803 research outputs found
Creating User-Friendly Tools for Data Analysis and Visualization in K-12 Classrooms: A Fortran Dinosaur Meets Generation Y
During the summer of 2007, as part of the second year of a NASA-funded project in partnership with Christopher Newport University called SPHERE (Students as Professionals Helping Educators Research the Earth), a group of undergraduate students spent 8 weeks in a research internship at or near NASA Langley Research Center. Three students from this group formed the Clouds group along with a NASA mentor (Chambers), and the brief addition of a local high school student fulfilling a mentorship requirement. The Clouds group was given the task of exploring and analyzing ground-based cloud observations obtained by K-12 students as part of the Students' Cloud Observations On-Line (S'COOL) Project, and the corresponding satellite data. This project began in 1997. The primary analysis tools developed for it were in FORTRAN, a computer language none of the students were familiar with. While they persevered through computer challenges and picky syntax, it eventually became obvious that this was not the most fruitful approach for a project aimed at motivating K-12 students to do their own data analysis. Thus, about halfway through the summer the group shifted its focus to more modern data analysis and visualization tools, namely spreadsheets and Google(tm) Earth. The result of their efforts, so far, is two different Excel spreadsheets and a Google(tm) Earth file. The spreadsheets are set up to allow participating classrooms to paste in a particular dataset of interest, using the standard S'COOL format, and easily perform a variety of analyses and comparisons of the ground cloud observation reports and their correspondence with the satellite data. This includes summarizing cloud occurrence and cloud cover statistics, and comparing cloud cover measurements from the two points of view. A visual classification tool is also provided to compare the cloud levels reported from the two viewpoints. This provides a statistical counterpart to the existing S'COOL data visualization tool, which is used for individual ground-to-satellite correspondences. The Google(tm) Earth file contains a set of placemarks and ground overlays to show participating students the area around their school that the satellite is measuring. This approach will be automated and made interactive by the S'COOL database expert and will also be used to help refine the latitude/longitude location of the participating schools. Once complete, these new data analysis tools will be posted on the S'COOL website for use by the project participants in schools around the US and the world
Correlative Aberration-Corrected STEM-HAADF and STEM-EELS Analysis of Interface-Induced Polarization in LaCrO 3 -SrTiO 3 Superlattices
First-principles study of nucleation, growth, and interface structure of Fe/GaAs
We use density-functional theory to describe the initial stages of Fe film
growth on GaAs(001), focusing on the interplay between chemistry and magnetism
at the interface. Four features appear to be generic: (1) At submonolayer
coverages, a strong chemical interaction between Fe and substrate atoms leads
to substitutional adsorption and intermixing. (2) For films of several
monolayers and more, atomically abrupt interfaces are energetically favored.
(3) For Fe films over a range of thicknesses, both Ga- and As-adlayers
dramatically reduce the formation energies of the films, suggesting a
surfactant-like action. (4) During the first few monolayers of growth, Ga or As
atoms are likely to be liberated from the interface and diffuse to the Fe film
surface. Magnetism plays an important auxiliary role for these processes, even
in the dilute limit of atomic adsorption. Most of the films exhibit
ferromagnetic order even at half-monolayer coverage, while certain
adlayer-capped films show a slight preference for antiferromagnetic order.Comment: 11 two-column pages, 12 figures, to appear in Phys. Rev.
Interconversion of intrinsic defects in
Photoemission features associated with states deep in the band gap of n−SrTiO₃ (001) are found to be ubiquitous in bulk crystals and epitaxial films. These features are present even when there is little signal near the Fermi level. Analysis reveals that these states are deep-level traps associated with defects. The commonly investigated defects—O vacancies, Sr vacancies, and aliovalent impurity cations on the Ti sites—cannot account for these features. Rather, ab initio modeling points to these states resulting from interstitial oxygen and its interaction with donor electrons
High Energy Colliders as Black Hole Factories: The End of Short Distance Physics
If the fundamental Planck scale is of order a TeV, as the case in some
extra-dimensions scenarios, future hadron colliders such as the Large Hadron
Collider will be black hole factories. The non-perturbative process of black
hole formation and decay by Hawking evaporation gives rise to spectacular
events with up to many dozens of relatively hard jets and leptons, with a
characteristic ratio of hadronic to leptonic activity of roughly 5:1. The total
transverse energy of such events is typically a sizeable fraction of the beam
energy. Perturbative hard scattering processes at energies well above the
Planck scale are cloaked behind a horizon, thus limiting the ability to probe
short distances. The high energy black hole cross section grows with energy at
a rate determined by the dimensionality and geometry of the extra dimensions.
