We have developed a simple method to measure the transport spin polarization of ferromagnetic materials. This technique relies on the fact that the Andreev reflection process at the interface between a superconductive and normal is influenced by the spin polarization P of the normal metal. In a very short time we have been able to measure the spin polarization of several metals: NixFe1−x, Ni, Co, Fe, NiMnSb, La0.7Sr0.3MnO3, and CrO2, whose spin polarization ranges from 35% to 90%. Our results compare well with other methods for measuring P.
The potential advantage of some magnetic sensors having a large response is greatly decreased because of the 1 / f noise. We are developing a device, the microelectromechanical system ͑MEMS͒ flux concentrator, that will mitigate the effect of this 1 / f noise. It does this by placing flux concentrators on MEMS structures that oscillate at kilohertz frequencies. By shifting the operating frequency, the 1 / f noise will be reduced by one to three orders of magnitude depending upon the sensor and the desired operating frequency. We have succeeded in fabricating the necessary MEMS structures and observing the desired kilohertz normal-mode resonant frequencies. Only microwatts are required to drive the motion. We have used spin valves for our magnetic sensors. The measured field enhancement provided by the flux concentrators agrees to within 4% with the value estimated from finite element calculations. No difference was detected in noise measurements on spin valves with and without the flux concentrators. This result provides strong evidence for the validity of our device concept. Solutions to the sole remaining fabrication problem will be discussed.
Expansion microscopy enables nanoimaging with conventional microscopes by physically and isotropically magnifying preserved biological specimens embedded in a crosslinked water-swellable hydrogel. Current expansion microscopy protocols require prior treatment with reactive anchoring chemicals to link specific labels and biomolecule classes to the gel. We describe a strategy called Magnify, which uses a mechanically sturdy gel that retains nucleic acids, proteins and lipids without the need for a separate anchoring step. Magnify expands biological specimens up to 11 times and facilitates imaging of cells and tissues with effectively around 25-nm resolution using a diffraction-limited objective lens of about 280 nm on conventional optical microscopes or with around 15 nm effective resolution if combined with super-resolution optical fluctuation imaging. We demonstrate Magnify on a broad range of biological specimens, providing insight into nanoscopic subcellular structures, including synaptic proteins from mouse brain, podocyte foot processes in formalin-fixed paraffin-embedded human kidney and defects in cilia and basal bodies in drug-treated human lung organoids.
Stimulated Raman scattering (SRS) microscopy is an emerging technology that provides high chemical specificity for endogenous biomolecules and can circumvent common constraints of fluorescence microscopy including limited capabilities to probe small biomolecules and difficulty resolving many colors simultaneously. However, the resolution of SRS microscopy remains governed by the diffraction limit. To overcome this, a new technique called molecule anchorable gel‐enabled nanoscale Imaging of Fluorescence and stimulated Raman scattering microscopy (MAGNIFIERS) that integrates SRS microscopy with expansion microscopy (ExM) is described. MAGNIFIERS offers chemical‐specific nanoscale imaging with sub‐50 nm resolution and has scalable multiplexity when combined with multiplex Raman probes and fluorescent labels. MAGNIFIERS is used to visualize nanoscale features in a label‐free manner with CH vibration of proteins, lipids, and DNA in a broad range of biological specimens, from mouse brain, liver, and kidney to human lung organoid. In addition, MAGNIFIERS is applied to track nanoscale features of protein synthesis in protein aggregates using metabolic labeling of small metabolites. Finally, MAGNIFIERS is used to demonstrate 8‐color nanoscale imaging in an expanded mouse brain section. Overall, MAGNIFIERS is a valuable platform for super‐resolution label‐free chemical imaging, high‐resolution metabolic imaging, and highly multiplexed nanoscale imaging, thus bringing SRS to nanoscopy.
The crystal structures of Zr2COl~ and HfCo7 intermetallic compounds were examined by transmission electron microscopy using both selected-area and convergent-beam electron diffraction. Results show that both have an orthorhombic crystal structure, space group Pcna. The unit cells of both compounds appear to be comprised of two long-period superlattices in antiphase relation to one another along [001].
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