Mass
spectrometry imaging is a technique uniquely suited to localize
and identify lipids in a tissue sample. Using an atmospheric pressure
(AP-) matrix-assisted laser desorption ionization (MALDI) source coupled
to an Orbitrap Elite, numerous lipid locations and structures can
be determined in high mass resolution spectra and at cellular spatial
resolution, but careful sample preparation is necessary. We tested
11 protocols on serial brain sections for the commonly used MALDI
matrices CHCA, norharmane, DHB, DHAP, THAP, and DAN in combination
with tissue washing and matrix additives to determine the lipid coverage,
signal intensity, and spatial resolution achievable with AP-MALDI.
In positive-ion mode, the most lipids could be detected with CHCA
and THAP, while THAP and DAN without additional treatment offered
the best signal intensities. In negative-ion mode, DAN showed the
best lipid coverage and DHAP performed superiorly for gangliosides.
DHB produced intense cholesterol signals in the white matter. One
hundred fifty-five lipids were assigned in positive-ion mode (THAP)
and 137 in negative-ion mode (DAN), and 76 peaks were identified using
on-tissue tandem-MS. The spatial resolution achievable with DAN was
10 μm, confirmed with on tissue line-scans. This enabled the
association of lipid species to single neurons in AP-MALDI images.
The results show that the performance of AP-MALDI is comparable to
vacuum MALDI techniques for lipid imaging.
Aluminum-copper (Al-Cu) interconnects are of great interest for a variety of electrical applications, such as lithium-ion batteries. In this paper, the effects of thermal and electrical aging on the intermetallic compound growth of laser braze-welded Al-Cu interconnects are reported. Thermal aging was studied in a temperature range from 200 to 500 °C for durations between 1 and 120 h. Electrical aging was studied with 200 A direct current application with different polarities and durations between 1 and 24 h. The formation of intermetallic compounds was found to be dependent on the type of aging and, for electrical aging, on the polarity of the current. The growth of intermetallic compounds under the influence of the electric current was distinctly higher than for thermal annealing conditions. The formation of voids at the transition between intermetallic compounds indicates that electromigration may be the main driving force for the accelerated intermetallic growth.
Transparent Haptics
Effectiveness of inkjet printing of piezoelectric thin films for haptic devices is demonstrated in article number 2200147 by Sebastjan Glinsek and co‐workers. A transparent device, based on printed piezoelectric lead zirconate titanate and interdigitated indium tin oxide electrodes, exhibits a standing Lamb wave at 63.3 kHz. At an applied voltage of 100 V, the out‐of‐plane displacement reaches 2 μm, which creates a friction modulation functionality.
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