481 research outputs found
AN INVESTIGATION INTO THE ANALYTICAL UTILITY OF CHANGES IN POLARIZATION ACCOMPANYING ANALYTICAL DERIVATIZATION REACTIONS (FLUORESCENCE)
Derivatization reactions between amines, alcohols and carbonyl groups with various reagents were studied. The goal of the work discussed in this dissertation was to generate basic data to know whether and in what context changes in fluorescence polarization are useful for following analytical derivatization reactions.
Reactions between primary amines and fluorescein isothiocyanate were initially studied. Changes in polarization were observed upon conjugation for many of the amines primarily due to changes in fluorescence lifetime. This reaction was also studied in varying amounts of glycerol to judge the effect of glycerol on the reaction rate. Optimum percentages of glycerol were determined. Rate data of reactions of fluorescein isothiocyanate with aniline and p-chloroaniline are reported.
Reactions between amines and alcohols with dichlorotriazinyl fluorescein were studied next. Minimal changes in polarization were observed upon conjugation because the lifetimes were very similar to that of the reagent. Glycerol was a problem as it reacts rapidly with the reagent. In a set of kinetics experiments with polyethyleneimine, changes in polarization were observed but could not be distinguished from randomness brought about by the experimental conditions.
Dansyl chloride was more difficult to work with than either of the fluorescein compounds due to its sensitivity to environment. This was illustrated by dramatic changes in lifetime as the amount of glycerol in the solution was varied for Perrin plots.
The final study involved dansyl hydrazine and reactions with carbonyls. Polarizations again changed upon conjugation due to lifetime changes. Spectral shifts were also noted upon conjugation to two carbonyl compounds. Rate data for reactions with anisaldehyde are reported. A different TLC solvent system is suggested for separation of conjugate and free dansyl hydrazine
Effects of fungicide application timing and cultivar resistance on Fusarium head blight and deoxynivalenol in winter wheat
Fusarium graminearum causes Fusarium head blight (FHB) in wheat. FHB reduces yield and quality and contaminates grain with the mycotoxin deoxynivalenol (DON). Effective management strategies are needed. The objectives of this research were to 1) Determine the effect of fungicide application timing at anthesis (the standard timing) and 6 and 12 days later on FHB and DON in the winter wheat cultivars Overley (susceptible) and Overland (moderately resistant) and 2) Compare the effects of a triazole and a strobilurin fungicide on FHB and DON in Overley and Overland. In 2015 two field trials (irrigated and rain-fed) were conducted in Nebraska, USA. The triazole Prosaro (prothioconazole + tebuconazole) and the strobilurin Headline (pyraclostrobin) were applied with a CO2-powered backpack sprayer at anthesis and 6 and 12 days later. A split plot design in randomized complete blocks with 4 replications was used. Main plots were cultivars and subplots were fungicide treatments. FHB index and DON were significantly (P \u3c 0.05) lower in Overland than in Overley. The window of fungicide application to control FHB and DON was widened from anthesis to 6 days later without loss of efficacy. Headline was less effective than Prosaro in controlling FHB and DON. Moderate resistance combined with a triazole fungicide most effectively reduced FHB and DON. The results indicate a wider fungicide application window and the effectiveness of combining resistance with a triazole fungicide
Methods for Compression of Feedback in Adaptive Multicarrier 4G Schemes
In this paper, several algorithms for compressing the feedback of channel quality
information are presented and analyzed. These algorithms are developed for a proposed
adaptive modulation scheme for future multi-carrier 4G mobile systems. These strategies
compress the feedback data and, used together with opportunistic scheduling, drastically
reduce the feedback data rate. Thus the adaptive modulation schemes become more suitable
and efficient to be implemented in future mobile systems, increasing data throughput and
overall system performance.This work has been partly funded by the Spanish government with projects MACAWI
(TEC 2005-07477-c02-02), MAMBO2 (CCG06-UC3M-TIC-0698), and European COST Action 289 and is
a result of work done within this European actio
Commensurate and Incommensurate Vortex States in Superconductors with Periodic Pinning Arrays
As a function of applied field, we find a rich variety of ordered and
partially-ordered vortex lattice configurations in systems with square or
triangular arrays of pinning sites. We present formulas that predict the
matching fields at which commensurate vortex configurations occur and the
vortex lattice orientation with respect to the pinning lattice. Our results are
in excellent agreement with recent imaging experiments on square pinning arrays
[K. Harada et al., Science 274, 1167 (1996)].Comment: 9 pages, 3 figures. Accepted to Physical Review
FGDB: revisiting the genome annotation of the plant pathogen Fusarium graminearum
The MIPS Fusarium graminearum Genome Database (FGDB) was established as a comprehensive genome database on one of the most devastating fungal plant pathogens of wheat, barley and maize. The current version of FGDB v3.1 provides information on the full manually revised gene set based on the Broad Institute assembly FG3 genome sequence. The results of gene prediction tools were integrated with the help of comparative data on related species to result in a set of 13.718 annotated protein coding genes. This rigorous approach involved adding or modifying gene models and represents a coding sequence gold standard for the genus Fusarium. The gene loci improvements results in 2461 genes which either are new or have different structures compared to the Broad Institute assembly 3 gene set. Moreover the database serves as a convenient entry point to explore expression data results and to obtain information on the Affymetrix GeneChip probe sets. The resource is accessible on http://mips.gsf.de/genre/proj/FGDB/
