Many people have flipped coins but few have stopped to ponder the statistical and physical intricacies of the process. In a preregistered study we collected \(350{,}757\) coin flips to test the ...counterintuitive prediction from a physics model of human coin tossing developed by Diaconis, Holmes, and Montgomery (DHM; 2007). The model asserts that when people flip an ordinary coin, it tends to land on the same side it started -- DHM estimated the probability of a same-side outcome to be about 51%. Our data lend strong support to this precise prediction: the coins landed on the same side more often than not, \(\text{Pr}(\text{same side}) = 0.508\), 95% credible interval (CI) \(0.506\), \(0.509\), \(\text{BF}_{\text{same-side bias}} = 2359\). Furthermore, the data revealed considerable between-people variation in the degree of this same-side bias. Our data also confirmed the generic prediction that when people flip an ordinary coin -- with the initial side-up randomly determined -- it is equally likely to land heads or tails: \(\text{Pr}(\text{heads}) = 0.500\), 95% CI \(0.498\), \(0.502\), \(\text{BF}_{\text{heads-tails bias}} = 0.182\). Furthermore, this lack of heads-tails bias does not appear to vary across coins. Additional exploratory analyses revealed that the within-people same-side bias decreased as more coins were flipped, an effect that is consistent with the possibility that practice makes people flip coins in a less wobbly fashion. Our data therefore provide strong evidence that when some (but not all) people flip a fair coin, it tends to land on the same side it started. Our data provide compelling statistical support for the DHM physics model of coin tossing.
Changes in Curriculum Learning Goals van Ooijen-van der Linden, Linda; Roblin, Natalie; Nak, Jason ...
Creating the Desire for Change in Higher Education,
2023
Book Chapter
Microfluidic scaffolds for tissue engineering Bonassar, Lawrence J; Stroock, Abraham D; Choi, Nak Won ...
Nature materials,
200711, 2007-Nov, 20071101, Letnik:
6, Številka:
11
Journal Article
Recenzirano
Most methods to culture cells in three dimensions depend on a cell-seedable biomaterial to define the global structure of the culture and the microenvironment of the cells. Efforts to tailor these ...scaffolds have focused on the chemical and mechanical properties of the biomaterial itself. Here, we present a strategy to control the distributions of soluble chemicals within the scaffold with convective mass transfer via microfluidic networks embedded directly within the cell-seeded biomaterial. Our presentation of this strategy includes: a lithographic technique to build functional microfluidic structures within a calcium alginate hydrogel seeded with cells; characterization of this process with respect to microstructural fidelity and cell viability; characterization of convective and diffusive mass transfer of small and large solutes within this microfluidic scaffold; and demonstration of temporal and spatial control of the distribution of non-reactive solutes and reactive solutes (that is, metabolites) within the bulk of the scaffold. This approach to control the chemical environment on a micrometre scale within a macroscopic scaffold could aid in engineering complex tissues.
A Microfluidic Biomaterial Cabodi, Mario; Choi, Nak Won; Gleghorn, Jason P ...
Journal of the American Chemical Society,
10/2005, Letnik:
127, Številka:
40
Journal Article
Recenzirano
We report on the incorporation of microfluidic structure within a high-water-content hydrogel 4% (w/v) calcium alginate. We used the microfluidic network to control the chemical environment within ...the hydrogel and demonstrated higher rates of delivery and extraction of solutes than was achievable by diffusion alone.
Abstract Motivated by the necessity to engineer appropriately stratified cartilage, the shear mechanics of layered, bovine chondrocyte-seeded 20 mg/mL alginate scaffolds were investigated and related ...to the structure and biochemical composition. Chondrocyte-seeded alginate scaffolds were exposed to a calcium-chelating solution, layered, crosslinked in CaCl2 , and cultured for 10 weeks. The shear mechanical properties of the layered gels were statistically similar to those of the non-layered controls. Shear modulus of layered gels increased by approximately six-fold while toughness and shear strength increased by more than two-fold during the culture period. Hydroxyproline content in both layered gels and controls had statistically significant increases after 6 weeks. Glycosaminoglycan (GAG) content of controls increased throughout culture while GAG content in layered gels leveled off after 4 weeks. Hematoxylin and eosin histological staining showed tissue growth at the interface over the first 4 weeks. Shear mechanical properties in the engineered tissues showed significant correlations to hydroxyproline content. Dependence of interfacial mechanical properties on hydroxyproline content was most evident for layered gels when compared to controls, especially for toughness and shear strength. Additionally, interfacial properties showed almost no dependence on GAG content. These findings demonstrate the feasibility of creating stratified engineered tissues through layering and that collagen deposition is necessary for interfacial integrity.
