This paper addresses the challenging task of optical characterization of pure, dielectric (nano-)powders with the aim to provide an end-to-end instruction from appropriate sample preparation up to the determination of material remission and absorption spectra. We succeeded in establishing an innovative preparation procedure to reproducibly obtain powder pellet samples with an ideal Lambertian scattering behavior. As a result, a procedure based on diffuse reflectance spectroscopy was developed that allows for (i) performing reproducible and artifact-free, high-quality measurements as well as (ii) a thorough optical analysis using Monte Carlo and Mie scattering simulations yielding the absorption spectrum in the visible spectral range. The procedure is valid for the particular case of powders that can be compressed into thick, non-translucent pellets and neither requires embedding of the dielectric (nano-)powders within an appropriate host matrix for measurements nor the use of integrating spheres. The reduced spectroscopic procedure minimizes the large number of sources for errors, enables an in-depth understanding of non-avoidable artifacts and is of particular advantage in the field of material sciences, i.e., for getting first insights to the optical features of a newly synthesized, pure dielectric powder, but also as an inline inspection tool for massively parallelised material characterization.

Nonlinear diffuse femtosecond-pulse reflectometry is introduced as a powerful experimental tool for the unambiguous characterization of polar and non-polar point symmetry groups of harmonic upconversion nanoparticles. Using intense ultrashort 40 femtosecond laser pulses and an appropriate figure of merit (FOM), second and third harmonic emission serve for the structural characterization of polar Yb-doped lithium niobate and non-polar titanium dioxide nanoparticles. The tool is capable of differentiating these two samples by FOM values that differ by up to 13 orders of magnitude. The general applicability to harmonic upconversion nanoparticles over a broad range of intensities and wavelength spectrum, is discussed.

In the face of a global pandemic, such as that caused by the SARS-CoV-2 virus, the prevention of new infections is essential to stop the spread and ultimately return to normality. In addition to wearing masks and maintaining safe distances, regular ventilation in enclosed spaces where several people are gathered has proven to be an effective protective measure as advised by the World Health Organization. Additionally, as has been shown in a recent study of other airborne viruses, there is a strong correlation between the CO₂level and aerosol content in a confined space under the assumption humans are the only CO₂source. This can be exploited by means of a low-cost infrared CO₂sensor to indirectly monitor the aerosol content and to provide targeted ventilation if predefined thresholds are exceeded. The distributed CO₂monitoring network presented in this paper extends that idea and provides an inexpensive, comprehensive and modular monitoring network based on readily available components and 3D printing. By using a long-range communication link (LoRa) to centrally collect the real-time CO₂concentration in a multitude of rooms, this network is particularly suitable for larger building complexes such as kindergartens, schools and universities without requiring partial or even full WLAN coverage.

Internet of Things (IoT) applications based on the single-board computer Raspberry Pi depend on reliable and sufficiently powerful energy systems to allow system diversity, flexibility, and available computing power. On this account, we developed an all-in-one module to simplify both the autonomous and network-wired power supply of Raspberry Pi-based systems. The module generates a stable voltage of 5.1 VDC with an available maximum current of 3 A to power a single Raspberry Pi model 3B+ or 4 and furthermore provides an additional power source of 3 VDC–12 VDC at a maximum of 3 A for use by arbitrary peripherals. To accommodate different use cases, the system has various energy supply options such as a 4S lithium polymer (LiPo) battery for autonomous operation, including a battery management and charging solution, as well as wire-based options, such as USB-C with USB Power Delivery (USB-PD) or Power over Ethernet (PoE+) via an additional module.

The efficacy of hyperbaric oxygen therapy in treating wound healing disorders is well established. The obvious explanation is the presence of elevated oxygen tissue tensions during the high-pressure oxygen exposure. This explanation omits that the effective agent, elevated oxygen tension, is only present for 6.25% of the time. To investigate possible prevailing vascular changes caused by HBOT, the presented device monitors the vascular response during therapy by Pulse-Transit-Time analysis. The device allows synchronous 1 kHz ECG and PPG measurements. The data are stored in a 1 GBit flash drive and retrieved post-therapy. Normoxic measurements on the authors with and without nicotine validate the device’s functionality. Measurements during HBO therapy have been successfully performed.