All three motional modes of a charged dielectric nanoparticle in a Paul trap are cooled by direct feedback to temperatures of a few mK. We test two methods, one based on electrical forces and the other on optical forces; for both methods, we find similar cooling efficiencies. Cooling is characterized for both feedback forces as a function of feedback parameters, background pressure, and the particle's position.
Recently, additive manufacturing (AM) by laser metal deposition (LMD) has become a key technology for fabricating highly complex parts without any support structures. Compared to the well-known powder bed fusion process, LMD enhances manufacturing possibilities to overcome AM-specific challenges such as process inherent porosity, minor build rates, and limited part size. Moreover, the advantages aforementioned combined with conventional machining enable novel manufacturing approaches in various fields of applications. Within this contribution, the additive manufacturing of filigree flexure pivots using 316L-Si by means of LMD with powder is presented. Frictionless flexure pivot bearings are used in space mechanisms that require high reliability, accuracy, and technical cleanliness. As a contribution to part qualification, the manufacturing process, powder material, and fabricated specimens were investigated in a comprehensive manner. Due to its major impact on the process, the chemical powder composition was characterized in detail by energy dispersive X-ray spectroscopy (EDX) and inductively coupled plasma optical emission spectrometry (ICP-OES). Moreover, a profound characterization of the powder morphology and flowability was carried out using scanning electron microscopy (SEM) and novel rheological investigation techniques. Furthermore, quantitative image analysis, mechanical testing, laser scanning microscopy, and 3D shape measurement of manufactured specimens were conducted. As a result, the gained knowledge was applied for the AM-specific redesign of the flexure pivot. Finally, a qualified flexure pivot has been manufactured in a hybrid manner to subsequently ensure its long-term durability in a lifetime test bench.
Deracemizations are
clearly preferable to kinetic resolutions in
the production of chiral molecules from racemates, as they allow up
to 100% chemical and optical yield. Here we present a new process
route for multienzymatic deracemizations that is relevant for reaction
systems with incompatible reaction conditions of the biocatalysts.
This often applies to combinations of lipases used for stereoselective
acylation and solvent-sensitive racemases. By encapsulating a model
racemase in polymeric vesicles, it was protected from inactivation
by the organic solvent up to phase proportions of 99%. As high yields
in the lipase reaction required either water proportions well below
1% or racemase-denaturating acyl donor concentrations, a one-pot reaction
was implemented through the sequential use of lipase and racemase-containing
nanocompartments. This strategy allowed us to perform two kinetic
resolutions with intermittent re-racemization in one pot yielding
72% (0.72 mM after 120 h) of an enantiopure product.
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