Abstract Tissue templates for reconstruction and regeneration in vivo have achieved clinical successes for homogeneous tissues in well vascularized regions. Outstanding challenges exist for ...applications in poorly vascularized regions and for spatially differentiated tissues. Here, we present a strategy to control the spatial patterns of cell and vascular ingrowth throughout the volume of a bioremodelable and resorbable matrix via well-defined micropores and networks of microchannels. Our presentation of this approach includes: a description of a lithographic technique to form deterministic microstructures within a matrix of native collagen; elucidation of multistep process by which microstructures drive rapid invasion and vascularization; and demonstration of long range guidance of invasion through the full thickness of patterned templates. Experiments were performed in a murine wound model. These microstructured tissue templates (MTTs) could improve outcomes in reconstructive surgery and open paths to directed regeneration of spatially heterogeneous tissues or organs.
Cardiac involvement associated with multi-system inflammatory syndrome in children has been extensively reported, but the prevalence of cardiac involvement in children with SARS-CoV-2 infection in ...the absence of inflammatory syndrome has not been well described. In this retrospective, single centre, cohort study, we describe the cardiac involvement found in this population and report on outcomes of patients with and without elevated cardiac biomarkers. Those with multi-system inflammatory syndrome in children, cardiomyopathy, or complex CHD were excluded. Inclusion criteriaz were met by 80 patients during the initial peak of the pandemic at our institution. High-sensitivity troponin T and/or N-terminal pro-brain type natriuretic peptide were measured in 27/80 (34%) patients and abnormalities were present in 5/27 (19%), all of whom had underlying comorbidities. Advanced respiratory support was required in all patients with elevated cardiac biomarkers. Electrocardiographic abnormalities were identified in 14/38 (37%) studies. Echocardiograms were performed on 7/80 patients, and none demonstrated left ventricular dysfunction. Larger studies to determine the true extent of cardiac involvement in children with COVID-19 would be useful to guide recommendations for standard workup and management.
The study of quality of life (QOL) in patients with asymptomatic diseases receiving interventional treatment provides an essential metric for the assessment of procedural benefits in the surgical ...patient population. In this study, we analyzed QOL data collected from patients with unruptured intracranial aneurysms (UIAs) before and after endovascular coiling in the HEAT Trial, alongside a systematic review on QOL in unruptured brain aneurysms.
HEAT was a randomized controlled trial comparing recurrence rates in aneurysms treated with either bare platinum coils or hydrogel coils. Patients enrolled in this trial completed a short form−36 (SF-36) QOL questionnaire before treatment and at the 3- to 12- and 18- to 24-month follow-ups. The change in QOL before and after treatment was assessed. Regression analysis evaluated the effect of select baseline characteristics on QOL change.
A total of 270 patients were eligible for analysis. There was an increase in the role physical (P = 0.043), vitality (P = 0.022), and emotional well-being (P < 0.001) QOL components at the 18- to 24-month follow-up compared with baseline scores. Regression analysis showed that age younger than 60 and absence of serious adverse events were associated with improved social functioning and vitality. The literature review showed a mixed effect of intervention on QOL in patients with UIAs.
Our analysis has revealed that patients with 3- to 14-mm UIAs had improvements in some physical and emotional components of QOL at 18–24 months following aneurysm coiling in the HEAT study. The literature remains indeterminate on this issue. Further studies are needed to better understand the effects of the diagnosis of UIAs and their treatment on QOL.
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