92 research outputs found
Production and state-selective detection of ultracold, ground state RbCs molecules
Using resonance-enhanced two-photon ionization, we detect ultracold,
ground-state RbCs molecules formed via photoassociation in a laser-cooled
mixture of 85Rb and 133Cs atoms. We obtain extensive bound-bound excitation
spectra of these molecules, which provide detailed information about their
vibrational distribution, as well as spectroscopic data on the RbCs ground
a^3\Sigma^+ and excited (2)^3\Sigma^+, (1)^1\Pi states. Analysis of this data
allows us to predict strong transitions from observed excited levels to the
absolute vibronic ground state of RbCs, potentially allowing the production of
stable, ultracold polar molecules at rates as large as 10^7 s^{-1}
Superconducting nanowire photon number resolving detector at telecom wavelength
The optical-to-electrical conversion, which is the basis of optical
detectors, can be linear or nonlinear. When high sensitivities are needed
single-photon detectors (SPDs) are used, which operate in a strongly nonlinear
mode, their response being independent of the photon number. Nevertheless,
photon-number resolving (PNR) detectors are needed, particularly in quantum
optics, where n-photon states are routinely produced. In quantum communication,
the PNR functionality is key to many protocols for establishing, swapping and
measuring entanglement, and can be used to detect photon-number-splitting
attacks. A linear detector with single-photon sensitivity can also be used for
measuring a temporal waveform at extremely low light levels, e.g. in
long-distance optical communications, fluorescence spectroscopy, optical
time-domain reflectometry. We demonstrate here a PNR detector based on parallel
superconducting nanowires and capable of counting up to 4 photons at
telecommunication wavelengths, with ultralow dark count rate and high counting
frequency
Dynamical decoupling and noise spectroscopy with a superconducting flux qubit
The characterization and mitigation of decoherence in natural and artificial
two-level systems (qubits) is fundamental to quantum information science and
its applications. Decoherence of a quantum superposition state arises from the
interaction between the constituent system and the uncontrolled degrees of
freedom in its environment. Within the standard Bloch-Redfield picture of
two-level system dynamics, qubit decoherence is characterized by two rates: a
longitudinal relaxation rate Gamma1 due to the exchange of energy with the
environment, and a transverse relaxation rate Gamma2 = Gamma1/2 + Gamma_phi
which contains the pure dephasing rate Gamma_phi. Irreversible energy
relaxation can only be mitigated by reducing the amount of environmental noise,
reducing the qubit's internal sensitivity to that noise, or through multi-qubit
encoding and error correction protocols (which already presume ultra-low error
rates). In contrast, dephasing is in principle reversible and can be refocused
dynamically through the application of coherent control pulse methods. In this
work we demonstrate how dynamical-decoupling techniques can moderate the
dephasing effects of low-frequency noise on a superconducting qubit with
energy-relaxation time T1 = 1/Gamma1 = 12 us. Using the CPMG sequence with up
to 200 pi-pulses, we demonstrate a 50-fold improvement in the transverse
relaxation time T2 over its baseline value. We observe relaxation-limited times
T2(CPMG) = 23 us = 2 T1 resulting from CPMG-mediated Gaussian pure-dephasing
times in apparent excess of 100 us. We leverage the filtering property of this
sequence in conjunction with Rabi and energy relaxation measurements to
facilitate the spectroscopy and reconstruction of the environmental noise power
spectral density.Comment: 21 pages (incl. 11-page appendix); 4 (+7) figure
ÎłCOP Is Required for Apical Protein Secretion and Epithelial Morphogenesis in Drosophila melanogaster
Background: There is increasing evidence that tissue-specific modifications of basic cellular functions play an important role in development and disease. To identify the functions of COPI coatomer-mediated membrane trafficking in Drosophila development, we were aiming to create loss-of-function mutations in the ÎłCOP gene, which encodes a subunit of the COPI coatomer complex.
