Theoretical analysis of mechanical displacement measurement using a multiple cavity mode transducer

We present an optomechanical displacement transducer, that relies on three cavity modes parametrically coupled to a mechanical oscillator and whose frequency spacing matches the mechanical resonance frequency. The additional resonances allow to reach the standard quantum limit at substantially lower input power (compared to the case of only one resonance), as both, sensitivity and quantum backaction are enhanced. Furthermore, it is shown that in the case of multiple cavity modes, coupling between the modes is induced via reservoir interaction, e.g., enabling quantum backaction noise cancellation. Experimental implementation of the schemes is discussed in both the optical and microwave domain.Comment: 5 pages, 3 figures. Revised and amended versio

Parametric Normal-Mode Splitting in Cavity Optomechanics

Recent experimental progress in cavity optomechanics has allowed cooling of mesoscopic mechanical oscillators via dynamic backaction provided by the parametric coupling to either an optical or an electrical resonator. Here we analyze the occurrence of normal-mode splitting in backaction cooling at high input power. We find that a hybridization of the oscillator's motion with the fluctuations of the driving field occurs and leads to a splitting of the mechanical and optical fluctuation spectra. Moreover, we find that cooling experiences a classical limitation through the cavity lifetime.Comment: 4 pages, 3 figure

Genome sequence of the fish brain bacterium Clostridium tarantellae

Eubacterium tarantellae was originally cultivated from the brain of fish affected by twirling movements. Here, we present the draft genome sequence of E. tarantellae DSM 3997, which consists of 3,982,316 bp. Most protein-coding genes in this strain are similar to genes of Clostridium bacteria, supporting the renaming of E. tarantellae as Clostridium tarantellae

Determination of the vacuum optomechanical coupling rate using frequency noise calibration

The strength of optomechanical interactions in a cavity optomechanical system can be quantified by a vacuum coupling rate \vcr analogous to cavity quantum electrodynamics. This single figure of merit removes the ambiguity in the frequently quoted coupling parameter defining the frequency shift for a given mechanical displacement, and the effective mass of the mechanical mode. Here we demonstrate and verify a straightforward experimental technique to derive the vacuum optomechanical coupling rate. It only requires applying a known frequency modulation of the employed electromagnetic probe field and knowledge of the mechanical oscillator's occupation. The method is experimentally verified for a micromechanical mode in a toroidal whispering-gallery-resonator and a nanomechanical oscillator coupled to a toroidal cavity via its near field.Comment: 11 pages, 2 figure

Sideband Cooling Micromechanical Motion to the Quantum Ground State

The advent of laser cooling techniques revolutionized the study of many atomic-scale systems. This has fueled progress towards quantum computers by preparing trapped ions in their motional ground state, and generating new states of matter by achieving Bose-Einstein condensation of atomic vapors. Analogous cooling techniques provide a general and flexible method for preparing macroscopic objects in their motional ground state, bringing the powerful technology of micromechanics into the quantum regime. Cavity opto- or electro-mechanical systems achieve sideband cooling through the strong interaction between light and motion. However, entering the quantum regime, less than a single quantum of motion, has been elusive because sideband cooling has not sufficiently overwhelmed the coupling of mechanical systems to their hot environments. Here, we demonstrate sideband cooling of the motion of a micromechanical oscillator to the quantum ground state. Entering the quantum regime requires a large electromechanical interaction, which is achieved by embedding a micromechanical membrane into a superconducting microwave resonant circuit. In order to verify the cooling of the membrane motion into the quantum regime, we perform a near quantum-limited measurement of the microwave field, resolving this motion a factor of 5.1 from the Heisenberg limit. Furthermore, our device exhibits strong-coupling allowing coherent exchange of microwave photons and mechanical phonons. Simultaneously achieving strong coupling, ground state preparation and efficient measurement sets the stage for rapid advances in the control and detection of non-classical states of motion, possibly even testing quantum theory itself in the unexplored region of larger size and mass.Comment: 13 pages, 7 figure

Meningeal lymphatic endothelial cells fulfill scavenger endothelial cell function and cooperate with microglia in waste removal from the brain

