Simulation of phase behavior in lipid bilayers, vesicles, and wrapped nanoparticles

Lipids, specifically phospholipids like dipalmitoylphosphatidylcholine (DPPC), undergo an order/disorder phase transition between fluid and gel states at ambient temperature and pressure. In the case of lipid-wrapped nanoparticles (LNP), where lipids are wrapped around a nanoparticle core, additional factors like curvature and nano-lipid interaction are present, resulting in a relatively poor understanding of the transition. Computer simulation, specifically molecular dynamics, is an ideal technique to study the fluid/gel transition from the molecular viewpoint. However, simulation of phase transitions is difficult; large free energy barriers separate stable phases, leading to broken ergodicity. Enhanced sampling methods are necessary to study rare events, like phase transitions, which occur on the second, or longer, timescale. Two such methods, the generalized replica exchange method (gREM) and statistical temperature molecular dynamics (STMD), and their recent developments, utilize generalized ensembles to provide enhanced sampling near phase transitions. Using the above methods,we studied flat lamellar bilayers, followed by more complex curved vesicles, and ultimately LNP. In bilayers, the gREM finds a strong coupling between phase transitions of the lipid and water subsystems. Subsequent simulations on an implicit water bilayer revealed distinct subphase transitions between coexisting states of fluid and gel lipids. STMD applied to vesicles shows weakening of the transition and overall lowering of the transition temperature with decreasing diameter, from first order at 40 nm to borderline first/second order at 20 nm and 10 nm. No homogeneous gel phase is formed, instead, low energy structures exhibit a faceted gel phase with gel patches separated by fluid lipid seams. For LNP, we find that curvature promotes the fluid phase but the presence of a core induces order, particularly in the inner layer. This nontrivial balance results in a broad, continuous phase transition for small LNP that becomes a sharp, first order transition between distinct fluid and gel states for large LNP. Overall, LNP hold great promise in a wide range of fields like drug delivery, imaging, and photocatalysis. We aim to provide a first-principles understanding of their properties by utilizing innovative simulation methods to obtain molecular details not available to experimental or traditional methods

Scholars and Literati at the University of Leiden (1575–1800)

This note is a summary description of the set of scholars and literati who taught at the University of Leiden from its inception in 1575 to the eve of the Industrial Revolution (1800)

Scholars and Literati at the University of Leipzig (1409–1800)

This note is a summary description of the set of scholars and literati who taught at the University of Leipzig from its inception in 1409 to the eve of the Industrial Revolution (1800)

Scholars and Literati at the University of Jena (1558–1800)

This note is a summary description of the set of scholars and literati who taught at the University of Jena from its inception in 1558 to the eve of the Industrial Revolution (1800)

Scholars and Literati at the University of Göttingen (1734–1800)

This note is a summary description of the set of scholars and literati who taught at the University of Göttingen from its inception in 1734 to the eve of the Industrial Revolution (1800). &nbsp

Scholars and Literati at the University of Gießen (1607–1800)

This note is a summary description of the set of scholars and literati who taught at the University of Gießen from its inception in 1607 to the eve of the Industrial Revolution (1800)

Leaders and laggards in life expectancy among European scholars from the sixteenth to the early twentieth century

When did mortality first start to decline, and among whom? We build a large, new data set with more than 30,000 scholars covering the sixteenth to the early twentieth century to analyze the timing of the mortality decline and the heterogeneity in life expectancy gains among scholars in the Holy Roman Empire. The large sample size, well-defined entry into the risk group, and heterogeneity in social status are among the key advantages of the new database. After recovering from a severe mortality crisis in the seventeenth century, life expectancy among scholars started to increase as early as in the eighteenth century, well before the Industrial Revolution. Our finding that members of scientific academies-an elite group among scholars-were the first to experience mortality improvements suggests that 300 years ago, individuals with higher social status already enjoyed lower mortality. We also show, however, that the onset of mortality improvements among scholars in medicine was delayed, possibly because these scholars were exposed to pathogens and did not have germ theory knowledge that might have protected them. The disadvantage among medical professionals decreased toward the end of the nineteenth century. Our results provide a new perspective on the historical timing of mortality improvements, and the database accompanying our study facilitates replication and extensions.Peer reviewe