Principal Findings: We found that ÎłCOP is essential for the viability of the Drosophila embryo. In the absence of zygotic ÎłCOP activity, embryos die late in embryogenesis and display pronounced defects in morphogenesis of the embryonic epidermis and of tracheal tubes. The coordinated cell rearrangements and cell shape changes during tracheal tube morphogenesis critically depend on apical secretion of certain proteins. Investigation of tracheal morphogenesis in ÎłCOP loss-of-function mutants revealed that several key proteins required for tracheal morphogenesis are not properly secreted into the apical lumen. As a consequence, ÎłCOP mutants show defects in cell rearrangements during branch elongation, in tube dilation, as well as in tube fusion. We present genetic evidence that a specific subset of the tracheal defects in ÎłCOP mutants is due to the reduced secretion of the Zona Pellucida protein Piopio. Thus, we identified a critical target protein of COPI-dependent secretion in epithelial tube morphogenesis.
Conclusions/Significance: These studies highlight the role of COPI coatomer-mediated vesicle trafficking in both general and tissue-specific secretion in a multicellular organism. Although COPI coatomer is generally required for protein secretion, we show that the phenotypic effect of ÎłCOP mutations is surprisingly specific. Importantly, we attribute a distinct aspect of the ÎłCOP phenotype to the effect on a specific key target protein
Intracellular lumen extension requires ERM-1-dependent apical membrane expansion and AQP-8-mediated flux
SUMMARY Many unicellular tubes such as capillaries form lumens intracellularly, a process that is not well understood. Here we show that the cortical membrane organizer ERM-1 is required to expand the intracellular apical/lumenal membrane and its actin undercoat during single-cell C.elegans excretory canal morphogenesis. We characterize AQP-8, identified in an ERM-1 overexpression (ERM-1[++]) suppressor screen, as a canalicular aquaporin that interacts with ERM-1 in lumen extension in a mercury-sensitive manner, implicating water-channel activity. AQP-8 is transiently recruited to the lumen by ERM-1, co-localizing in peri-lumenal cuffs interspaced along expanding canals. An ERM-1[++]-mediated increase in the number of lumen-associated canaliculi is reversed by AQP-8 depletion. We propose that the ERM-1-AQP-8 interaction propels lumen extension by translumenal flux, suggesting a direct morphogenetic effect of water-channel-regulated fluid pressure
Endoscopic Delivery of Fecal Biotherapy in Inflammatory Bowel Disease
The intestinal microbiome plays an important role in the pathogenesis of inflammatory bowel disease (IBD). We are able to use the microbiome as a therapeutic target with use of fecal microbiota transplantation (FMT) for cure of recurrent Clostridium difficile infection. Given our ability to target the dysbiotic state with FMT, its use as therapy in IBD has tremendous potential. This overview discusses the practical considerations of FMT therapy with respect to our current understanding of safety and efficacy in IBD, screening for donors and recipients, specimen handling and storage, methods of delivery, and regulatory considerations
Gut Microbiota and Inflammatory Bowel Disease: The Role of Antibiotics in Disease Management
Imbalances in the composition and number of bacteria in the gut microbiota have been implicated in inflammatory bowel disease (IBD), and modulation of the gut microbiota by probiotics and antibiotics in IBD has been an active area of research, with mixed results. This narrative review summarizes the findings of relevant publications identified using the PubMed database. Although antibiotics have been associated with an increased risk of IBD development and flares, several meta-analyses demonstrate that antibiotics are efficacious for the induction of remission and treatment of flares in patients with IBD. Data supporting their use include a large number of antibiotic studies in Crohn's disease and evidence suggests antibiotics are efficacious in both Crohn's disease and ulcerative colitis, although there are fewer studies of the latter. For Crohn's disease, antibiotics have been shown to be useful for the induction of remission and in the postoperative management of patients undergoing surgery. Additionally, patients with fistulizing disease, particularly perianal, can benefit from antibiotics administered short term. Both antimicrobials and probiotics have been shown to be useful for the treatment of pouchitis. Additional randomized controlled trials are needed to further elucidate the role of bacteria in IBD and to better inform clinicians about appropriate antibiotic therapies
Description of a new Nebria (Eunebria) species from Iran (Coleoptera, Carabidae: Nebriini) and faunistic data for Nebria (Eunebria) xanthacra xanthacra CHAUDOIR, 1850
W, David, H, Peer, P, Kerman, K, N (2017): Description of a new Nebria (Eunebria) species from Iran (Coleoptera, Carabidae: Nebriini) and faunistic data for Nebria (Eunebria) xanthacra xanthacra CHAUDOIR, 1850. Linzer biologische Beiträge 49 (1): 927-935, DOI: http://doi.org/10.5281/zenodo.540941
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