Temperature Dependence of Photoluminescence Intensity and Spin Contrast in Nitrogen-Vacancy Centers.

We report on measurements of the photoluminescence properties of single nitrogen-vacancy centers in diamond at temperatures between 4 K and 300 K. We observe a strong reduction of the PL intensity and spin contrast between ca. 10 K and 100 K that recovers to high levels below and above. Further, we find a rich dependence on magnetic bias field and crystal strain. We develop a comprehensive model based on spin mixing and orbital hopping in the electronic excited state that quantitatively explains the observations. Beyond a more complete understanding of the excited-state dynamics, our work provides a novel approach for probing electron-phonon interactions and a predictive tool for optimizing experimental conditions for quantum applications.

Surface imaging of breast implants using modern high-frequency ultrasound technology in comparison to high-end sonography with power analyses for B-scan optimization1.

AIM: This study aims to evaluate optimized breast implant surface-structure analysis by comparing high-end ultrasound technology with a new high frequency technique. This comparative study used new breast implants with different surfaces in an in vitro setting. METHODS: Nine idle silicon or polyurethane (PU) breast implants were examined by two investigators in an experimental in vitro study using two high-end ultrasound devices with multi-frequency transducers (6-15 MHz, 9-16 MHz, 12.5-33 MHz).The ultrasound B-Mode was optimized using tissue harmonic imaging (THI), speckle reduction imaging (SRI, level 0-5), cross beam (high, medium, low) and photopic.Using a standardized ultrasound protocol, the implants were examined in the middle (point of highest projection) and lateral, by two independent examiners.Image evaluation was performed on anonymized digital images in the PACS. The aim was to achieve an artifact-free recording of the surface structure, the surface coating, the total image structures and, as far as possible, an artifact-free internal representation of the implants.For independent surface evaluation a score was used (0 = undetectability of surface structures, rich in artifacts, 5 = best possible, artifact free image quality). RESULTS: The quality of ultrasound imaging of breast implant surfaces after the optimization of B-Scan differed significantly comparing high-end ultrasound technology with modern high-frequency ultrasound technology (p < 0,05).The following setting has been found to be the best setting with the highest image quality:B-Mode, SRI value 3, Crossbeam high level with color coded imaging for B- mode. In the total examined frequency range of 6-33 MHz, the highest image quality was found in the average frequency range of 12.5-33 MHz at both measured points. For both devices, device 1 (high-end) and device 2 (high frequency) ultrasound, the image quality was in the12.5-33 MHz frequency range with an average image quality of 3.236. It was significantly higher, than in the lower frequency ranges and the same frequency range with THI. (p < 0,05). The image quality of the high-end sonography device was superior to the conventional high-frequency ultrasound device in all frequency ranges. CONCLUSION: High-end ultrasound imaging technology was superior in the quality of implant surface evaluation in comparison to high-frequency ultrasound sonography. The gained knowledge can serve as a basis for further multicenter clinical application and studies with the aim to develop an objective, precise tool to evaluate the implant and the surrounding tissue with ultrasound.

Creation of equal-spin triplet superconductivity at the Al/EuS interface.

In conventional superconductors, electrons of opposite spins are bound into Cooper pairs. However, when the superconductor is in contact with a non-uniformly ordered ferromagnet, an exotic type of superconductivity can appear at the interface, with electrons bound into three possible spin-triplet states. Triplet pairs with equal spin play a vital role in low-dissipation spintronics. Despite the observation of supercurrents through ferromagnets, spectroscopic evidence for the existence of equal-spin triplet pairs is still missing. Here we show a theoretical model that reveals a characteristic gap structure in the quasiparticle density of states which provides a unique signature for the presence of equal-spin triplet pairs. By scanning tunnelling spectroscopy we measure the local density of states to reveal the spin configuration of triplet pairs. We demonstrate that the Al/EuS interface causes strong and tunable spin-mixing by virtue of its spin-dependent transmission.

Signature of magnetic-dependent gapless odd frequency states at superconductor/ferromagnet interfaces.

The theory of superconductivity developed by Bardeen, Cooper and Schrieffer (BCS) explains the stabilization of electron pairs into a spin-singlet, even frequency, state by the formation of an energy gap within which the density of states is zero. At a superconductor interface with an inhomogeneous ferromagnet, a gapless odd frequency superconducting state is predicted, in which the Cooper pairs are in a spin-triplet state. Although indirect evidence for such a state has been obtained, the gap structure and pairing symmetry have not so far been determined. Here we report scanning tunnelling spectroscopy of Nb superconducting films proximity coupled to epitaxial Ho. These measurements reveal pronounced changes to the Nb subgap superconducting density of states on driving the Ho through a metamagnetic transition from a helical antiferromagnetic to a homogeneous ferromagnetic state for which a BCS-like gap is recovered. The results prove odd frequency spin-triplet superconductivity at superconductor/inhomogeneous magnet interfaces.

Seroepidemiology of leptospirosis in Minnesota wolves.

Serum samples (n = 457) from wolves (Canis lupus) in northern Minnesota were collected from 1972 through 1986 and were tested for antibodies against Leptospira interrogans using a microtiter agglutination test. Twelve serovars included in the study were: australis, autumnalis, ballum, bataviae, bratislava, canicola, copenhageni, grippotyphosa, hardjo, pomona, pyrogenes, and tarassovi. Fifty-two (11%) sera had antibody titers of greater than or equal to 1:50 against one or more serovars of L. interrogans. The seroprevalence of different serovars in decreasing order was: grippotyphosa, bratislava, autumnalis, canicola, pomona, ballum, pyrogenes, hardjo, and copenhageni. No antibodies were found against australis, bataviae, and tarassovi. These results indicate that L. interrogans infection may occur in wolves of Minnesota.

Enterobacteriaceae and Aeromonas hydrophila in Minnesota frogs and tadpoles (Rana pipiens).

In 222 Rana pipiens frogs and 34 tadpoles captured in and near Minnesota, Aeromonas hydrophila and 29 species of Enterobacteriaceae, including yersinia enterocolitica and Salmonella arizonae, were isolated from intestines. The prevalence of members of the family Enterobacteriaceae was lowest in frogs captured in early spring and highest in frogs captured in late summer.

Aeromonas hydrophila in wild-caught frogs and tadpoles (Rana pipiens) in Minnesota.

Frogs and tadpoles were captured at 14 sites in and near Minnesota during 1978-79 and nearly all appeared healthy. Aeromonas hydrophila was isolated from 94 of 294 (32%) juvenile and adult frogs and from 66 of 104 (63%) tadpoles. Of the isolates from frogs and tadpoles respectively, 68% and 47% were from the intestine only, 12% and 32% were from the intestine and the other sites, and 20% and 21% were from extraintestinal sites only. Isolations were more frequent from frogs collected in March-June than in August-November. Evidence was not found that disease due to Aeromonas hydrophila was a primary cause of declining Rana pipiens populations in Minnesota.