Singing the Brain Electric

Thesis (S.M. in Science Writing)--Massachusetts Institute of Technology, Dept. of Humanities, Graduate Program in Science Writing, 2008.Includes bibliographical references (p. [36]-[38]).Singing the Brain Electric Brain pacemakers, scientists have found, can treat depression by correcting neural circuitry gone haywire. This thesis examines how such technology - a technique known as deep-brain stimulation, in which electrodes are implanted within the brain - was developed and how it works. We are introduced to a patient who received deep-brain stimulation for her refractory depression, and consider the risks, ethical issues, and questions of humanity and identity the technology raises.by Grace Chua.S.M.in Science Writin

A priori prediction of aggregation efficiency and rate constant for fluidized bed melt granulation

This paper presents a predictive aggregation rate model for spray fluidized bed melt granulation. The aggregation rate constant was derived from probability analysis of particle–droplet contact combined with time scale analysis of droplet solidification and granule–granule collision rates. The latter was obtained using the principles of kinetic theory of granular flow (KTGF). The predicted aggregation rate constants were validated by comparison with reported experimental data for a range of binder spray rate, binder droplet size and operating granulator temperature. The developed model is particularly useful for predicting particle size distributions and growth using population balance equations (PBEs)

InGaN nano-ring structures for high-efficiency light emitting diodes

A technique based on the Fresnel diffraction effect for the fabrication of nano-scale site-controlled ring structures in InGaN/GaN multi-quantum well structures has been demonstrated. The ring structures have an internal diameter of 500 nm and a wall width of 300 nm. A 1 cm-1 Raman shift has been measured, signifying substantial strain relaxation from the fabricated structure. The 9 nm blueshift observed in the cathodoluminescence spectra can be attributed to band filling and/or screening of the piezoelectric field. A light emitting diode based on this geometry has been demonstrated

Time scale analysis for fluidizedbedmeltgranulation III: binder solidification rate

In series I and II of this study ([Chua et al., 2010a] and [Chua et al., 2010b]), we discussed the time scale of granule–granule collision, droplet–granule collision and droplet spreading in Fluidized Bed Melt Granulation (FBMG). In this third one, we consider the rate at which binder solidifies. Simple analytical solution, based on classical formulation for conduction across a semi-infinite slab, was used to obtain a generalized equation for binder solidification time. A multi-physics simulation package (Comsol) was used to predict the binder solidification time for various operating conditions usually considered in FBMG. The simulation results were validated with experimental temperature data obtained with a high speed infrared camera during solidification of ‘macroscopic’ (mm scale) droplets. For the range of microscopic droplet size and operating conditions considered for a FBMG process, the binder solidification time was found to fall approximately between 10-3 and 10-1 s. This is the slowest compared to the other three major FBMG microscopic events discussed in this series (granule–granule collision, granule–droplet collision and droplet spreading)

Structural Characterization of Rapid Thermal Oxidized Si\u3csub\u3e1−x−y\u3c/sub\u3eGe\u3csub\u3ex\u3c/sub\u3eC\u3csub\u3ey\u3c/sub\u3e Alloy Films Grown by Rapid Thermal Chemical Vapor Deposition

The structural properties of as-grown and rapid thermal oxidized Si1−x−yGexCy epitaxial layers have been examined using a combination of infrared, x-ray photoelectron, x-ray diffraction, secondary ion mass spectroscopy, and Raman spectroscopy techniques. Carbon incorporation into the Si1−x−yGexCy system can lead to compressive or tensile strain in the film. The structural properties of the oxidized Si1−x−yGexCy film depend on the type of strain (i.e., carbon concentration) of the as-prepared film. For compressive or fully compensated films, the oxidation process drastically reduces the carbon content so that the oxidized films closely resemble to Si1−xGex films. For tensile films, two broad regions, one with carbon content higher and the other lower than that required for full strain compensation, coexist in the oxidized films

Interacting classical and quantum particles

We apply Hall and Reginatto's theory of interacting classical and quantum ensembles to harmonically coupled particles, with a view to understanding its experimental implications. This hybrid theory has no free parameters and makes distinctive predictions that should allow it to be experimentally distinguished from quantum mechanics. It also bears on the questions of quantum measurement and quantum gravity.Comment: 7 pages, 6 figure

Human Life History Strategies: Calibrated to External or Internal Cues?