Brain lymphatic endothelial cells (BLECs) constitute a group of loosely connected endothelial cells that reside within the meningeal layer of the zebrafish brain without forming a vascular tubular system. BLECs have been shown to readily endocytose extracellular cargo molecules from the brain parenchyma, however, their functional relevance in relation to microglia remains enigmatic. We here compare their functional uptake efficiency for several macromolecules and bacterial components with microglia in a qualitative and quantitative manner in 5-day-old zebrafish embryos. We find BLECs to be significantly more effective in the uptake of proteins, polysaccharides and virus particles as compared to microglia, while larger particles like bacteria are only ingested by microglia but not by BLECs, implying a clear distribution of tasks between the two cell types in the brain area. In addition, we compare BLECs to the recently discovered scavenger endothelial cells (SECs) of the cardinal vein and find them to accept an identical set of substrate molecules. Our data identifies BLECs as the first brain-associated SEC population in vertebrates, and demonstrates that BLECs cooperate with microglia to remove particle waste from the brain.Thrombosis and Hemostasi

Genomic aberrations after short-term exposure to colibactin-producing E. coli transform primary colon epithelial cells

Genotoxic colibactin-producing pks+ Escherichia coli induce DNA double-strand breaks, mutations, and promote tumor development in mouse models of colorectal cancer (CRC). Colibactin’s distinct mutational signature is reflected in human CRC, suggesting a causal link. Here, we investigate its transformation potential using organoids from primary murine colon epithelial cells. Organoids recovered from short-term infection with pks+ E. coli show characteristics of CRC cells, e.g., enhanced proliferation, Wnt-independence, and impaired differentiation. Sequence analysis of Wnt-independent organoids reveals an enhanced mutational burden, including chromosomal aberrations typical of genomic instability. Although we do not find classic Wnt-signaling mutations, we identify several mutations in genes related to p53-signaling, including miR-34a. Knockout of Trp53 or miR-34 in organoids results in Wnt-independence, corroborating a functional interplay between the p53 and Wnt pathways. We propose larger chromosomal alterations and aneuploidy as the basis of transformation in these organoids, consistent with the early appearance of chromosomal instability in CRC

Genomic Islands as a Marker to Differentiate between Clinical and Environmental Burkholderia pseudomallei

Burkholderia pseudomallei, as a saprophytic bacterium that can cause a severe sepsis disease named melioidosis, has preserved several extra genes in its genome for survival. The sequenced genome of the organism showed high diversity contributed mainly from genomic islands (GIs). Comparative genome hybridization (CGH) of 3 clinical and 2 environmental isolates, using whole genome microarrays based on B. pseudomallei K96243 genes, revealed a difference in the presence of genomic islands between clinical and environmental isolates. The largest GI, GI8, of B. pseudomallei was observed as a 2 sub-GI named GIs8.1 and 8.2 with distinguishable %GC content and unequal presence in the genome. GIs8.1, 8.2 and 15 were found to be more common in clinical isolates. A new GI, GI16c, was detected on chromosome 2. Presences of GIs8.1, 8.2, 15 and 16c were evaluated in 70 environmental and 64 clinical isolates using PCR assays. A combination of GIs8.1 and 16c (positivity of either GI) was detected in 70% of clinical isolates and 11.4% of environmental isolates (P<0.001). Using BALB/c mice model, no significant difference of time to mortality was observed between K96243 isolate and three isolates without GIs under evaluation (P>0.05). Some virulence genes located in the absent GIs and the difference of GIs seems to contribute less to bacterial virulence. The PCR detection of 2 GIs could be used as a cost effective and rapid tool to detect potentially virulent isolates that were contaminated in soil

Quantum noise in a nano mechanical Duffing resonator

We determine the small signal gain and noise response of an amplifier based on the nonlinear response of a quantum nanomechanical resonator. The resonator is biased in the nonlinear regime by a strong harmonic bias force and we determine the response to a small additional driving signal detuned with respect to the bias force.Comment: submitted to the Focus Issue on 'Mechanical Systems at the Quantum Limit', edited by Markus Aspelmeyer and Keith Schwa

The host metabolite D-serine contributes to bacterial niche specificity through gene selection

Escherichia coli comprise a diverse array of both commensals and niche-specific pathotypes. The ability to cause disease results from both carriage of specific virulence factors and regulatory control of these via environmental stimuli. Moreover, host metabolites further refine the response of bacteria to their environment and can dramatically affect the outcome of the host–pathogen interaction. Here, we demonstrate that the host metabolite, D-serine, selectively affects gene expression in E. coli O157:H7. Transcriptomic profiling showed exposure to D-serine results in activation of the SOS response and suppresses expression of the Type 3 Secretion System (T3SS) used to attach to host cells. We also show that concurrent carriage of both the D-serine tolerance locus (dsdCXA) and the locus of enterocyte effacement pathogenicity island encoding a T3SS is extremely rare, a genotype that we attribute to an ‘evolutionary incompatibility’ between the two loci. This study demonstrates the importance of co-operation between both core and pathogenic genetic elements in defining niche specificity