Medical disorders in pregnancy

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Lateral loss effects on modulation bandwidth in VCSELs

Intensity noise and chromatic fiber dispersion in analog optical communication systems are attributed to harmonic and inter-modulation distortion in the amplitude modulation of semiconductor lasers. In addition, maximum usable bandwidth of the communication systems is limited by harmonic distortion. Due to the use of Fabry Perot type resonator, second harmonic distortion exists in both edge-emitting devices and VCSELs. However the distortion caused by lateral loss may be more so in VCSELs because of its smaller core size. Two factors, namely, the lateral field confinement factor and the lateral loss due to diffraction, are considered for their effect on harmonic distortion when the laser device is under small signal modulation.published_or_final_versio

Second-harmonic distortion in vertical-cavity surface-emitting lasers with lateral loss effects

The influence of lateral loss effects on the second-harmonic distortion (SHD) of vertical-cavity surface-emitting lasers is investigated theoretically. Two parameters, differential confinement factor and differential cavity loss, are defined for the consideration of self-focusing and diffraction loss. It is found that SHD increases at low modulation frequencies due to the presence of differential cavity loss, especially for lasers with small core radius.published_or_final_versio

Assessment of regional systolic and diastolic impairment of left ventricular function: a study with tissue doppler imaging on right ventricular pacing

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Assessment of regional systolic and diastolic impairment on left ventricular function: a study with tissue Doppler imaging on right ventricular pacing

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Ultra-short silicon-organic hybrid (SOH) modulator for bidirectional polarization-independent operation

We propose a bidirectional, polarization-independent, recirculating IQ-modulator scheme based on the silicon-organic hybrid (SOH) platform. We demonstrate the viability of the concept by using an SOH Mach-Zehnder modulator, operated at 10 GBd BPSK and 2ASK-2PSK

Simultaneous dual-band optical coherence tomography for endoscopic applications

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Big bang simulation in superfluid 3He-B -- Vortex nucleation in neutron-irradiated superflow

We report the observation of vortex formation upon the absorption of a thermal neutron in a rotating container of superfluid $^3$He-B. The nuclear reaction n + $^3$He = p + $^3$H + 0.76MeV heats a cigar shaped region of the superfluid into the normal phase. The subsequent cooling of this region back through the superfluid transition results in the nucleation of quantized vortices. Depending on the superflow velocity, sufficiently large vortex rings grow under the influence of the Magnus force and escape into the container volume where they are detected individually with nuclear magnetic resonance. The larger the superflow velocity the smaller the rings which can expand. Thus it is possible to obtain information about the morphology of the initial defect network. We suggest that the nucleation of vortices during the rapid cool-down into the superfluid phase is similar to the formation of defects during cosmological phase transitions in the early universe.Comment: 4 pages, LaTeX file, 4 figures are available at ftp://boojum.hut.fi/pub/publications/lowtemp/LTL-95009.p

Cryotomography of budding influenza a virus reveals filaments with diverse morphologies that mostly do not bear a genome at their distal end

Influenza viruses exhibit striking variations in particle morphology between strains. Clinical isolates of influenza A virus have been shown to produce long filamentous particles while laboratory-adapted strains are predominantly spherical. However, the role of the filamentous phenotype in the influenza virus infectious cycle remains undetermined. We used cryo-electron tomography to conduct the first three-dimensional study of filamentous virus ultrastructure in particles budding from infected cells. Filaments were often longer than 10 microns and sometimes had bulbous heads at their leading ends, some of which contained tubules we attribute to M1 while none had recognisable ribonucleoprotein (RNP) and hence genome segments. Long filaments that did not have bulbs were infrequently seen to bear an ordered complement of RNPs at their distal ends. Imaging of purified virus also revealed diverse filament morphologies; short rods (bacilliform virions) and longer filaments. Bacilliform virions contained an ordered complement of RNPs while longer filamentous particles were narrower and mostly appeared to lack this feature, but often contained fibrillar material along their entire length. The important ultrastructural differences between these diverse classes of particles raise the possibility of distinct morphogenetic pathways and functions during the infectious process