Space- and time-resolved Seebeck and Nernst voltages in laser-heated permalloy/gold microstructures

Thermoelectric effects in microstructured permalloy (Py) / gold (Au) wires are investigated using spatially and time-resolved measurements based on scanning focused laser heating. Supported by numerical simulations of the temperature distribution, we identify two major contributions to the laser-induced signals: (i) the Seebeck effect due to thermocouples of Py/Au and (ii) the anomalous Nernst effect (ANE) in Py with a coefficient of NANE 0:5 V/K. ANE-based magnetic imaging of magnetic domains and magnetization reversal is demonstrated with a lateral resolution on the m-scale

High performance WR-1.5 corrugated horn based on stacked rings

We present the development and characterisation of a high frequency (500-750 GHz) corrugated horn based on stacked rings. A previous horn design, based on a Winston profile, has been adapted for the purpose of this manufacturing process without noticeable RF degradation. A subset of experimental results obtained using a vector network analyser are presented and compared to the predicted performance. These first results demonstrate that this technology is suitable for most commercial applications and also astronomical receivers in need of horn arrays at high frequencies.Comment: 9 page

Development of the new long trace profilometer at LCLS for bendable x-ray mirror metrology

The Linac Coherent Light Source (LCLS) is undergoing an upgrade to a double source setup to provide eight experimental hutches (five existing and three new) with either high-repetition or high-intensity pulses and highly coherent X-ray beams. The photon transportation and distribution to each hutch relies on, among other elements, bendable mirrors. Given the coherence of the LCLS source, and to avoid introducing wavefront distortions beyond workable limits, the mirrors need to have extremely smooth surfaces, with a figure compliant with the nominal profile (usually elliptical). The effectiveness and the accuracy of the bending system and of the actuators over the entire length of the mirror (up to 1.2 m) need to be assessed by an appropriate metrology system. Long Trace Profilometry (LTP) is a suitable technique to characterize a slightly-curved surface mirror profile with very high sensitivity, provided that the optomechanical system implementation enables sensitivity and accuracy values compatible with the mentioned surface quality requirements. In this paper, we show the status and performance of the LTP under development at LCLS. The LTP essentially consists of an advanced optical head that endows a laser beam with sharp interferential features to increase its resolution and detects the optical lever of the beam reflected by the sample, plus a high-precision gantry system (Q-Sys) for accurate scanning of the mirror under test, under impact of its bending mechanics and cooling system. The measured results are compared to the simulated performance of the LTP, and we show the way of the oncoming improvement of the instrument

Immune Antibodies and Helminth Products Drive CXCR2-Dependent Macrophage-Myofibroblast Crosstalk to Promote Intestinal Repair.

Helminth parasites can cause considerable damage when migrating through host tissues, thus making rapid tissue repair imperative to prevent bleeding and bacterial dissemination particularly during enteric infection. However, how protective type 2 responses targeted against these tissue-disruptive multicellular parasites might contribute to homeostatic wound healing in the intestine has remained unclear. Here, we observed that mice lacking antibodies (Aid-/-) or activating Fc receptors (Fcrg-/-) displayed impaired intestinal repair following infection with the murine helminth Heligmosomoides polygyrus bakeri (Hpb), whilst transfer of immune serum could partially restore chemokine production and rescue wound healing in Aid-/- mice. Impaired healing was associated with a reduced expression of CXCR2 ligands (CXCL2/3) by macrophages (MΦ) and myofibroblasts (MF) within intestinal lesions. Whilst antibodies and helminths together triggered CXCL2 production by MΦ in vitro via surface FcR engagement, chemokine secretion by intestinal MF was elicited by helminths directly via Fcrg-chain/dectin2 signaling. Blockade of CXCR2 during Hpb challenge infection reproduced the delayed wound repair observed in helminth infected Aid-/- and Fcrg-/- mice. Finally, conditioned media from human MΦ stimulated with infective larvae of the helminth Ascaris suum together with immune serum, promoted CXCR2-dependent scratch wound closure by human MF in vitro. Collectively our findings suggest that helminths and antibodies instruct a chemokine driven MΦ-MF crosstalk to promote intestinal repair, a capacity that may be harnessed in clinical settings of impaired wound healing

Phase imaging with intermodulation atomic force microscopy

Intermodulation atomic force microscopy (IMAFM) is a dynamic mode of atomic force microscopy (AFM) with two-tone excitation. The oscillating AFM cantilever in close proximity to a surface experiences the nonlinear tip-sample force which mixes the drive tones and generates new frequency components in the cantilever response known as intermodulation products (IMPs). We present a procedure for extracting the phase at each IMP and demonstrate phase images made by recording this phase while scanning. Amplitude and phase images at intermodulation frequencies exhibit enhanced topographic and material contrast.Comment: 6 pages, 6 page

Monolithic Metal-Coated Plastic Components for mm-Wave Applications

A stereolithography-based manufacturing process for monolithic high aspect ratio components for mm-wave and sub-mm-wave applications is demonstrated. A 25mm long straight waveguide and a diagonal horn antenna, both for the WR-3.4 band (220–330 GHz), are manufactured and characterized. The waveguide is found to exhibit transmission losses close to the theoretical minimum for Cu, and the performance of the diagonal antenna in terms of cross-polarization and directivity matches closely a metallic split-block reference antenna. These results confirm the high surface quality and mechanical accuracy of the employed 3D printing and plating techniques and thus validate the process for rapid manufacturing of monolithic components up to 330 GHz

Wavefront preserving optics for diffraction-limited storage rings and free-electron lasers

With the advent of Diffraction Limited Storage Rings (DLSR) and the Free Electron Lasers (FEL), the challenge for optical designers is to achieve diffraction-limited spot in the experimental chamber preserving the wavefront. This improvement permits working out of focus with almost uniform beam. To reach this level of quality on the beam, one should go behind the Marechal Criterion, stating that a Strehl Ratio (SR, e.g. the ratio between the intensity on the spot for a perfect optical system and the actual one) of 0.8 is a synonymous of a well performing optic system. In reality, a Strehl ratio in excess of 0.95 is needed for wavefront preserving purposes. This corresponds having long mirrors polished at a precision of better than 1 nm rms. With the initial upgrade of the photon transport system of LCLS we demonstrated that it is possible to have an “almost” perfect beam out of focus putting proper attention to all the details and, aiming for a SR of 0.97. But, besides the high precision shape error, some other details shall be considered. For instance, how many beam sigma one should consider for the specifying his mirror and, also, does the slope errors play any role in the quality of the beam out of focus? Moreover, with the advent of SXR DLSRs, it’s important to understand the requirements for the gratings, behind the shape and slope errors, e.g. on the precision of the groove placement. Also, in this case, the Strehl Ratio is a good way for assessing this problem