Human life history (LH) strategies are theoretically regulated by developmental exposure to environmental cues that ancestrally predicted LH-relevant world states (e.g., risk of morbidity-mortality). Recent modeling work has raised the question of whether the association of childhood family factors with adult LH variation arises via (i) direct sampling of external environmental cues during development and/or (ii) calibration of LH strategies to internal somatic condition (i.e., health), which itself reflects exposure to variably favorable environments. The present research tested between these possibilities through three online surveys involving a total of over 26,000 participants. Participants completed questionnaires assessing components of self-reported environmental harshness (i.e., socioeconomic status, family neglect, and neighborhood crime), health status, and various LH-related psychological and behavioral phenotypes (e.g., mating strategies, paranoia, and anxiety), modeled as a unidimensional latent variable. Structural equation models suggested that exposure to harsh ecologies had direct effects on latent LH strategy as well as indirect effects on latent LH strategy mediated via health status. These findings suggest that human LH strategies may be calibrated to both external and internal cues and that such calibrational effects manifest in a wide range of psychological and behavioral phenotypes

The Neutrino Magnetic Moment Induced by Leptoquarks

Allowing leptoquarks to interact with both right-handed and left-handed neutrinos (i.e., ``non-chiral'' leptoquarks), we show that a non-zero neutrino magnetic moment can arise naturally. Although the mass of the non-chiral vector leptoquark that couples to the first generation fermions is constrained severely by universality of the $\pi^+$ leptonic decays and is found to be greater than 50 TeV, the masses of the second and third generation non-chiral vector leptoquarks may evade such constraint and may in general be in the range of $1\sim 100$ TeV. With reasonable input mass and coupling values, we find that the neutrino magnetic moment due to the second generation leptoquarks is of the order of $10^{-12}\sim 10^{-16} \mu_{\rm B}$ while that caused by the third generation leptoquarks, being enhanced significantly by the large top quark mass, is in the range of $10^{-10}\sim 10^{-14} \mu_{\rm B}$.Comment: 11 pages, 3 eps figures, uses revte

The Fourth Element: Characteristics, Modelling, and Electromagnetic Theory of the Memristor

In 2008, researchers at HP Labs published a paper in {\it Nature} reporting the realisation of a new basic circuit element that completes the missing link between charge and flux-linkage, which was postulated by Leon Chua in 1971. The HP memristor is based on a nanometer scale TiO$_2$ thin-film, containing a doped region and an undoped region. Further to proposed applications of memristors in artificial biological systems and nonvolatile RAM (NVRAM), they also enable reconfigurable nanoelectronics. Moreover, memristors provide new paradigms in application specific integrated circuits (ASICs) and field programmable gate arrays (FPGAs). A significant reduction in area with an unprecedented memory capacity and device density are the potential advantages of memristors for Integrated Circuits (ICs). This work reviews the memristor and provides mathematical and SPICE models for memristors. Insight into the memristor device is given via recalling the quasi-static expansion of Maxwell's equations. We also review Chua's arguments based on electromagnetic theory.Comment: 28 pages, 14 figures, Accepted as a regular paper - the Proceedings of Royal Society

Myeloperoxidase As a Multifaceted Target for Cardiovascular Protection

SIGNIFICANCE: Myeloperoxidase (MPO) is a heme peroxidase that is primarily expressed by neutrophils. It has the capacity to generate several reactive species, essential for its inherent antimicrobial activity and innate host defense. Dysregulated MPO release however, can lead to tissue damage, as seen in several diseases. Increased MPO levels in circulation is therefore, widely associated with conditions of increased oxidative stress and inflammation. Recent Advances: Several studies have shown a strong correlation between MPO and cardiovascular disease (CVD), whereby elevated levels of circulating MPO are linked to poor prognosis with increased risk of CVD-related mortality. Accordingly, circulating MPO is considered a 'high-risk' biomarker for patients with acute coronary syndrome, atherosclerosis, heart failure, hypertension and stroke, thereby implicating MPO as a multifaceted target for cardiovascular protection. Consistently, recent studies that target MPO in animal models of CVD have demonstrated favorable outcomes with regard to disease progression. CRITICAL ISSUES: Although most of these studies have established a critical link between circulating MPO and worsening cardiac outcomes, the mechanisms by which MPO exerts its detrimental effects in CVD remain unclear. FUTURE DIRECTIONS: Elucidating the mechanisms by which elevated MPO leads to poor prognosis and conversely, investigating the beneficial effects of therapeutic MPO inhibition on alleviating disease phenotype, will facilitate future MPO-targeted clinical trials for improving CVD-related outcomes