4,033 research outputs found
Possible Applications of Dissolution Dynamic Nuclear Polarization in Conjunction with Zero- to Ultralow-Field Nuclear Magnetic Resonance
The combination of a powerful and broadly applicable nuclear
hyperpolarization technique with emerging (near-)zero-field modalities offer
novel opportunities in a broad range of nuclear magnetic resonance spectroscopy
and imaging applications, including biomedical diagnostics, monitoring
catalytic reactions within metal reactors and many others. These are discussed
along with a roadmap for future developments.Comment: 12 pages, 5 figure
Exploring the NRO Opportunity for a Hubble-sized Wide-field Near-IR Space Telescope -- NEW WFIRST
We discuss scientific, technical and programmatic issues related to the use
of an NRO 2.4m telescope for the WFIRST initiative of the 2010 Decadal Survey.
We show that this implementation of WFIRST, which we call "NEW WFIRST," would
achieve the goals of the NWNH Decadal Survey for the WFIRST core programs of
Dark Energy and Microlensing Planet Finding, with the crucial benefit of deeper
and/or wider near-IR surveys for GO science and a potentially Hubble-like Guest
Observer program. NEW WFIRST could also include a coronagraphic imager for
direct detection of dust disks and planets around neighboring stars, a
high-priority science and technology precursor for future ambitious programs to
image Earth-like planets around neighboring stars.Comment: 76 pages, 26 figures -- associated with the Princeton "New Telescope
Meeting
Direct observation of hyperpolarization breaking through the spin diffusion barrier
Dynamic nuclear polarization (DNP) is a widely used tool for overcoming the low intrinsic sensitivity of nuclear magnetic resonance spectroscopy and imaging. Its practical applicability is typically bounded, however, by the so-called 'spin diffusion barrier', which relates to the poor efficiency of polarization transfer from highly polarized nuclei close to paramagnetic centers to bulk nuclei. A quantitative assessment of this barrier has been hindered so far by the lack of general methods for studying nuclear-polarization flow in the vicinity of paramagnetic centers. Here we fill this gap and introduce a general set of experiments based on microwave gating that are readily implemented. We demonstrate the versatility of our approach in experiments conducted between 1.2 â 4.2 K in static mode and at 100 K under magic angle spinning (MAS) â conditions typical for dissolution-DNP and MAS-DNP â and for the first time directly observe the dramatic dependence of polarization flow on temperature.The data are organized in subfolders. A PDF document in the root folder summarizes the list of all experiments in the dataset with precisions on experimental parameters and remarks (README.pdf). For each subfolder, the figures of the paper which were produced using the data is the subfolder is listed.
Funding provided by: European Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000781Award Number: 714519: HP4allFunding provided by: H2020 Marie SkĆodowska-Curie ActionsCrossref Funder Registry ID: http://dx.doi.org/10.13039/100010665Award Number: 766402: ZULFFunding provided by: NSF/DMR and the State of Florida*Crossref Funder Registry ID: Award Number: 1644779Funding provided by: NSF/DMR NIH*Crossref Funder Registry ID: Award Number: S10 OD018519Funding provided by: National Institutes of HealthCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000002Award Number: P41 GM122698 01Funding provided by: National Science FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000001Award Number: CHE 1229170Funding provided by: NSF/DMR and the State of FloridaCrossref Funder Registry ID: Award Number: 1644779Funding provided by: NSF/DMR NIHCrossref Funder Registry ID: Award Number: S10 OD018519All data consist of NMR spectra. Data were collected using high field NMR instruments by Bruker using the software Topspin 3.5.7 and Topspin 3.6.2. They were exported to CSV files
X-Ray- and Neutron-Scattering Studies of α-Crystallin and Evidence That the Target Protein Sits in the Fenestrations of the α-Crystallin Shell
PURPOSE. α-Crystallin, a ubiquitous molecular chaperone, is found in high concentrations in the lens. Its structure and precise mechanism of action, however, are unknown. The purpose of these experiments was to further the understanding of the chaperone function of α-crystallin.
METHODS. X-ray- and neutron-solution-scattering studies were used to measure the radius of gyration of bovine lens α-crystallin when complexed with its target protein ÎČ-crystallin in both normal and heavy-water-based solutions. Spectrophotometry was used as a chaperone assay.
