On the sources of the height–intelligence correlation: New insights from a bivariate ACE model with assortative mating

A robust positive correlation between height and intelligence, as measured by IQ tests, has been established in the literature. This paper makes several contributions toward establishing the causes of this association. First, we extend the standard bivariate ACE model to account for assortative mating. The more general theoretical framework provides several key insights, including formulas to decompose a cross-trait genetic correlation into components attributable to assortative mating and pleiotropy and to decompose a cross-trait within-family correlation. Second, we use a large dataset of male twins drawn from Swedish conscription records and examine how well genetic and environmental factors explain the association between (i) height and intelligence and (ii) height and military aptitude, a professional psychogologist’s assessment of a conscript’s ability to deal with wartime stress. For both traits, we find suggestive evidence of a shared genetic architecture with height, but we demonstrate that point estimates are very sensitive to assumed degrees of assortative mating. Third, we report a significant within-family correlation between height and intelligence \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(\hat{\rho}=0.10),$$\end{document} suggesting that pleiotropy might be at play

Synthesis of inorganic semiconductor NC materials for the purpose of creating hybrid organic/inorganic LEDs

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.Includes bibliographical references.Colloidal semiconductor nanocrystals (NCs) or quantum dots (QDs) can be synthesized to efficiently emit light from the ultraviolet, across the entire visible spectrum, and into the near infrared. This is now possible due to the continual development of new core and core-shell NC structures to meet specific color needs in areas as diverse as optoelectronic devices to biological imaging. Core-shell semiconductor NCs are unique light emitters. They are more stable overtime to photobleaching compared to organic dyes. Their emission is efficient and their spectral full width at half maximum remains highly narrow as their size is synthetically changed to provide desired peak wavelengths of emission to within plus or minus a couple of nanometers. They can be purified and manipulated in solution and their chemical interaction with the environment is the same for all sizes and can be modified using chemical techniques. These unique properties make semiconductor NCs ideal for use in light emitting devices (QD-LEDs). This work shows how electroluminescence can be extended into the near infrared region of the spectrum by employing infrared emitting NCs as well as into the blue region of the spectrum by designing and synthesizing NCs specifically for this application.(cont.) Once efficient and color saturated electroluminescence at the visible spectrum's extremes had been realized it was a natural extension to begin exploring the potential of QD-LED devices to satisfy the technological requirements of flat panel displays and imaging applications. This led to the synthesis of a new green-emitting core-shell NC material to meet the specific color needs for flat panel display applications. At the same time we developed a new QD-LED device fabrication method to allow the patterning of the NC monolayer in our devices. Micro-contact printing the NC monolayer instead of using phase separation provided efficient and highly color saturated QD--LEDs in the red, green, and blue, and allowed us to pattern these monolayers towards the development of pixelated QD-LEDs such as needed for flat panel display applications. Along the way, the synthesis of colloidal NCs was studied to allow for more control in synthesizing higher quality materials in the future. The simple synthesis of PbSe NCs was used as a model system to begin to understand the mechanism of how the molecular precursors are reduced in solution to produce solid crystalline material in the presence of phosphorous containing molecules.by Jonathan S. Steckel.Ph.D

Red, green and blue lasing enabled by single-exciton gain in colloidal quantum dot films

Colloidal quantum dots exhibit efficient photoluminescence with widely tunable bandgaps as a result of quantum confinement effects1. Such quantum dots are emerging as an appealing complement to epitaxial semiconductor laser materials, which are ubiquitous and technologically mature, but unable to cover the full visible spectrum (red, green and blue; RGB)2. However, the requirement for high colloidal-quantum-dot packing density, and losses due to non-radiative multiexcitonic Auger recombination, have hindered the development of lasers based on colloidal quantum dots3, 4, 5, 6, 7, 8, 9. Here, we engineer CdSe/ZnCdS core/shell colloidal quantum dots with aromatic ligands, which form densely packed films exhibiting optical gain across the visible spectrum with less than one exciton per colloidal quantum dot on average. This single-exciton gain allows the films to reach the threshold of amplified spontaneous emission at very low optical pump energy densities of 90 µJ cm–2, more than one order of magnitude better than previously reported values9, 10, 11, 12. We leverage the low-threshold gain of these nanocomposite films to produce the first colloidal-quantum-dot vertical-cavity surface-emitting lasers (CQD-VCSEL). Our results represent a significant step towards full-colour single-material lasers.Accepted versio

Surface-emitting red, green, and blue colloidal quantum dot distributed feedback lasers

We demonstrate surface emitting distributed feedback (DFB) lasers across the red, green, and blue from densely packed colloidal quantum dot (CQD) films. The solid CQD films were deposited on periodic grating patterns to enable 2nd-order DFB lasing action at mere 120, 280, and 330 μJ/cm2 of optical pumping energy densities for red, green, and blue DFB lasers, respectively. The lasers operated in single mode operation with less than 1 nm of full-width-half-maximum. We measured far-field patterns showing high degree of spatial beam coherence. Specifically, by taking advantage of single exciton optical gain regime from our engineered CQDs, we can significantly suppress the Auger recombination to reduce lasing threshold and achieve quasi-steady state, optically pumped operation.Published versio