Inert strength measurement on silica soaked at 250°C in liquid water and water vapour

The effect of water soaking and heat-treatment in saturated water vapour at 250°C for 192 h on the strength of silica glass is studied. Bending strength meaurements in liquid nitrogen showed a clear increase of the inert strength for heat-treated specimens over that of the untreated material. The increase in strength is interpreted as the consequence of water diffusion into exposed surfaces of the test specimen, which results in swelling of the glass and shielding of cracks, present in the surface of the glass. Experimental results are compared with theoretical predictions

Impact of the indexed effective orifice area on mid-term cardiac-related mortality after aortic valve replacement

Background There has been ongoing controversy as to whether prosthesis-patient mismatch (PPM, defined as indexed effective orifice area (EOAI) <0.85 m(2)/cm(2)) influences mortality after aortic valve replacement (AVR). In most studies, PPM is anticipated by reference tables based on mean EOAs as opposed to individual assessment. These reference values may not reflect the actual in vivo EOAI and hence, the presence or absence of PPM may be based on false assumptions. Objective To assess the impact of small prosthesis EOA on survival after aortic valve replacement AVR. Methods 645 patients had undergone an AVR between 2000 and 2007 entered the study. All patients underwent transthoracic echocardiography for determination of the actual EOAI within 6 months postoperatively. In order to predict time from surgery to death a proportional hazards model for competing risks (cardiac death vs death from other causes) was used. EOAI was entered as a continuous variable. Results PPM occurred in 40% of the patients. After a median follow-up of 2.35 years, 92.1% of the patients were alive. The final Cox regression model showed a significantly increased risk for cardiac death among patients with a smaller EOAI (HR=0.32, p=0.022). The effect of EOAI on the 2-5 year mortality risk was demonstrated by risk plots. Conclusions In contrast to previous studies these EOAI values were obtained through postoperative echocardiography, substantially improving the accuracy of measurement, and the EOAI was modelled as a continuous variable. There was a significantly improved survival for larger EOAIs following AVR. Strategies to avoid PPM should become paramount during AVR

Evaluation of crack-terminating angles in heat-treated silica DCDC-specimens

Cracks terminating at free surfaces are affected by local stresses in the surface region. Under residual compression, the crack front must retard and under residual tensile stresses advance, both compared with the crack contour in the absence of stresses. This effect can be used for an estimation of residual surface stresses in silica generated during the silica/water reaction and caused by volume swelling. A strong shielding stress intensity factor of about -2.5 MPa$\sqrt{m}$ was found for DCDC specimen heat-treated for 192h at 250°C in water. This result is a clear indication for compressive stresses developing in the water diffusion zone at the surface

Lifetimes of Confined Acoustic Phonons in Ultra-Thin Silicon Membranes

We study the relaxation of coherent acoustic phonon modes with frequencies up to 500 GHz in ultra-thin free-standing silicon membranes. Using an ultrafast pump-probe technique of asynchronous optical sampling, we observe that the decay time of the first-order dilatational mode decreases significantly from \sim 4.7 ns to 5 ps with decreasing membrane thickness from \sim 194 to 8 nm. The experimental results are compared with theories considering both intrinsic phonon-phonon interactions and extrinsic surface roughness scattering including a wavelength-dependent specularity. Our results provide insight to understand some of the limits of nanomechanical resonators and thermal transport in nanostructures

Measuring the quantum efficiency of single radiating dipoles using a scanning mirror

Using scanning probe techniques, we show the controlled manipulation of the radiation from single dipoles. In one experiment we study the modification of the fluorescence lifetime of a single molecular dipole in front of a movable silver mirror. A second experiment demonstrates the changing plasmon spectrum of a gold nanoparticle in front of a dielectric mirror. Comparison of our data with theoretical models allows determination of the quantum efficiency of each radiating dipole.Comment: 4 pages, 4 figure

An ultra-sensitive pulsed balanced homodyne detector: Application to time-domain quantum measurements

A pulsed balanced homodyne detector has been developed for precise measurements of electric field quadratures of pulsed optical quantum states. A high level of common mode suppression (> 85 dB) and low electronic noise (730 electrons per pulse) provide a signal to noise ratio of 14 dB for the measurement of the quantum noise of individual pulses. Measurements at repetition rates up to 1 MHz are possible. As a test, quantum tomography of the coherent state is performed and the Wigner function and the density matrix are reconstructed with a 99.5% fidelity. The detection system can also be used for ultrasensitive balanced detection in cw mode, e.g. for weak absorption measurements.Comment: 3 pages, submitted to Optics Letter

