One-step volumetric additive manufacturing of complex polymer structures.

Two limitations of additive manufacturing methods that arise from layer-based fabrication are slow speed and geometric constraints (which include poor surface quality). Both limitations are overcome in the work reported here, introducing a new volumetric additive fabrication paradigm that produces photopolymer structures with complex nonperiodic three-dimensional geometries on a time scale of seconds. We implement this approach using holographic patterning of light fields, demonstrate the fabrication of a variety of structures, and study the properties of the light patterns and photosensitive resins required for this fabrication approach. The results indicate that low-absorbing resins containing ~0.1% photoinitiator, illuminated at modest powers (~10 to 100 mW), may be successfully used to build full structures in ~1 to 10 s

Role of heparan sulfate for attachment and entry of tick-borne encephalitis virus

AbstractAttachment of the flavivirus tick-borne encephalitis (TBE) virus to different permissive cell lines was investigated by a newly established quantitative assay using fluorescence-labeled virus. Previous work had shown that BHK-21 cell-adapted mutants of TBE virus had acquired potential heparan sulfate (HS) binding sites on the outer surface of protein E. Quantitative analysis of one of these mutants indicated that it attached to HS-expressing cell lines with a 10- to 13-fold higher affinity than wild-type TBE virus strain Neudoerfl. CHO cells deficient in HS synthesis bound less than 5% of the amount of wild-type or mutant virus that could attach to HS-containing CHO cells but were nevertheless found to be highly susceptible to infection with both viruses. Thus, even though HS is a major determinant of TBE virus attachment on HS-expressing cells, our findings suggest the existence of an alternative host cell receptor that is less abundant than HS

Exploring Human Response Times to Combinations of Audio, Haptic, and Visual Stimuli from a Mobile Device

Auditory, haptic, and visual stimuli provide alerts, notifications, and information for a wide variety of applications ranging from virtual reality to wearable and hand-held devices. Response times to these stimuli have been used to assess motor control and design human-computer interaction systems. In this study, we investigate human response times to 26 combinations of auditory, haptic, and visual stimuli at three levels (high, low, and off). We developed an iOS app that presents these stimuli in random intervals and records response times on an iPhone 11. We conducted a user study with 20 participants and found that response time decreased with more types and higher levels of stimuli. The low visual condition had the slowest mean response time (mean +/- standard deviation, 528 +/- 105 ms) and the condition with high levels of audio, haptic, and visual stimuli had the fastest mean response time (320 +/- 43 ms). This work quantifies response times to multi-modal stimuli, identifies interactions between different stimuli types and levels, and introduces an app-based method that can be widely distributed to measure response time. Understanding preferences and response times for stimuli can provide insight into designing devices for human-machine interaction.Comment: Accepted to World Haptics Conference 202

Density dependence in demography and dispersal generates fluctuating invasion speeds

Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 114 (2017): 5053-5058, doi:10.1073/pnas.1618744114.Mitigating the spread of invasive species remains difficult—substantial variability in invasion speed is increasingly well-documented, but the sources of this variability are poorly understood. We report a mechanism for invasion speed variability. The combined action of density dependence in demography and dispersal can cause invasions to fluctuate, even in constant environments. Speed fluctuations occur through creation of a pushed invasion wave that moves forward not from small populations at the leading edge but instead, from larger, more established populations that “jump” forward past the previous invasion front. Variability in strength of the push generates fluctuating invasion speeds. Conditions giving rise to fluctuations are widely documented in nature, suggesting that an important source of invasion variability may be overlooked.LLS and AKS were supported by startup funds from the University of Minnesota 348 (UMN) to AKS, BL by NSF DMS-1515875, TEXM by NSF DEB-1501814, and MGN 349 by NSF DEB-1257545 and DEB-1145017

Up the leash: Exploring canine handlers’ perceptions of volunteering in canine-assisted interventions

To date, research on university and college based canine-assisted interventions for post-secondary students have focused on identifying the effects of spending time with therapy dogs on the well-being of participants and, to a lesser extent, exploring the effects of canine-assisted interventions on therapy dogs as a means of safeguarding canine welfare. Little empirical attention has focused on understanding the experience of volunteer canine handlers – agents at the heart of the success of canine-assisted interventions. The aim of this exploratory research was to first capture the voice of these key stakeholders to better understand their experience as canine handler volunteers and second to provide preliminary insights into their well-being. Sixty volunteer handlers with varying volunteer experience with a canine therapy program at a mid-size Canadian university responded to a series of open-ended prompts related to their volunteer work and completed a battery of well-being measures. Qualitative findings revealed that most participants identified social benefits to volunteering for themselves (64%) and for their dog (55%). The perceived impact on students (33%) and the ability to help university students (36%) were the most rewarding aspects of volunteering. Though enticed to volunteer by qualities of the CAI program (36%), participant motivations to continue volunteering were predominantly associated with personal benefits of volunteering (44%). Most handlers reported no challenges associated with volunteering (73%) and described their dog as happy after sessions (71%). Participants commonly described good therapy dogs as relaxed, calm, and respectful (66%) and strong handlers as having good awareness of their dog (48%). Quantitative findings revealed volunteer handlers reported elevated levels of positive affect (p = < 0.001, d = 1.19), greater satisfaction with life (p = < 0.001, d = 0.85) and lower levels of avoidant attachment to their therapy dog (p = < 0.001, d = -1.16) when compared to normative samples. Implications for the governing of university and college based programs and handler well-being are discussed

Towards automating the sizing process in conceptual (airframe) systems architecting

Presented is a method for automated sizing of airframe systems, ultimately aiming to enable an efficient and interactive systems architecture evaluation process. The method takes as input the logical view of the system architecture. A source-sink approach combined with a Design Structure Matrix (DSM) sequencing algorithm is used to orchestrate the sequence of the sub-system sizing tasks. Bipartite graphs and a maximum matching algorithm are utilized to identify and construct the computational sizing workflows. A recursive algorithm, based on fundamental dimensions of additive physical quantities (e.g., weight, power, etc.) is employed to aggregate variables at the system level. The evaluation, based on representative test cases confirmed the correctness of the proposed method. The results also showed that the proposed approach overcomes certain limitations of existing methods and looks very promising as an initial systems architectural design enabler

Calibration of Atomic Force Microscope Tips Using Biomolecules

Atomic force microscope (AFM) images of surfaces and samples mounted on substrates are subject to artifacts such as broadening of structures and ghost images of tips due to the finite size and shape of the contacting probe. Therefore, knowledge of the radius of the AFM probe tip is essential for the interpretation of images. We have deduced the shape of the AFM tip by imaging cylindrical biological molecules of various diameters such as deoxyribonucleic acid (DNA), tobacco mosaic virus (TMV), tobacco etch virus (TEV) and bacteriophage M-13 (M-13). Using a paraboloidal tip model and numerically solving equations of contact, the curvatures of the tip and lithographically sharpened tip were ascertained