This dependence therefore probes the extra dimensions at distances larger than
the Planck scale.Comment: Latex, 28 pages. v4: minor changes, largely to agree with published
version; appendix added comparing convention
Characterization of Defects in Ion Transport and Tissue Development in Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)-Knockout Rats
Animal models for cystic fibrosis (CF) have contributed significantly to our understanding of disease pathogenesis. Here we describe development and characterization of the first cystic fibrosis rat, in which the cystic fibrosis transmembrane conductance regulator gene (CFTR) was knocked out using a pair of zinc finger endonucleases (ZFN). The disrupted Cftr gene carries a 16 base pair deletion in exon 3, resulting in loss of CFTR protein expression. Breeding of heterozygous (CFTR+/−) rats resulted in Mendelian distribution of wild-type, heterozygous, and homozygous (CFTR−/−) pups. Nasal potential difference and transepithelial short circuit current measurements established a robust CF bioelectric phenotype, similar in many respects to that seen in CF patients. Young CFTR−/− rats exhibited histological abnormalities in the ileum and increased intracellular mucus in the proximal nasal septa. By six weeks of age, CFTR−/− males lacked the vas deferens bilaterally. Airway surface liquid and periciliary liquid depth were reduced, and submucosal gland size was abnormal in CFTR−/− animals. Use of ZFN based gene disruption successfully generated a CF animal model that recapitulates many aspects of human disease, and may be useful for modeling other CF genotypes, including CFTR processing defects, premature truncation alleles, and channel gating abnormalities
Canvass: a crowd-sourced, natural-product screening library for exploring biological space
NCATS thanks Dingyin Tao for assistance with compound characterization. This research was supported by the Intramural Research Program of the National Center for Advancing Translational Sciences, National Institutes of Health (NIH). R.B.A. acknowledges support from NSF (CHE-1665145) and NIH (GM126221). M.K.B. acknowledges support from NIH (5R01GM110131). N.Z.B. thanks support from NIGMS, NIH (R01GM114061). J.K.C. acknowledges support from NSF (CHE-1665331). J.C. acknowledges support from the Fogarty International Center, NIH (TW009872). P.A.C. acknowledges support from the National Cancer Institute (NCI), NIH (R01 CA158275), and the NIH/National Institute of Aging (P01 AG012411). N.K.G. acknowledges support from NSF (CHE-1464898). B.C.G. thanks the support of NSF (RUI: 213569), the Camille and Henry Dreyfus Foundation, and the Arnold and Mabel Beckman Foundation. C.C.H. thanks the start-up funds from the Scripps Institution of Oceanography for support. J.N.J. acknowledges support from NIH (GM 063557, GM 084333). A.D.K. thanks the support from NCI, NIH (P01CA125066). D.G.I.K. acknowledges support from the National Center for Complementary and Integrative Health (1 R01 AT008088) and the Fogarty International Center, NIH (U01 TW00313), and gratefully acknowledges courtesies extended by the Government of Madagascar (Ministere des Eaux et Forets). O.K. thanks NIH (R01GM071779) for financial support. T.J.M. acknowledges support from NIH (GM116952). S.M. acknowledges support from NIH (DA045884-01, DA046487-01, AA026949-01), the Office of the Assistant Secretary of Defense for Health Affairs through the Peer Reviewed Medical Research Program (W81XWH-17-1-0256), and NCI, NIH, through a Cancer Center Support Grant (P30 CA008748). K.N.M. thanks the California Department of Food and Agriculture Pierce's Disease and Glassy Winged Sharpshooter Board for support. B.T.M. thanks Michael Mullowney for his contribution in the isolation, elucidation, and submission of the compounds in this work. P.N. acknowledges support from NIH (R01 GM111476). L.E.O. acknowledges support from NIH (R01-HL25854, R01-GM30859, R0-1-NS-12389). L.E.B., J.K.S., and J.A.P. thank the NIH (R35 GM-118173, R24 GM-111625) for research support. F.R. thanks the American Lebanese Syrian Associated Charities (ALSAC) for financial support. I.S. thanks the University of Oklahoma Startup funds for support. J.T.S. acknowledges support from ACS PRF (53767-ND1) and NSF (CHE-1414298), and thanks Drs. Kellan N. Lamb and Michael J. Di Maso for their synthetic contribution. B.S. acknowledges support from NIH (CA78747, CA106150, GM114353, GM115575). W.S. acknowledges