Characterization and epidemiology of influenza viruses in patients seeking treatment for influenza-like illnesses in rural Bangladesh.

CONTEXT: Infections caused by influenza viruses are a major health burden, both in developed and developing countries worldwide. Nevertheless, the overwhelming majority of influenza reports originate from industrialized countries in northern and southern temperate zones. AIMS: The aim of this study was to determine the epidemiology of influenza viruses in patients seeking treatment for acute febrile illnesses in rural Bangladesh. SETTINGS AND DESIGN: As part of our research on the causes of febrile illnesses in rural Bangladesh, nasopharyngeal swabs from patients with signs and symptoms consistent with influenza were collected from 2008 onwards. MATERIALS AND METHODS: Viral infection was established using two independent rapid diagnostic tests (RDTs) and later confirmed by RT-PCR. RESULTS: A total of 314 fever cases were enrolled in a survey of febrile illnesses carried out in Bandarban District in southeastern Bangladesh, out of whom 38 (12.1%) tested positive by RDT. Molecular subtyping showed that seasonal H3 strains (N=22; 7.0%) as well as the new H1N1v pandemic influenza subtype (N=13; 4.1%) had been circulating at the time of our investigations resulting in a PCR-adjusted positivity rate of 11.1% (95% CI 8.0 - 15.3). The positive predictive values for the RDTs used were 90.9% and 94.4%, respectively. CONCLUSIONS: This study provides a first insight into influenza epidemics in one of the most remote parts of Asia. Our findings suggest that respiratory illnesses due to influenza viruses are underreported in areas with limited access to health care and show a distinct seasonality also in rural areas of tropical countries.

Neutron optical beam splitter from holographically structured nanoparticle-polymer composites.

We report a breakthrough in the search for versatile diffractive elements for cold neutrons. Nanoparticles are spatially arranged by holographical means in a photopolymer. These grating structures show remarkably efficient diffraction of cold neutrons up to about 50% for effective thicknesses of only 200   µm. They open up a profound perspective for next generation neutron-optical devices with the capability to tune or modulate the neutron diffraction efficiency.

Temperature dependence of optical anisotropy of holographic polymer-dispersed liquid crystal transmission gratings.

We measured the angular dependence of the 0th, +/-1 st, and +/-2 nd optical diffraction orders from a 50 microm thick transmission grating recorded in a UV-curable holographic polymer-dispersed liquid crystal (HPDLC) made from commercially available constituents. The analysis was performed for two orthogonal polarizations of the probe beams. The emphasis was laid on the temperature dependence of the grating anisotropy. Above the nematic-isotropic phase transition, the grating is optically isotropic. At lower temperatures the grating strength for the optical polarization perpendicular to the grating vector decreases with decreasing temperature, while for orthogonal polarization it increases with decreasing temperature. As a consequence, a regime of diffraction with strongly overmodulated gratings is observed. Our investigations indicate that the anisotropy of the refractive-index modulation scales with the optical anisotropy of the liquid crystal medium forming the phase-separated domains. We further demonstrate that light scattering effects, which are profound only in the nematic phase, must not be neglected and can be taken into account via a Lorentzian line-shape broadening of the probing wave vector directions in the framework of the diffraction theory for anisotropic optical phase gratings.

Light-induced extinction originating from holographic scattering.

We present extinction spectra of sodium nitroprusside exhibiting holographic light scattering after irradiation with coherent light. A characteristic extinction band appearing in the vicinity of the wavelength of the pump beam was discovered as well as an increase of the extinction coefficient over the whole spectral range. These features are proved to originate from diffraction of the probe beam from parasitic holograms and can be explained within the framework of a simple Ewald construction.