The Academic Market and the Rise of Universities in Medieval and Early Modern Europe (1000-1800)

We argue that market forces shaped the geographic distribution of upper-tail human capital across Europe during the Middle Ages, and contributed to bolstering universities at the dawn of the Humanistic and Scientific Revolutions. We build a unique database of thousands of scholars from university sources covering all of Europe, construct an index of their ability, and map the academic market in the medieval and early modern periods. We show that scholars tended to concentrate in the best universities (agglomeration), that better scholars were more sensitive to the quality of the university (positive sorting) and migrated over greater distances (positive selection). Agglomeration, selection and sorting patterns testify to an integrated academic market, made possible by the use of a common language (Latin)

Are Scholars’ Wages Correlated with their Human Capital?

Throughout our project on premodern academia, we use a heuristic human capital index to measure each scholar’s quality. This index is built by combining several statistics from individual Wikipedia and Worldcat pages. The question we address here is whether this measure is correlated with the actual wages professors received. This note is a technical appendix to our paper on the academic market (De la Croix et al. 2020) but also has an interest as a stand-alone publication. There is considerable evidence that compensations for academic contractswentwell beyond paid salaries.1 They included payments from students, prebends,2 and many forms of in-kind benefits. Yet, it is interesting to examine the relationship between scholars’ human capital and existing data on monetary remunerations. Such remunerations have been used by Dittmar (2019) to show that professor salaries increased significantly relative to skilled wages after printing spread, with science professors benefiting from the largest salary increases. In the two sections below, we first review the available data on salaries, and argue that such data are imperfect proxies for the overall remuneration for academic services (i.e. a scholar’s market value). Keeping in mind such limitations, we thendocument a positive correlation between monetary income and scholars’ human capital.&nbsp

Integrating technology and social media into introductory chemistry courses to create inclusive, informed, and engaged citizenry

The introductory chemistry courses are often viewed as gatekeeping courses that explicitly or implicitly select the born to be scientists or engineers, instead of gateway courses for world citizens, who can appreciate chemistry as an essential aspect of their everyday lives, regardless of their future careers of choice. Students enter these courses with widely varying backgrounds that impact their level of prior content knowledge, skillsets, engagement in the material, as well as intellectual and emotional maturity. Often courses are taught in large classrooms, with an eclectic presentation of dense course content, broadening the already significant gap between what students perceive as classroom curriculum and the knowledge and skillset they need to tackle real societal issues. In our modern world, diverse members of the society are required to work collaboratively to generate and implement multidisciplinary solutions to address global problems. Hence, it is crucial that all educators involved in teaching these introductory courses go the extra mile to create opportunities for all students to feel, "This material is important to know, I can understand it, and I can apply it to concerns/topics in my daily life". At present, we are entrusted with the exciting task and great challenge of educating the Post-millennials also known as iGens, who were born into a world of internet and hence have been comfortable with technology and with interacting on social media since a young age. Since technology can be instrumental in customizing learning experiences to meet the needs of all learners, can we successfully integrate it into our introductory chemistry courses to create a more inclusive, engaged and informed citizenry? This talk will describe specific ed-tech strategies, including online collaborative tools, discussion platforms, social media, and student created media implemented in the introductory chemistry courses taught at two very different undergraduate settings: one at a small liberal arts college (Wellesley College, MA), and one at a big research institution (Boston University, MA). The unifying goal of these practices was to help students practice transferring their learning to new contexts through individual reflection followed by group communication using a blended course design. What worked well and what did not in each setting, will be discussed.Accepted manuscrip