227 research outputs found

    Spontaneous emission of an atomic dipole near a semi-transparent mirror in free space

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    Atom-field interactions near optical interfaces have a wide range of applications in quantum technology. Motivated by this, this paper revisits the spontaneous emission of atomic dipoles in the presence of a two sided semi-transparent mirror. First we review the main properties of the quantised electromagnetic field near a semitransparent mirror. To do so, we employ a quantum mirror image detector method which maps the experimental setup which we consider here onto analogous free space scenarios. We emphasise that the local density of states of the electromagnetic field depends on the reflection rates of both sides of the mirror surface. Hence it is not surprising that also the spontaneous decay rate of an atomic dipole in front of a semi-transparent mirror depends on both reflectance rates. Although the effect which we describe here only holds for relatively short atom-mirror distances, it can aid the design of novel photonics devices

    Plasmonic Band-Pass Microfilters for LWIR Absorption Spectroscopy

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    Absorption spectroscopy in the long wave infrared provides an effective method for identification of various hazardous chemicals. We present a theoretical design for plasmonic band-pass filters that can be used to provide wavelength selectivity for uncooled microbolometer sensors. The microfilters consist of a pair of input reflection gratings that couple light into a plasmonic waveguide with a central resonant waveguide cavity. An output transmission grating on the other side of the structure pulls light out of the waveguide where it is detected by a closely spaced sensor. Fabrication of the filters can be performed using standard photolithography procedures. A spectral bandpass with a full-width at half-maximum (FWHM) of 100 nm can be obtained with a center wavelength spanning the entire 8–12 μm atmospheric transmission window by simple geometric scaling of only the lateral dimensions. This allows the simultaneous fabrication of all the wavelength filters needed for a full spectrometer on a chip

    33 Brachyterapia przy użyciu irydu 192 w leczeniu pierwotnych glejaków mózgu

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    W okresie od listopada 1996 do listopada 1999 w Oddziale Brachyterapii Regionalnego Centrum Onkologii w Bydgoszczy i w Klinice Neurochirurgii 10 Wojskowego Szpitala Klinicznego w Bydgoszczy leczono 57 pacjentów z pierwotnymi guzami glejopochodnymi mózgu przy użyciu brachyterapii z zastosowaniem izotopu irydu-192. Dokładnej analizie poddano 25 pacjentów, którzy odpowiedzieli na ankietę (9 – z gwiaździakiem II stopnia, 1 – ze skąpodrzewiakiem II stopnia, 4 – z gwiaździakiem III stopnia, 1 – ze skapodrzewiakogwiaździakiem IIIstopnia, 10 – z glejakiem wielopostaciowym). Spośród 25 pacjentów, którzy odpowiedzieli na ankietę zmarło 13. Średni okres obserwacji wyniósł 43 tygodni (max.−157 tyg., min.−2 tyg.). Średni okres poprawy wyniósł 23 tygodnie (od 0 do 104 tygodni). Średni okres przeżycia wyniósł 31 tygodni (od 2 do 146 tygodni). Autorzy analizują czynniki wpływające na czas przeżycia (takie jak wiek, stopień złośliwości histopatologicznej guza, połątczenie brachyterapii z teleradioterapią) oraz na podstawie własnych doświadczeń określają wskazania i przeciwwskazania

    N-Glycosylation of ß4 Integrin Controls the Adhesion and Motility of Keratinocytes

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    α6ß4 integrin is an essential component of hemidesmosomes and modulates cell migration in wound healing and cancer invasion. To elucidate the role of N-glycosylation on ß4 integrin, we investigated keratinocyte adhesion and migration through the re-expression of wild-type or N-glycosylation-defective ß4 integrin (ΔNß4) in ß4 integrin null keratinocytes. N-glycosylation of ß4 integrin was not essential for the heterodimer formation of ß4 integrin with α6 integrin and its expression on a cell surface, but N-glycosylation was required for integrin-mediated cell adhesion and migration. Concomitantly with the reduction of ß4 integrin in the membrane microdomain, the intracellular signals of Akt and ERK activation were decreased in cells expressing ΔNß4 integrin. Forced cross-linking of ß4 integrin rescued the decreased ERK activation in ΔNß4 integrin-expressing cells to a similar extent in wild-type ß4 integrin-expressing cells. Surprisingly, compared with cells expressing wild-type ß4 integrin, an alternation in N-glycan structures expressed on epidermal growth factor receptor (EGFR), and the induction of a stronger association between EGFR and ß4 integrin were observed in ΔNß4 integrin-expressing cells. These results clearly demonstrated that N-glycosylation on ß4 integrin plays an essential role in keratinocyte cellular function by allowing the appropriate complex formation on cell surfaces

    The DEAD-box RNA Helicase DDX6 is Required for Efficient Encapsidation of a Retroviral Genome

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    Viruses have to encapsidate their own genomes during the assembly process. For most RNA viruses, there are sequences within the viral RNA and virion proteins needed for high efficiency of genome encapsidation. However, the roles of host proteins in this process are not understood. Here we find that the cellular DEAD-box RNA helicase DDX6 is required for efficient genome packaging of foamy virus, a spumaretrovirus. After infection, a significant amount of DDX6, normally concentrated in P bodies and stress granules, re-localizes to the pericentriolar site where viral RNAs and Gag capsid proteins are concentrated and capsids are assembled. Knockdown of DDX6 by siRNA leads to a decreased level of viral nucleic acids in extracellular particles, although viral protein expression, capsid assembly and release, and accumulation of viral RNA and Gag protein at the assembly site are little affected. DDX6 does not interact stably with Gag proteins nor is it incorporated into particles. However, we find that the ATPase/helicase motif of DDX6 is essential for viral replication. This suggests that the ATP hydrolysis and/or the RNA unwinding activities of DDX6 function in moderating the viral RNA conformation and/or viral RNA-Gag ribonucleoprotein complex in a transient manner to facilitate incorporation of the viral RNA into particles. These results reveal a unique role for a highly conserved cellular protein of RNA metabolism in specifically re-locating to the site of viral assembly for its function as a catalyst in retroviral RNA packaging
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