support from NIGMS, NIH (R15GM116032, P30 GM103450), and thanks the University of Arkansas for startup funds and the Arkansas Biosciences Institute (ABI) for seed money. C.R.J.S. acknowledges support from NIH (R01GM121656). D.S.T. thanks the support of NIH (T32 CA062948-Gudas) and PhRMA Foundation to A.L.V., NIH (P41 GM076267) to D.S.T., and CCSG NIH (P30 CA008748) to C.B. Thompson. R.E.T. acknowledges support from NIGMS, NIH (GM129465). R.J.T. thanks the American Cancer Society (RSG-12-253-01-CDD) and NSF (CHE1361173) for support. D.A.V. thanks the Camille and Henry Dreyfus Foundation, the National Science Foundation (CHE-0353662, CHE-1005253, and CHE-1725142), the Beckman Foundation, the Sherman Fairchild Foundation, the John Stauffer Charitable Trust, and the Christian Scholars Foundation for support. J.W. acknowledges support from the American Cancer Society through the Research Scholar Grant (RSG-13-011-01-CDD). W.M.W.acknowledges support from NIGMS, NIH (GM119426), and NSF (CHE1755698). A.Z. acknowledges support from NSF (CHE-1463819). (Intramural Research Program of the National Center for Advancing Translational Sciences, National Institutes of Health (NIH); CHE-1665145 - NSF; CHE-1665331 - NSF; CHE-1464898 - NSF; RUI: 213569 - NSF; CHE-1414298 - NSF; CHE1361173 - NSF; CHE1755698 - NSF; CHE-1463819 - NSF; GM126221 - NIH; 5R01GM110131 - NIH; GM 063557 - NIH; GM 084333 - NIH; R01GM071779 - NIH; GM116952 - NIH; DA045884-01 - NIH; DA046487-01 - NIH; AA026949-01 - NIH; R01 GM111476 - NIH; R01-HL25854 - NIH; R01-GM30859 - NIH; R0-1-NS-12389 - NIH; R35 GM-118173 - NIH; R24 GM-111625 - NIH; CA78747 - NIH; CA106150 - NIH; GM114353 - NIH; GM115575 - NIH; R01GM121656 - NIH; T32 CA062948-Gudas - NIH; P41 GM076267 - NIH; R01GM114061 - NIGMS, NIH; R15GM116032 - NIGMS, NIH; P30 GM103450 - NIGMS, NIH; GM129465 - NIGMS, NIH; GM119426 - NIGMS, NIH; TW009872 - Fogarty International Center, NIH; U01 TW00313 - Fogarty International Center, NIH; R01 CA158275 - National Cancer Institute (NCI), NIH; P01 AG012411 - NIH/National Institute of Aging; Camille and Henry Dreyfus Foundation; Arnold and Mabel Beckman Foundation; Scripps Institution of Oceanography; P01CA125066 - NCI, NIH; 1 R01 AT008088 - National Center for Complementary and Integrative Health; W81XWH-17-1-0256 - Office of the Assistant Secretary of Defense for Health Affairs through the Peer Reviewed Medical Research Program; P30 CA008748 - NCI, NIH, through a Cancer Center Support Grant; California Department of Food and Agriculture Pierce's Disease and Glassy Winged Sharpshooter Board; American Lebanese Syrian Associated Charities (ALSAC); University of Oklahoma Startup funds; 53767-ND1 - ACS PRF; PhRMA Foundation; P30 CA008748 - CCSG NIH; RSG-12-253-01-CDD - American Cancer Society; RSG-13-011-01-CDD - American Cancer Society; CHE-0353662 - National Science Foundation; CHE-1005253 - National Science Foundation; CHE-1725142 - National Science Foundation; Beckman Foundation; Sherman Fairchild Foundation; John Stauffer Charitable Trust; Christian Scholars Foundation)Published versionSupporting documentatio
The APOGEE-2 Survey of the Orion Star Forming Complex: I. Target Selection and Validation with early observations
The Orion Star Forming Complex (OSFC) is a central target for the APOGEE-2
Young Cluster Survey. Existing membership catalogs span limited portions of the
OSFC, reflecting the difficulty of selecting targets homogeneously across this
extended, highly structured region. We have used data from wide field
photometric surveys to produce a less biased parent sample of young stellar
objects (YSOs) with infrared (IR) excesses indicative of warm circumstellar
material or photometric variability at optical wavelengths across the full 420
square degrees extent of the OSFC. When restricted to YSO candidates with H <
12.4, to ensure S/N ~100 for a six visit source, this uniformly selected sample
includes 1307 IR excess sources selected using criteria vetted by Koenig &
Liesawitz and 990 optical variables identified in the Pan-STARRS1 3
survey: 319 sources exhibit both optical variability and evidence of
circumstellar disks through IR excess. Objects from this uniformly selected
sample received the highest priority for targeting, but required fewer than
half of the fibers on each APOGEE-2 plate. We fill the remaining fibers with
previously confirmed and new color-magnitude selected candidate OSFC members.
