.<<ETX>>