Transcriptomic and proteomic insights into innate immunity and adaptations to a symbiotic lifestyle in the gutless marine worm Olavius algarvensis

Background: The gutless marine worm Olavius algarvensis has a completely reduced digestive and excretory system, and lives in an obligate nutritional symbiosis with bacterial symbionts. While considerable knowledge has been gained of the symbionts, the host has remained largely unstudied. Here, we generated transcriptomes and proteomes of O. algarvensis to better understand how this annelid worm gains nutrition from its symbionts, how it adapted physiologically to a symbiotic lifestyle, and how its innate immune system recognizes and responds to its symbiotic microbiota. Results: Key adaptations to the symbiosis include (i) the expression of gut-specific digestive enzymes despite the absence of a gut, most likely for the digestion of symbionts in the host's epidermal cells; (ii) a modified hemoglobin that may bind hydrogen sulfide produced by two of the worm's symbionts; and (iii) the expression of a very abundant protein for oxygen storage, hemerythrin, that could provide oxygen to the symbionts and the host under anoxic conditions. Additionally, we identified a large repertoire of proteins involved in interactions between the worm's innate immune system and its symbiotic microbiota, such as peptidoglycan recognition proteins, lectins, fibrinogen-related proteins, Toll and scavenger receptors, and antimicrobial proteins. Conclusions: We show how this worm, over the course of evolutionary time, has modified widely-used proteins and changed their expression patterns in adaptation to its symbiotic lifestyle and describe expressed components of the innate immune system in a marine oligochaete. Our results provide further support for the recent realization that animals have evolved within the context of their associations with microbes and that their adaptive responses to symbiotic microbiota have led to biological innovations

Estimation of swelling stresses from crack-terminating angles

Cracks terminating at free surfaces are affected by local stresses in the surface region. The crack front retards under residual compressive stresses compared with the crack contour in the absence of stresses. This effect had been used in [1] for identifying compression in the surface of chemically toughened and ion-exchanged soda-lime glass surfaces. In [2] the same effect was proven for swelling stresses due to the silica/water reaction. In the present report, the stresses in the surface layers are predicted based on results for soda-lime glass. For silica heattreated in humid environments, compressive stresses in the order of about -130 MPa to -170 MPa are obtained

Quantum control of proximal spins using nanoscale magnetic resonance imaging

Quantum control of individual spins in condensed matter systems is an emerging field with wide-ranging applications in spintronics, quantum computation, and sensitive magnetometry. Recent experiments have demonstrated the ability to address and manipulate single electron spins through either optical or electrical techniques. However, it is a challenge to extend individual spin control to nanoscale multi-electron systems, as individual spins are often irresolvable with existing methods. Here we demonstrate that coherent individual spin control can be achieved with few-nm resolution for proximal electron spins by performing single-spin magnetic resonance imaging (MRI), which is realized via a scanning magnetic field gradient that is both strong enough to achieve nanometric spatial resolution and sufficiently stable for coherent spin manipulations. We apply this scanning field-gradient MRI technique to electronic spins in nitrogen-vacancy (NV) centers in diamond and achieve nanometric resolution in imaging, characterization, and manipulation of individual spins. For NV centers, our results in individual spin control demonstrate an improvement of nearly two orders of magnitude in spatial resolution compared to conventional optical diffraction-limited techniques. This scanning-field-gradient microscope enables a wide range of applications including materials characterization, spin entanglement, and nanoscale magnetometry.Comment: 7 pages, 4 figure

Experimental calibration for DCDC specimens

The main advantages of DCDC-specimens are their completely stable crack extension properties and very high path stability due to the strongly negative T-stress term. Unfortunately, problems of DCDC tests can be identified by comparing experimental results that show for different materials (silicon nitride, glass) deviations from the results to be expected by 2-dimensional FE modelling as usual done in literature. Experimental calibrations on silicon nitrides and mixtures of silicon nitride and silicon carbide resulted in modified relations deviating from FE-results in literature. As a possible source for the differences of measurements and 2-D-FE results, we identified the influence of Poisson’s number. This parameter obviously causes deviations between straight-crack assumption in FEmodelling and observable curved crack fronts in the experiments. In order to avoid specimen buckling we also used short specimens of roughly half length. This may slightly affect the stress intensity factors