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Abstract: Solid state particle detectors are based on converting the energy of the particle into charge which forms a pulse. The pulse height defect (PHD) can be described as the deviation from the ideal 100% energy-charge conversion and it is a function of the type and energy of the detected particles, thus being a major cause of non-linearities in the energy response curves of the detectors. Accounting for PHD is essential when analysing energy spectra from heavier ions and/or at low energies, where the relative importance of the corrections is larger. Two major contributions to the PHD are considered in this work: the effect of the detector dead layer and the non-ionising collisions taking place in the active area of the detector. The first one can be easily taken into account if the dead layer is well-characterized. For the second contribution, a very simple yet effective ad-hoc model is discussed. This model, which requires no significant computational effort, allows calculation of the non-ionising energy losses for every ion and for a wide energy range. The importance of these corrections is stressed by showing real case examples of analysis where the PHD is significant. The methods described have been implemented in the DataFurnace code, allowing the user to routinely correct for PHD when analysing data from Rutherford backscattering spectrometry or energy recoil detection analysis. [Copyright &y& Elsevier]

Abstract: The stopping forces (a.k.a. stopping powers) for 4He, 12C, 16O, 27Al and 28Si ions in alumina (Al2O3) have been experimentally determined in the energy range of 40–1250keV/nucleon. Two independent analysis methods based on Simulated Annealing and Bayesian Inference techniques (as implemented in the Hotstop and Data Furnace codes) have been used to extract the continuous stopping curves from sets of backscattering spectra. Bayesian analysis has been found to be very adequate for providing systematic estimations of the confidence level for the results. The results of both methods are reported and compared with other available data. [Copyright &y& Elsevier]

The stopping power of SiO2 for 200 keV–3 MeV He ions has been evaluated by Rutherford backscattering (RBS) and a semiempirical stopping power curve is proposed in this energy range. The curve is parameterized using the Andersen and Ziegler’s formula, allowing for an easy implementation in any simulation program. The estimated accuracy of the present stopping power curve is of the order of 2%. Samples used for the measurements consist of thin SiO2 films grown by wet thermal oxidation of Si(1 0 0) wafers. The thickness of each sample was independently determined by reflectance spectroscopy. The fitting of the experimental RBS spectra was performed using full Monte Carlo calculation of trajectories in the binary collision approximation. [Copyright &y& Elsevier]

Although usually complex to handle, nanomechanical sensors are exceptional, label-free tools for monitoring molecular conformational changes, which makes them of paramount importance in understanding biomolecular interactions. Herein, a simple and inexpensive mechanical imaging approach based on low-stiffness cantilevers with structural coloration (mechanochromic cantilevers (MMC)) is demonstrated, able to monitor and quantify molecular conformational changes with similar sensitivity to the classical optical beam detection method of cantilever-based sensors (≈4.6 × 10 -3  N m -1 ). This high sensitivity is achieved by using a white light and an RGB camera working in the reflection configuration. The sensor performance is demonstrated by monitoring the UV-light induced reversible conformational changes of azobenzene molecules coating. The trans-cis isomerization of the azobenzene molecules induces a deflection of the cantilevers modifying their diffracted color, which returns to the initial state by cis-trans relaxation. Interestingly, the mechanical imaging enables a simultaneous 2D mapping of the response thus enhancing the spatial resolution of the measurements. A tight correlation is found between the color output and the cantilever's deflection and curvature angle (sensitivities of 5 × 10 -3  Hue µm -1 and 1.5 × 10 -1  Hue (°) -1 ). These findings highlight the suitability of low-stiffness MMC as an enabling technology for monitoring molecular changes with unprecedented simplicity, high-throughput capability, and functionalities., (© 2021 Wiley-VCH GmbH.)

New multi-stimuli responsive materials are required in smart systems applications to overcome current limitations in remote actuation and to achieve versatile operation in inaccessible environments. The incorporation of detection mechanisms to quantify in real time the response to external stimuli is crucial for the development of automated systems. Here, we present the first wireless opto-magnetic actuator with mechanochromic response. The device, based on a nanostructured-iron (Fe) layer transferred onto suspended elastomer structures with a periodically corrugated backside, can be actuated both optically (in a broadband spectral range) and magnetically. The combined opto-magnetic stimulus can accurately modulate the mechanical response (strength and direction) of the device. The structural coloration generated at the corrugated back surface enables to easily map and quantify, in 2D, the mechanical deflections by analyzing in real time the hue changes of images taken using a conventional RGB smartphone camera, with a precision of 0.05°. We demonstrate the independent and synergetic optical and magnetic actuation and detection with a detection limit of 1.8 mW·cm -2 and 0.34 mT, respectively. The simple operation, versatility, and cost-effectiveness of the wireless multiactuated device with highly sensitive mechanochromic mapping paves the way to a new generation of wirelessly controlled smart systems.

The addition of compounds to scavenge the radical species produced during biological small-angle X-ray scattering (BioSAXS) experiments is a common strategy to reduce the effects of radiation damage and produce better quality data. As almost half of the experiments leading to structures deposited in the SASBDB database used scavengers, finding potent scavengers would be advantageous for many experiments. Here, four compounds, three nucleosides and one nitrogenous base, are presented which can act as very effective radical-scavenging additives and increase the critical dose by up to 20 times without altering the stability or reducing the contrast of the tested protein solutions. The efficacy of these scavengers is higher than those commonly used in the field to date, as verified for lysozyme solutions at various concentrations from 7.0 to 0.5 mg ml -1 . The compounds are also very efficient at mitigating radiation damage to four proteins with molecular weights ranging from 7 to 240 kDa and pH values from 3 to 8, with the extreme case being catalase at 6.7 mg ml -1 , with a scavenging factor exceeding 100. These scavengers can therefore be instrumental in expanding BioSAXS to low-molecular-weight and low-concentration protein samples that were previously inaccessible owing to poor data quality. It is also demonstrated that an increase in the critical dose in standard BioSAXS experiments leads to an increment in the retrieved information, in particular at higher angles, and thus to higher resolution of the model.

Positron annihilation lifetime spectroscopy (PALS) has potential as a novel rapid characterization method for self-assembly amphiphile systems; however, a lack of systematic correlation of PALS parameters with structural attributes has limited its more widespread application. In this study, using the well-characterized phytantriol/water and the phytantriol/vitamin E acetate/water self-assembly amphiphile systems, the impact of systematic structural changes controlled by changes in composition and temperature on PALS parameters has been studied. The PALS parameters (orthopositronium (oPs) lifetime and intensity signatures) were shown to be sensitive to the molecular packing and mobility of the self-assembled lipid molecules in various lyotropic liquid crystalline phases, enabling differentiation between liquid crystalline structures. The oPs lifetime, related to the molecular packing and mobility, is correlated with rheological properties of the individual mesophases. The oPs lifetime links the lipid chain packing and mobility in the various mesophases to resultant macroscopic properties, such as permeability, which is critical for the use of these mesophase structures as diffusion-controlled release matrices for active liposoluble compounds.