RESULTS. The radius of gyration of α-crystallin on its own and when mixed with ÎČ-crystallin was 69 ± 1 Ă
at 35°C and increased with the temperature. In contrast to H2O-buffered solutions, the radius of gyration did not increase significantly in D2O-buffered solutions up to 55°C, and at 70°C was, on average, some 15 to 20 Ă
smaller.
CONCLUSIONS. Bovine lens α-crystallin in solution can be modeled as a fenestrated spherical shell of diameter 169 Ă
. At physiological temperatures, a weak interaction between α- and ÎČ-crystallin occurs, and ÎČ-crystallin is located in the fenestrations. Deuterium substitution indicates that the superaggregation process is controlled by hydrogen bonding. However, the chaperone process and superaggregation appear not to be linked
Pulse sequence and sample formulation optimization for dipolar order mediated 1H-13C cross-polarization
We have recently demonstrated the use of contactless radiofrequency pulse sequences under dissolution-dynamic nuclear polarization conditions as an attractive way of transferring polarization from sensitive 1H spins to insensitive 13C spins with low peak radiofrequency pulse powers and energies via a reservoir of dipolar order. However, many factors remain to be investigated and optimized to enable the full potential of this polarization transfer process. We demonstrate herein the optimization of several key factors by: (i) implementing more efficient shaped radiofrequency pulses; (ii) adapting 13C spin labelling; and (iii) avoiding methyl group relaxation sinks. Experimental demonstrations are presented for the case of [1-13C]sodium acetate and other relevant molecular candidates. By employing the range of approaches set out above, polarization transfer using the dipolar order mediated cross-polarization radiofrequency pulse sequence is improved by factors approaching âŒ1.65 compared with previous results. Dipolar order mediated 1Hâ13C polarization transfer efficiencies reaching âŒ76% were achieved using significantly reduced peak radiofrequency pulse powers relative to the performance of highly sophisticated state-of-the-art cross-polarization methods, indicating 13C nuclear spin polarization levels on the order of âŒ32.1% after 10 minutes of 1H DNP. The approach does not require extensive pulse sequence optimization procedures and can easily accommodate high concentrations of 13C-labelled molecules
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Identification and Characterization of Small Molecule Inhibitors of a Class I Histone Deacetylase from Plasmodium falciparum
A library of approximately 2000 small molecules biased toward inhibition of histone deacetylases was assayed for antimalarial activity in a high-throughput P. falciparum viability assay. Active compounds were cross-analyzed for induction of histone hyperacetylation in a human myeloma cell line to identify HDAC inhibitors with selectivity for P. falciparum over the human host. To verify on-target selectivity, pfHDAC-1 was expressed and purified and a biochemical assay for pfHDAC-1 activity was established.Chemistry and Chemical Biolog
Data Assimilation Enhancements to Air Force Weathers Land Information System
The United States Air Force (USAF) has a proud and storied tradition of enabling significant advancements in the area of characterizing and modeling land state information. 557th Weather Wing (557 WW; DoDs Executive Agent for Land Information) provides routine geospatial intelligence information to warfighters, planners, and decision makers at all echelons and services of the U.S. military, government and intelligence community. 557 WW and its predecessors have been home to the DoDs only operational regional and global land data analysis systems since January 1958. As a trusted partner since 2005, Air Force Weather (AFW) has relied on the Hydrological Sciences Laboratory at NASA/GSFC to lead the interagency scientific collaboration known as the Land Information System (LIS). LIS is an advanced software framework for high performance land surface modeling and data assimilation of geospatial intelligence (GEOINT) information
Social Salience and the Sociolinguistic Monitor: A Case Study of ING and TH-fronting in Britain
This article examines the role of social salience, or the relative ability of a linguistic variable to evoke social meaning, in structuring listenersâ perceptions of quantitative sociolinguistic distributions. Building on the foundational work of Labov et al. (2006, 2011) on the âsociolinguistic monitorâ (a proposed cognitive mechanism responsible for sociolinguistic perception), we examine whether listenersâ evaluative judgments of speech change as a function of the type of variable presented. We consider two variables in British English, ING and TH-fronting, which we argue differ in their relative social salience. Replicating the design of Labov et al.âs studies, we test 149 British listenersâ reactions to different quantitative distributions of these variables. Our experiments elicit a very different pattern of perceptual responses than those reported previously. In particular, our results suggest that a variableâs social salience determines both whether and how it is perceptually evaluated. We argue that this finding is crucial for understanding how sociolinguistic information is cognitively processed
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
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