623 research outputs found
Urinary tract lesions due to SCHISTOSOMA HAEMATOBIUM infection assessed by ultrasonography in a community based study in Niger
Ultrasonographic assessment of urinary tract lesions due to Schistosoma haematobium in Niger after four consecutive years of treatment with praziquantel
Une étude comparative sur l'étendue des lésions du tractus urinaire détectées par échographie a été entreprise dans 2 villages du Niger situés près de périmètres irrigués. La prévalence de la schistosomiase urinaire était respectivement de 64,3 % et de 58,8 %. Après un traitement au praziquantel de 4 années consécutives, les lésions vésicales atteignaient 20 % dans le village traité et 54 % dans le témoin, les lésions rénales 6 % dans le village traité et 36 % dans le témoin. Ces résultats montrent que la morbidité de la schistosomiase urinaire peut être réduite par un traitement annuel sur plusieurs années sans autre forme d'interventio
Gain without population inversion in V-type systems driven by a frequency-modulated field
We obtain gain of the probe field at multiple frequencies in a closed
three-level V-type system using frequency modulated pump field. There is no
associated population inversion among the atomic states of the probe
transition. We describe both the steady-state and transient dynamics of this
system. Under suitable conditions, the system exhibits large gain
simultaneously at series of frequencies far removed from resonance. Moreover,
the system can be tailored to exhibit multiple frequency regimes where the
probe experiences anomalous dispersion accompanied by negligible
gain-absorption over a large bandwidth, a desirable feature for obtaining
superluminal propagation of pulses with negligible distortion.Comment: 10 pages + 8 figures; To appear in Physical Review
Vertical-external-cavity surface-emitting lasers and quantum dot lasers
The use of cavity to manipulate photon emission of quantum dots (QDs) has
been opening unprecedented opportunities for realizing quantum functional
nanophotonic devices and also quantum information devices. In particular, in
the field of semiconductor lasers, QDs were introduced as a superior
alternative to quantum wells to suppress the temperature dependence of the
threshold current in vertical-external-cavity surface-emitting lasers
(VECSELs). In this work, a review of properties and development of
semiconductor VECSEL devices and QD laser devices is given. Based on the
features of VECSEL devices, the main emphasis is put on the recent development
of technological approach on semiconductor QD VECSELs. Then, from the viewpoint
of both single QD nanolaser and cavity quantum electrodynamics (QED), a
single-QD-cavity system resulting from the strong coupling of QD cavity is
presented. A difference of this review from the other existing works on
semiconductor VECSEL devices is that we will cover both the fundamental aspects
and technological approaches of QD VECSEL devices. And lastly, the presented
review here has provided a deep insight into useful guideline for the
development of QD VECSEL technology and future quantum functional nanophotonic
devices and monolithic photonic integrated circuits (MPhICs).Comment: 21 pages, 4 figures. arXiv admin note: text overlap with
arXiv:0904.369
Kank Is an EB1 Interacting Protein that Localises to Muscle-Tendon Attachment Sites in Drosophila
Little is known about how microtubules are regulated in different cell types during development. EB1 plays a central role in the regulation of microtubule plus ends. It directly binds to microtubule plus ends and recruits proteins which regulate microtubule dynamics and behaviour. We report the identification of Kank, the sole Drosophila orthologue of human Kank proteins, as an EB1 interactor that predominantly localises to embryonic attachment sites between muscle and tendon cells. Human Kank1 was identified as a tumour suppressor and has documented roles in actin regulation and cell polarity in cultured mammalian cells. We found that Drosophila Kank binds EB1 directly and this interaction is essential for Kank localisation to microtubule plus ends in cultured cells. Kank protein is expressed throughout fly development and increases during embryogenesis. In late embryos, it accumulates to sites of attachment between muscle and epidermal cells. A kank deletion mutant was generated. We found that the mutant is viable and fertile without noticeable defects. Further analysis showed that Kank is dispensable for muscle function in larvae. This is in sharp contrast to C. elegans in which the Kank orthologue VAB-19 is required for development by stabilising attachment structures between muscle and epidermal cells
Lasing without inversion in three-level systems without external coherent driving
We have studied an incoherently pumped laser operating with a Doppler-broadened three-level system placed in a doubly resonant cavity. This system generates two laser fields, one of them without population inversion. Both ladder and V-type three-level schemes are considered with a ratio R=ωα/ωβ of inversionless laser frequency ωα to ordinary laser frequency ωβ of R=0.67 and R=1.88, respectively. Dual-wavelength lasing extends up to Doppler-broadening values for optical transitions of atoms in a vapor cell. Some considerations for the practical realization of this dual-wavelength laser are discussed
Electromagnetically induced transparency with a standing-wave drive in the frequency up-conversion regime
We study electromagnetically induced transparency for a probe traveling-wave (TW) laser field in closed Doppler-broadened three-level systems driven by a standing-wave (SW) laser field of moderate intensity (its Rabi frequencies are smaller than the Doppler width of the driven transition). We show that probe windows of transparency occur for values of the probe to drive field frequency ratio R close to half-integer values. For optical transitions and typical values of Doppler broadening for atoms in a vapor cell, we show that for R>1 a SW drive field is appreciably more efficient than a TW drive in inducing probe transparency. As examples, we consider parameters for real cascade schemes in barium atoms with R≈1.5 and in beryllium atoms with R≈3.5 showing that probe transmission values well above 50% are possible for conditions in which it is almost negligible either without driving field or with only one of the TW components of the drive. We show that a strongly asymmetric drive having two TW components with unequal intensities is even more eficient than a symmetric SW drive in inducing probe transparency. The case of arbitrary probe intensity is also considered
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