Melting and transverse depinning of driven vortex lattices in the periodic pinning of Josephson junction arrays
We study the non-equilibrium dynamical regimes of a moving vortex lattice in
the periodic pinning of a Josephson junction array (JJA) for {\it finite
temperatures} in the case of a fractional or submatching field. We obtain a
phase diagram for the current driven JJA as a function of the driving current I
and temperature T. We find that when the vortex lattice is driven by a current,
the depinning transition at and the melting transition at
become separated even for a field for which they coincide in equilibrium. We
also distinguish between the depinning of the vortex lattice in the direction
of the current drive, and the {\it transverse depinning} in the direction
perpendicular to the drive. The transverse depinning corresponds to the onset
of transverse resistance in a moving vortex lattice at a given temperature
. For driving currents above the critical current we find that the
moving vortex lattice has first a transverse depinning transition at low T, and
later a melting transition at a higher temperature, .Comment: 17 pages, 19 figure
Spatio-temporal dynamics and plastic flow of vortices in superconductors with periodic arrays of pinning sites
We present simulations of flux-gradient-driven superconducting rigid vortices
interacting with square and triangular arrays of columnar pinning sites in an
increasing external magnetic field. These simulations allow us to
quantitatively relate spatio-temporal microscopic information of the vortex
lattice with typically measured macroscopic quantities, such as the
magnetization . The flux lattice does not become completely commensurate
with the pinning sites throughout the sample at the magnetization matching
peaks, but forms a commensurate lattice in a region close to the edge of the
sample. Matching fields related to unstable vortex configurations do not
produce peaks in . We observe a variety of evolving complex flux
profiles, including flat terraces or plateaus separated by winding
current-carrying strings and, near the peaks in , plateaus only in
certain regions, which move through the sample as the field increases
Search for non-relativistic Magnetic Monopoles with IceCube
The IceCube Neutrino Observatory is a large Cherenkov detector instrumenting
of Antarctic ice. The detector can be used to search for
signatures of particle physics beyond the Standard Model. Here, we describe the
search for non-relativistic, magnetic monopoles as remnants of the GUT (Grand
Unified Theory) era shortly after the Big Bang. These monopoles may catalyze
the decay of nucleons via the Rubakov-Callan effect with a cross section
suggested to be in the range of to
. In IceCube, the Cherenkov light from nucleon decays
along the monopole trajectory would produce a characteristic hit pattern. This
paper presents the results of an analysis of first data taken from May 2011
until May 2012 with a dedicated slow-particle trigger for DeepCore, a
subdetector of IceCube. A second analysis provides better sensitivity for the
brightest non-relativistic monopoles using data taken from May 2009 until May
2010. In both analyses no monopole signal was observed. For catalysis cross
sections of the flux of non-relativistic
GUT monopoles is constrained up to a level of at a 90% confidence level,
which is three orders of magnitude below the Parker bound. The limits assume a
dominant decay of the proton into a positron and a neutral pion. These results
improve the current best experimental limits by one to two orders of magnitude,
for a wide range of assumed speeds and catalysis cross sections.Comment: 20 pages, 20 figure
Search for Prompt Neutrino Emission from Gamma-Ray Bursts with IceCube
We present constraints derived from a search of four years of IceCube data
for a prompt neutrino flux from gamma-ray bursts (GRBs). A single
low-significance neutrino, compatible with the atmospheric neutrino background,
was found in coincidence with one of the 506 observed bursts. Although GRBs
have been proposed as candidate sources for ultra-high energy cosmic rays, our
limits on the neutrino flux disfavor much of the parameter space for the latest
models. We also find that no more than of the recently observed
astrophysical neutrino flux consists of prompt emission from GRBs that are
potentially observable by existing satellites.Comment: 15 pages, 3 figure
Searches for Extended and Point-like Neutrino Sources with Four Years of IceCube Data
We present results on searches for point-like sources of neutrinos using four
years of IceCube data, including the first year of data from the completed
86-string detector. The total livetime of the combined dataset is 1,373 days.
For an E spectrum the median sensitivity at 90\% C.L. is
TeVcms for energies between 1 TeV1 PeV in the northern
sky and TeVcms for energies between 100
TeV 100 PeV in the southern sky. The sensitivity has improved from both the
additional year of data and the introduction of improved reconstructions
compared to previous publications. In addition, we present the first results
from an all-sky search for extended sources of neutrinos. We update results of
searches for neutrino emission from stacked catalogs of sources, and test five
new catalogs; two of Galactic supernova remnants and three of active galactic
nuclei. In all cases, the data are compatible with the background-only
hypothesis, and upper limits on the flux of muon neutrinos are reported for the
sources considered.Comment: 36 pages, 15 figures. Submitted to the Astrophysical Journa
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