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Text input is desirable across various eXtended Reality (XR) use cases and is particularly crucial for knowledge and office work. This article compares handwriting text input between Virtual Reality (VR) and Video See-Through Augmented Reality (VST AR), facilitated by physically aligned and mid-air surfaces when writing simple and complex sentences. In a $2\times 2\times 2$ experimental design, 72 participants performed two ten-minute handwriting sessions, each including ten simple and ten complex sentences representing text input in real-world scenarios. Our developed handwriting application supports different XR displays, surface alignments, and handwriting recognition based on digital ink. We evaluated usability, user experience, task load, text input performance, and handwriting style. Our results indicate high usability with a successful transfer of handwriting skills to the virtual domain. XR displays and surface alignments did not impact text input speed and error rate. However, sentence complexities did, with participants achieving higher input speeds and fewer errors for simple sentences (17.85 WPM, 0.51% MSD ER) than complex sentences (15.07 WPM, 1.74% MSD ER). Handwriting on physically aligned surfaces showed higher learnability and lower physical demand, making them more suitable for prolonged handwriting sessions. Handwriting on mid-air surfaces yielded higher novelty and stimulation ratings, which might diminish with more experience. Surface alignments and sentence complexities significantly affected handwriting style, leading to enlarged and more connected cursive writing in both mid-air and for simple sentences. The study also demonstrated the benefits of using XR controllers in a pen-like posture to mimic styluses and pressure-sensitive tips on physical surfaces for input detection. We additionally provide a phrase set of simple and complex sentences as a basis for future text input studies, which can be expanded and adapted.
RESUMO
The analysis of antigen-specific T-cell responses has become routine in many laboratories. Functional T-cell assays like enzyme-linked-immuno-spot (ELISPOT), which depend on antigen-specific stimulation, increasingly use peptides to represent the antigen of interest. Besides single peptides, mixtures of peptides (peptide pools) are very frequently applied. Such peptide pools may, for example, represent entire proteins (with overlapping peptides covering a protein sequence) or include noncontiguous peptides such as a collection of T-cell-stimulating peptides. The optimum specification of single peptides or peptide pools for T-cell stimulation assays will depend on the purpose of the test, the target T-cell population, the availability of sample, requirements regarding reproducibility, and, last but not least, the available budget, to mention only the most important factors. Because of the way peptides are produced, they will always contain certain amounts of impurities such as peptides with deletions or truncated peptides, and there may be additional by-products of peptide synthesis. Optimized synthesis protocols as well as purification help reduce impurities that might otherwise cause false-positive assay results. However, specific requirements with respect to purity will vary depending on the purpose of an assay. Finally, storage conditions significantly affect the shelf life of peptides, which is relevant especially for longitudinal studies. The present book chapter addresses all of these aspects in detail. It should provide the researcher with all necessary background knowledge for making the right decisions when it comes to choosing, using, and storing peptides for ELISPOT and other T-cell stimulation assays.