Solar driven lasers for power satellite applications

The technological feasibility of using multimagawatt lasers for space power transmission is discussed. Candidate lasers include electric discharge lasers, direct optically pumped lasers, and free electron lasers

Our Liberty Most Dear : The Political Reforms of John C. Calhoun

This article discusses the beliefs of John Calhoun, who was a strong supporter of states\u27 rights. He also believed that political minorities needed to be protected against the tyranny of the majority

Dissociation of multiply charged negative ions for hirudin (54–65), fibrinopeptide B, and insulin A (oxidized)

AbstractCollision-induced dissociation (CID) was performed on multiply deprotonated ions from three commercial peptides: hirudin (54–65), fibrinopeptide B, and oxidized insulin chain A. Ions were produced by electrospray ionization in a Fourier transform ion cyclotron resonance mass spectrometer. Each of these peptides contains multiple acidic residues, which makes them very difficult to ionize in the positive mode. However, the peptides deprotonate readily making negative ion studies a viable alternative. The CID spectra indicated that the likely deprotonation sites are acidic residues (aspartic, glutamic, and cysteic acids) and the C-terminus. The spectra are rife with c, y, and internal ions, although some a, b, x, and z ions form. Many of the fragment ions were formed from cleavage adjacent to acidic residues, both N- and C-terminal to the acidic site. In addition, neutral loss (e.g., NH3, CH3, H2O, and CO2) was prevalent from both the parent ions and from fragment ions. These neutral eliminations were often indicative of specific amino acid residues. The fragmentation patterns from several charge states of the parent ions, when combined, provide significant primary sequence information. These results suggest that negative mode CID of multiply deprotonated ions provides useful structural information and can be worthwhile for highly acidic peptides that do not form positive ions in abundance

Determination of kynurenine-3-hydroxylase

Determination of kynurenine-3-hydroxylas

RANDOM MODELS WITH DIRECT AND COMPETITION GENETIC EFFECTS

Livestock producers often select for animals which are genetically superior for yield. Competition among animals in the same pen may affect yield of pen mates. If competitiveness has a genetic component, selection should be for direct genetic effects for yield and for genetic effects of competitiveness on yield of penmates (Muir and Schinkel, 2002). This simulation study examined estimates of variance components from models which ignored competition effects. A population structure of 642 related animals was created. Random effects were residual and pen effects and direct and competition genetic values with genetic correlation. Conclusions, based on 400 replications for 16 different sets of variance parameters, were that competition effects, if ignored, may inflate estimates of pen variance and of direct genetic variance and that ignoring pen effects may increase estimates of the genetic correlation and both genetic variances. Key words: Associative Effects, Genetic Correlation, REM

Transdifferentiation of fibroblasts to neural stem cells

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references.The developmental process is carefully controlled by transcriptional and epigenetic changes that occur as a zygote transforms into an adult organism. This process can be reversed by the overexpression of transcription factors Oct4, Sox2, Klf4, and c-Myc, which reprogram a differentiated cell!s nucleus to one that is transcriptionally and epigenetically indistinguishable from an embryonic stem (ES) cell. However, it is still unclear if transcription factors can completely convert the nucleus of a differentiated cell into that of a distantly related somatic cell type with complete transcriptional and epigenetic reprogramming maintained in the absence of exogenous factor expression. To test this idea, we generated doxycyline (dox)-inducible vectors encoding neural stem cell-expressed factors. We found that stable, self-maintaining NSC-like cells could be induced under defined growth conditions. These cells were characterized in the absence of exogenous factor induction and were shown to be transcriptionally, epigenetically, and functionally similar to endogenous embryonic cortical NSCs. Additionally, a cellular system was created for reproducible generation of doxindependent iNSCs without additional factor transduction. Our results show that a transcriptionally and epigenetically reprogrammed somatic nucleus can be stabilized in vitro and provides a tool to study the mechanism of somatic cell conversion.by John P. Cassady.Ph.D

SEPARATION OF MITOCHONDRIAL MEMBRANES OF NEUROSPORA CRASSA : II. Submitochondrial Localization of the Isoleucine-Valine Biosynthetic Pathway

Separation of Neurospora mitochondrial outer membranes from the inner membrane/matrix fraction was effected by digitonin treatment and discontinuous density gradient centrifugation. The solubilization of four isoleucine-valine biosynthetic enzymes was studied as a function of digitonin concentration and time of incubation in the detergent. The kinetics of the appearance of valine biosynthetic function in fractions outside of the inner membrane/matrix fraction, coupled with enzyme solubilization patterns similar to that for the matrix marker, mitochondrial malate dehydrogenase, indicate that the four isoleucine-valine pathway enzymes are localized in the mitochondrial matrix