3,363 research outputs found
Letter to the Editor: 1H, 15N, and 13C chemical shift assignments of the resuscitation promoting factor domain of Rv1009 from Mycobacterium tuberculosis
International audienceNo abstract availabl
Dbl3 drives Cdc42 signaling at the apical margin to regulate junction position and apical differentiation
Epithelial cells develop morphologically characteristic apical domains that are bordered by tight junctions, the apical–lateral border. Cdc42 and its effector complex Par6–atypical protein kinase c (aPKC) regulate multiple steps during epithelial differentiation, but the mechanisms that mediate process-specific activation of Cdc42 to drive apical morphogenesis and activate the transition from junction formation to apical differentiation are poorly understood. Using a small interfering RNA screen, we identify Dbl3 as a guanine nucleotide exchange factor that is recruited by ezrin to the apical membrane, that is enriched at a marginal zone apical to tight junctions, and that drives spatially restricted Cdc42 activation, promoting apical differentiation. Dbl3 depletion did not affect junction formation but did affect epithelial morphogenesis and brush border formation. Conversely, expression of active Dbl3 drove process-specific activation of the Par6–aPKC pathway, stimulating the transition from junction formation to apical differentiation and domain expansion, as well as the positioning of tight junctions. Thus, Dbl3 drives Cdc42 signaling at the apical margin to regulate morphogenesis, apical–lateral border positioning, and apical differentiation
An integrated source of spectrally filtered correlated photons for large scale quantum photonic systems
We demonstrate the generation of quantum-correlated photon-pairs combined
with the spectral filtering of the pump field by more than 95dB using Bragg
reflectors and electrically tunable ring resonators. Moreover, we perform
demultiplexing and routing of signal and idler photons after transferring them
via a fiber to a second identical chip. Non-classical two-photon temporal
correlations with a coincidence-to-accidental ratio of 50 are measured without
further off-chip filtering. Our system, fabricated with high yield and
reproducibility in a CMOS process, paves the way toward truly large-scale
quantum photonic circuits by allowing sources and detectors of single photons
to be integrated on the same chip.Comment: 4 figure
Nonlinear characterisation of a silicon integrated Bragg waveguide filter
Bragg waveguides are promising optical filters for pump suppression in
spontaneous Four-Wave Mixing (FWM) photon sources. In this work, we investigate
the generation of unwanted photon pairs in the filter itself. We do this by
taking advantage of the relation between spontaneous and classical FWM, which
allows for the precise characterisation of the nonlinear response of the
device. The pair generation rate estimated from the classical measurement is
compared with the theoretical value calculated by means of a full quantum model
of the filter, which also allows to investigate the spectral properties of the
generated pairs. We find a good agreement between theory and experiment,
confirming that stimulated FWM is a valuable approach to characterise the
nonlinear response of an integrated filter, and that the pairs generated in a
Bragg waveguide are not a serious issue for the operation of a fully integrated
nonclassical source
Energy correlations of photon pairs generated by a silicon microring resonator probed by Stimulated Four Wave Mixing
Compact silicon integrated devices, such as micro-ring resonators, have
recently been demonstrated as efficient sources of quantum correlated photon
pairs. The mass production of integrated devices demands the implementation of
fast and reliable techniques to monitor the device performances. In the case of
time-energy correlations, this is particularly challenging, as it requires high
spectral resolution that is not currently achievable in coincidence
measurements. Here we reconstruct the joint spectral density of photons pairs
generated by spontaneous four-wave mixing in a silicon ring resonator by
studying the corresponding stimulated process, namely stimulated four wave
mixing. We show that this approach, featuring high spectral resolution and
short measurement times, allows one to discriminate between nearly-uncorrelated
and highly-correlated photon pairs.Comment: 7 pages, 4 figure
Improved nutrient digestibility and retention partially explains feed efficiency gains in pigs selected for low residual feed intake
Residual feed intake (RFI) is a unique measure of feed efficiency (FE) and an alternative to traditional measures. The RFI is defined as the difference between the actual feed intake of a pig and its expected feed intake based on a given amount of growth and backfat. Therefore, selecting pigs with a low RFI (LRFI) results in a more feed-efficient animal for a given rate of growth. Our objective was to determine the extent to which apparent total tract digestibility of nutrients and energy use and retention may explain FE differences between pigs divergently selected for LRFI or high RFI (HRFI). After 7 generations of selection, 12 HRFI and 12 LRFI pigs (62 ± 3 kg BW) were randomly assigned to metabolism crates. Pigs had free access to a standard diet based on corn (Zea mays) and soybean (Glycine max) meal containing 0.4% TiO2, an exogenous digestibility marker. After a 7-d acclimation, total urine and feces were collected for 72 h. Nutrient and energy digestibility, P digestibility, and N balance were then measured and calculated to determine differences between the RFI lines. As expected, ADFI was lower (2.0 vs. 2.6 kg; P \u3c 0.01), ADG did not differ, and FE was higher in the LRFI (P \u3c 0.001) compared to the HRFI pigs. The digestibility values for DM (87.3 vs. 85.9%), N (88.3 vs. 86.1%), and GE (86.9 vs. 85.4%) were higher (P ≤ 0.003) in the LRFI vs. HRFI pigs, respectively. The DE (16.59 vs. 16.32 MJ/kg DM) and ME (15.98 vs. 15.72 MJ/kg DM) values were also greater (P \u3c 0.001) in LRFI pigs. When correcting for ADFI, P digestibility did not differ between the lines. However, the LRFI pigs tended to have improved N retention (P = 0.08) compared to HRFI pigs (36.9 vs. 32.1 g/d). In conclusion, the higher energy and nutrient digestibility, use, and retention may partially explain the superior FE seen in pigs selected for LRFI
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