Radial velocity measurements from APOGEE-1 and new APOGEE-2 observations taken
in the survey's first year indicate that ~90% of the uniformly selected targets
have radial velocities consistent with Orion membership.The APOGEE-2 Orion
survey will include >1100 bona fide YSOs whose uniform selection function will
provide a robust sample for comparative analyses of the stellar populations and
properties across all sub-regions of Orion.Comment: Accepted for publication in ApJ
Studies of the Suitability of Fowlpox as a Decontamination and Thermal Stability Simulant for Variola Major
Variola major, the causative agent of smallpox, has been eradicated from nature. However, stocks still exist; thus, there is a need for relevant decontamination studies, preferably with nonpathogenic simulants. Previous studies have shown a similarity in response of vaccinia virus and variola major to various decontaminants and thermal inactivation. This study compared vaccinia and fowlpox viruses under similar conditions, using disinfectants and temperatures for which variola major data already existed. Most disinfectants showed similar efficacy against vaccinia and fowlpox, suggesting the utility of fowlpox as a decontamination simulant. Inactivation kinetics studies showed that fowlpox behaved similarly to variola major when treated with 0.1% iodine and 5.7% polyethyleneglycol nonylphenyl ether, 0.025% sodium hypochlorite, 0.05% sodium hypochlorite, and 0.1% cetyltrimethylammonium chloride and 0.05% benzalkonium chloride, but differed in its response to 0.05% iodine and 0.3% polyethyleneglycol nonylphenyl ether and 40% ethanol. Thermal inactivation studies demonstrated that fowlpox is a suitable thermal simulant for variola major between 40°C and 55°C
Teratology Primer-2nd Edition (7/9/2010)
Foreword:
What is Teratology?
“What a piece of work is an embryo!” as Hamlet might have said. “In form and moving how express and admirable! In complexity how infinite!” It starts as a single cell, which by repeated divisions gives rise to many genetically identical cells. These cells receive signals from their surroundings and from one another as to where they are in this ball of cells —front or back, right or left, headwards or tailwards, and what they are destined to become. Each cell commits itself to being one of many types; the cells migrate, combine into tissues, or get out of the way by dying at predetermined times and places. The tissues signal one another to take their own pathways; they bend, twist, and form organs. An organism emerges. This wondrous transformation from single celled simplicity to myriad-celled complexity is programmed by genes that, in the greatest mystery of all, are turned on and off at specified times and places to coordinate the process. It is a wonder that this marvelously emergent operation, where there are so many opportunities for mistakes, ever produces a well-formed and functional organism.
And sometimes it doesn’t. Mistakes occur. Defective genes may disturb development in ways that lead to death or to malformations. Extrinsic factors may do the same. “Teratogenic” refers to factors that cause malformations, whether they be genes or environmental agents. The word comes from the Greek “teras,” for “monster,” a term applied in ancient times to babies with severe malformations, which were considered portents or, in the Latin, “monstra.”
Malformations can happen in many ways. For example, when the neural plate rolls up to form the neural tube, it may not close completely, resulting in a neural tube defect—anencephaly if the opening is in the head region, or spina bifida if it is lower down. The embryonic processes that form the face may fail to fuse, resulting in a cleft lip. Later, the shelves that will form the palate may fail to move from the vertical to the horizontal, where they should meet in the midline and fuse, resulting in a cleft palate. Or they may meet, but fail to fuse, with the same result. The forebrain may fail to induce the overlying tissue to form the eye, so there is no eye (anophthalmia). The tissues between the toes may fail to break down as they should, and the toes remain webbed.
