Design principles for flexible protection inspired by ancient fish armor of Polypteridae

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 98-101).This thesis is about designing structures that combine the dual functions of mechanical protection and flexibility of motion. The structures are inspired by principles observed in the ganoid squamation (scale assembly) of an ancient fish species called Polypteridae, which first appeared 96 million years ago. Prior work on Polypteridae has focused on understanding the role of the inherent material properties (e.g., stiffness, strength, etc.) of the individual bony scales to provide penetration resistance. Here, geometric design is explored at increasingly larger length scales including 1) morphometric features within individual scales, 2) morphometry of the individual scales as a whole, 3) scale-to-scale interconnections and anisotropic ranges of motion, and, lastly, 4) the entire assembled scale squamation and anisotropic ranges of motion of the entire fish body. Experimental, computational, and mathematical methods employed were micro-computed tomography, microscopy, morphometric analysis, and three-dimensional printing of prototypes. The geometrical design principles discovered were related to biomechanical mobility and protection and then implemented into a generalized, functional design system which possesses similar anisotropic distinctive degrees of freedom and ranges of motion as Polypteridae. The design system offers potential for applications in fields of transportation, military, and architecture.by Steffen H. Reichert.S.M

Patterns of alcohol consumption among individuals with alcohol use disorder during the COVID-19 pandemic and lockdowns in Germany

Objective: To examine whether lockdown measures are associated with AC and consumption-related temporal and psychological within-person mechanisms. Design, setting, and participants: This quantitative, intensive, longitudinal cohort study recruited 1743 participants from 3 sites from February 20, 2020, to February 28, 2021. Data were provided before and within the second lockdown of the COVID-19 pandemic in Germany: before lockdown (October 2 to November 1, 2020); light lockdown (November 2 to December 15, 2020); and hard lockdown (December 16, 2020, to February 28, 2021). Main outcomes and measures: Daily ratings of AC (main outcome) captured during 3 lockdown phases (main variable) and temporal (weekends and holidays) and psychological (social isolation and drinking intention) correlates. Results: Of the 1743 screened participants, 189 (119 [63.0%] male; median [IQR] age, 37 [27.5-52.0] years) with at least 2 alcohol use disorder (AUD) criteria according to the Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) yet without the need for medically supervised alcohol withdrawal were included. These individuals provided 14 694 smartphone ratings from October 2020 through February 2021. Multilevel modeling revealed significantly higher AC (grams of alcohol per day) on weekend days vs weekdays (β = 11.39; 95% CI, 10.00-12.77; P < .001). Alcohol consumption was above the overall average on Christmas (β = 26.82; 95% CI, 21.87-31.77; P < .001) and New Year's Eve (β = 66.88; 95% CI, 59.22-74.54; P < .001). During the hard lockdown, perceived social isolation was significantly higher (β = 0.12; 95% CI, 0.06-0.15; P < .001), but AC was significantly lower (β = -5.45; 95% CI, -8.00 to -2.90; P = .001). Independent of lockdown, intention to drink less alcohol was associated with lower AC (β = -11.10; 95% CI, -13.63 to -8.58; P < .001). Notably, differences in AC between weekend and weekdays decreased both during the hard lockdown (β = -6.14; 95% CI, -9.96 to -2.31; P = .002) and in participants with severe AUD (β = -6.26; 95% CI, -10.18 to -2.34; P = .002). Conclusions and relevance: This 5-month cohort study found no immediate negative associations of lockdown measures with overall AC. Rather, weekend-weekday and holiday AC patterns exceeded lockdown effects. Differences in AC between weekend days and weekdays evinced that weekend drinking cycles decreased as a function of AUD severity and lockdown measures, indicating a potential mechanism of losing and regaining control. This finding suggests that temporal patterns and drinking intention constitute promising targets for prevention and intervention, even in high-risk individuals