On the interaction of a single-photon wave packet with an excited atom

The interaction of a single-photon wave packet with an initially excited two-level atom in free space is studied in semiclassical and quantum approaches. It is shown that the final state of the field does not contain doubly occupied modes. The process of the atom's transition to the ground state may be accelerated, decelerated or even reversed by the incoming photon, depending on parameters. The spectrum of emitted radiation is close to the sum of the spectrum of the incoming single-photon wave packet and the natural line shape, with small and complicated deviations.Comment: 17 pages, 5 figure

Ponderomotive entangling of atomic motions

We propose the use of ponderomotive forces to entangle the motions of different atoms. Two situations are analyzed: one where the atoms belong to the same optical cavity and interact with the same radiation field mode; the other where each atom is placed in own optical cavity and the output field of one cavity enters the other.Comment: Revtex file, five pages, two eps figure

Ultrathin 2 nm gold as ideal impedance-matched absorber for infrared light

Thermal detectors are a cornerstone of infrared (IR) and terahertz (THz) technology due to their broad spectral range. These detectors call for suitable broad spectral absorbers with minimalthermal mass. Often this is realized by plasmonic absorbers, which ensure a high absorptivity butonly for a narrow spectral band. Alternativly, a common approach is based on impedance-matching the sheet resistance of a thin metallic film to half the free-space impedance. Thereby, it is possible to achieve a wavelength-independent absorptivity of up to 50 %, depending on the dielectric properties of the underlying substrate. However, existing absorber films typicallyrequire a thickness of the order of tens of nanometers, such as titanium nitride (14 nm), whichcan significantly deteriorate the response of a thermal transducers. Here, we present the application of ultrathin gold (2 nm) on top of a 1.2 nm copper oxide seed layer as an effective IR absorber. An almost wavelength-independent and long-time stable absorptivity of 47(3) %, ranging from 2 $\mu$m to 20 $\mu$m, could be obtained and is further discussed. The presented gold thin-film represents analmost ideal impedance-matched IR absorber that allows a significant improvement of state-of-the-art thermal detector technology

A multicentre matched case control study of risk factors for Preeclampsia in healthy women in Pakistan

<p>Abstract</p> <p>Background</p> <p>Preeclampsia is one of the leading causes of maternal and perinatal morbidity and mortality world-wide. The risk for developing preeclampsia varies depending on the underlying mechanism. Because the disorder is heterogeneous, the pathogenesis can differ in women with various risk factors. Understanding these mechanisms of disease responsible for preeclampsia as well as risk assessment is still a major challenge. The aim of this study was to determine the risk factors associated with preeclampsia, in healthy women in maternity hospitals of Karachi and Rawalpindi.</p> <p>Methods</p> <p>We conducted a hospital based matched case-control study to assess the factors associated with preeclampsia in Karachi and Rawalpindi, from January 2006 to December 2007. 131 hospital-reported cases of PE and 262 controls without history of preeclampsia were enrolled within 3 days of delivery. Cases and controls were matched on the hospital, day of delivery and parity. Potential risk factors for preeclampsia were ascertained during in-person postpartum interviews using a structured questionnaire and by medical record abstraction. Conditional logistic regression was used to estimate matched odds ratios (ORs) and 95% confidence intervals (95% CIs).</p> <p>Results</p> <p>In multivariate analysis, women having a family history of hypertension (adjusted OR 2.06, 95% CI; 1.27-3.35), gestational diabetes (adjusted OR 6.57, 95% CI; 1.94 -22.25), pre-gestational diabetes (adjusted OR 7.36, 95% CI; 1.37-33.66) and mental stress during pregnancy (adjusted OR 1.32; 95% CI; 1.19-1.46, for each 5 unit increase in Perceived stress scale score) were at increased risk of preeclampsia. However, high body mass index, maternal age, urinary tract infection, use of condoms prior to index pregnancy and sociodemographic factors were not associated with higher risk of having preeclampsia.</p> <p>Conclusions</p> <p>Development of preeclampsia was associated with gestational diabetes, pregestational diabetes, family history of hypertension and mental stress during pregnancy. These factors can be used as a screening tool for preeclampsia prediction. Identification of the above mentioned predictors would enhance the ability to diagnose and monitor women likely to develop preeclampsia before the onset of disease for timely interventions and better maternal and fetal outcomes.</p

Quantum interference in three-photon down-conversion

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Alzheimer's Disease: a Review of its Visual System Neuropathology. Optical Coherence Tomography-a Potential Role As a Study Tool in Vivo

Alzheimer's disease (AD) is a prevalent, long-term progressive degenerative disorder with great social impact. It is currently thought that, in addition to neurodegeneration, vascular changes also play a role in the pathophysiology of the disease. Visual symptoms are frequent and are an early clinical manifestation; a number of psychophysiologic changes occur in visual function, including visual field defects, abnormal contrast sensitivity, abnormalities in color vision, depth perception deficits, and motion detection abnormalities. These visual changes were initially believed to be solely due to neurodegeneration in the posterior visual pathway. However, evidence from pathology studies in both animal models of AD and humans has demonstrated that neurodegeneration also takes place in the anterior visual pathway, with involvement of the retinal ganglion cells' (RGCs) dendrites, somata, and axons in the optic nerve. These studies additionally showed that patients with AD have changes in retinal and choroidal microvasculature. Pathology findings have been corroborated in in-vivo assessment of the retina and optic nerve head (ONH), as well as the retinal and choroidal vasculature. Optical coherence tomography (OCT) in particular has shown great utility in the assessment of these changes, and it may become a useful tool for early detection and monitoring disease progression in AD. The authors make a review of the current understanding of retinal and choroidal pathological changes in patients with AD, with particular focus on in-vivo evidence of retinal and choroidal neurodegenerative and microvascular changes using OCT technology.info:eu-repo/semantics/publishedVersio

Preparation of nonclassical states in cavities with a moving mirror

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