Experimental teratology flourished in the 19th century, and embryologists knew well that the development of bird and frog embryos could be deranged by environmental “insults,” such as lack of oxygen (hypoxia). But the mammalian uterus was thought to be an impregnable barrier that would protect the embryo from such threats. By exclusion, mammalian malformations must be genetic, it was thought.
In the early 1940s, several events changed this view. In Australia an astute ophthalmologist, Norman Gregg, established a connection between maternal rubella (German measles) and the triad of cataracts, heart malformations, and deafness. In Cincinnati Josef Warkany, an Austrian pediatrician showed that depriving female rats of vitamin B (riboflavin) could cause malformations in their offspring— one of the early experimental demonstrations of a teratogen. Warkany was trying to produce congenital cretinism by putting the rats on an iodine deficient diet. The diet did indeed cause malformations, but not because of the iodine deficiency; depleting the diet of iodine had also depleted it of riboflavin!
Several other teratogens were found in experimental animals, including nitrogen mustard (an anti cancer drug), trypan blue (a dye), and hypoxia (lack of oxygen). The pendulum was swinging back; it seemed that malformations were not genetically, but environmentally caused.
In Montreal, in the early 1950s, Clarke Fraser’s group wanted to bring genetics back into the picture. They had found that treating pregnant mice with cortisone caused cleft palate in the offspring, and showed that the frequency was high in some strains and low in others. The only difference was in the genes. So began “teratogenetics,” the study of how genes influence the embryo’s susceptibility to teratogens.
The McGill group went on to develop the idea that an embryo’s genetically determined, normal, pattern of development could influence its susceptibility to a teratogen— the multifactorial threshold concept. For instance, an embryo must move its palate shelves from vertical to horizontal before a certain critical point or they will not meet and fuse. A teratogen that causes cleft palate by delaying shelf movement beyond this point is more likely to do so in an embryo whose genes normally move its shelves late.
As studies of the basis for abnormal development progressed, patterns began to appear, and the principles of teratology were developed. These stated, in summary, that the probability of a malformation being produced by a teratogen depends on the dose of the agent, the stage at which the embryo is exposed, and the genotype of the embryo and mother.
The number of mammalian teratogens grew, and those who worked with them began to meet from time to time, to talk about what they were finding, leading, in 1960, to the formation of the Teratology Society. There were, of course, concerns about whether these experimental teratogens would be a threat to human embryos, but it was thought, by me at least, that they were all “sledgehammer blows,” that would be teratogenic in people only at doses far above those to which human embryos would be exposed. So not to worry, or so we thought.
Then came thalidomide, a totally unexpected catastrophe. The discovery that ordinary doses of this supposedly “harmless” sleeping pill and anti-nauseant could cause severe malformations in human babies galvanized this new field of teratology. Scientists who had been quietly working in their laboratories suddenly found themselves spending much of their time in conferences and workshops, sitting on advisory committees, acting as consultants for pharmaceutical companies, regulatory agencies, and lawyers, as well as redesigning their research plans.
The field of teratology and developmental toxicology expanded rapidly. The following pages will show how far we have come, and how many important questions still remain to be answered. A lot of effort has gone into developing ways to predict how much of a hazard a particular experimental teratogen would be to the human embryo (chapters 9–19). It was recognized that animal studies might not prove a drug was “safe” for the human embryo (in spite of great pressure from legislators and the public to do so), since species can vary in their responses to teratogenic exposures. A number of human teratogens have been identified, and some, suspected of teratogenicity, have been exonerated—at least of a detectable risk (chapters 21–32). Regulations for testing drugs before market release have greatly improved (chapter 14). Other chapters deal with how much such things as population studies (chapter 11), post-marketing surveillance (chapter 13), and systems biology (chapter 16) add to our understanding. And, in a major advance, the maternal role of folate in preventing neural tube defects and other birth defects is being exploited (chapter 32). Encouraging women to take folic acid supplements and adding folate to flour have produced dramatic falls in the frequency of neural tube defects in many parts of the world.
Progress has been made not only in the use of animal studies to predict human risks, but also to illumine how, and under what circumstances, teratogens act to produce malformations (chapters 2–8). These studies have contributed greatly to our knowledge of abnormal and also normal development. Now we are beginning to see exactly when and where the genes turn on and off in the embryo, to appreciate how they guide development and to gain exciting new insights into how genes and teratogens interact. The prospects for progress in the war on birth defects were never brighter.
F. Clarke Fraser McGill University (Emeritus) Montreal, Quebec, Canad
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