8,881 research outputs found
Efficient Production of Large 39K Bose-Einstein Condensates
We describe an experimental setup and the cooling procedure for producing 39K
Bose-Einstein condensates of over 4x10^5 atoms. Condensation is achieved via a
combination of sympathetic cooling with 87Rb in a
quadrupole-Ioffe-configuration (QUIC) magnetic trap, and direct evaporation in
a large volume crossed optical dipole trap, where we exploit the broad Feshbach
resonance at 402 G to tune the 39K interactions from weak and attractive to
strong and repulsive. In the same apparatus we create quasi-pure 87Rb
condensates of over 8x10^5 atoms.Comment: 7 pages, 5 figures; figure font compatibility improve
Application of design science research to design a modelling approach for procurement of infrastructure systems
© 2019 IEEE. Model-driven approaches are widely used in managing the complex domains such as infrastructure systems or disaster management. The foundation of conducting a systematic research is designing a methodology that pertinently covers the steps of research from problem definition to solution proposal and then identifying or tailoring a method for developing and validating the solution. This paper explains the application of Design Science for conducting a research which aims at providing a model-driven approach for addressing the complexities of infrastructure procurement projects. So firstly the design science artefacts are adopted for designing the method for this research. Then the steps of this method are explained briefly along with description of how each step is applied in this research. The core of this method is proposing a process for developing and validating the metamodels which is designed based on combination of other metamodeling processes
Identification of critical amino acids involved in α1-β interaction in voltage-dependent Ca2+ channels
AbstractIn voltage-dependent Ca2+ channels, the α1 and β subunits interact via two cytoplasmic regions defined as the Alpha Interaction Domain (AID) and Beta Interaction Domain (BID). Several novel amino acids for that interaction have now been mapped in both domains by point mutations. It was found that three of the nine amino acids in AID and four of the eight BID amino acids tested were essential for the interaction. Whereas the important AID amino acids were clustered around five residues, the important BID residues were more widely distributed within a larger 16 amino acid sequence. The affinity of the AIDA GST fusion protein for the four interacting β1b BID mutants was not significantly altered compared with the wild-type β1b despite the close localization of mutated residues to disruptive BID amino acids. Expression of these interactive β mutants with the full-length α1A subunit only slightly modified the stimulation efficiency when compared with the wild-type β1b subunit. Our data suggest that non-disruptive BID sequence alterations do not dramatically affect the β subunit-induced current stimulation
Identification of QTL Controlling Thermal Properties of Maize Starch
Starch has many uses and some of these uses would be facilitated by altering its thermal properties. Genetic manipulation of starch thermal properties will be facilitated by a better understanding of the genetic control of starch gelatinization. We used differential scanning calorimetry to characterize the gelatinization parameters of maize (Zea mays L.) kernel starch prepared from two populations of recombinant inbred lines, an intermated B73xMo17 population (IBM) and an F6:7 Mo17xH99 population. The traits examined were the onset and peak temperatures of gelatinization and the enthalpy of gelatinization. These traits were measured for both native starch and for gelatinized starch allowed to recrystallize, a process called retrogradation. Substantial variation in these traits was found in spite of the narrow genetic base of the populations. We identified several quantitative trait loci (QTL) controlling traits of interest in each population. In the IBM population, a significant QTL for the peak temperature of gelatinization of retrograded starch co-localized to a molecular marker in the Wx1 gene, which encodes a granule bound starch synthase. The major QTL identified in this study explain, on average, ≈15% of the variation for a given trait, underscoring the complexity of the genetic control of starch functional properties
Can a Bose gas be saturated?
Bose-Einstein condensation is unique among phase transitions between
different states of matter in the sense that it occurs even in the absence of
interactions between particles. In Einstein's textbook picture of an ideal gas,
purely statistical arguments set an upper bound on the number of particles
occupying the excited states of the system, and condensation is driven by this
saturation of the quantum vapour. Dilute ultracold atomic gases are celebrated
as a realisation of Bose-Einstein condensation in close to its purely
statistical form. Here we scrutinise this point of view using an ultracold gas
of potassium (39K) atoms, in which the strength of interactions can be tuned
via a Feshbach scattering resonance. We first show that under typical
experi-mental conditions a partially condensed atomic gas strongly deviates
from the textbook concept of a saturated vapour. We then use measurements at a
range of interaction strengths and temperatures to extrapolate to the
non-interacting limit, and prove that in this limit the behaviour of a Bose gas
is consistent with the saturation picture. Finally, we provide evidence for the
universality of our observations through additional measurements with a
different atomic species, 87Rb. Our results suggest a new way of characterising
condensation phenomena in different physical systems.Comment: 6 pages, 5 figure
Giving voters what they want? Party orientation perceptions and preferences in the British electorate
Some of the most important propositions in the political marketing literature hinge on assumptions about the electorate. In particular, voters are presumed to react in different ways to different orientations or postures. Yet there are theoretical reasons for questioning some of these assumptions, and certainly they have seldom been empirically tested. Here, we focus on one prominent example of political marketing research: Lees-Marshment’s orientations’ model. We investigate how the public reacts to product and market orientation, whether they see a trade-off between the two (a point in dispute among political marketing scholars), and whether partisans differ from non-partisan voters by being more inclined to value product over market orientation. Evidence from two mass sample surveys of the British public (both conducted online by YouGov) demonstrates important heterogeneity within the electorate, casts doubt on the core assumptions underlying some political marketing arguments and raises broader questions about what voters are looking for in a party
Condensation dynamics in a quantum-quenched Bose gas
By quenching the strength of interactions in a partially condensed Bose gas
we create a "super-saturated" vapor which has more thermal atoms than it can
contain in equilibrium. Subsequently, the number of condensed atoms ()
grows even though the temperature () rises and the total atom number decays.
We show that the non-equilibrium evolution of the system is isoenergetic and
for small initial observe a clear separation between and
dynamics, thus explicitly demonstrating the theoretically expected "two-step"
picture of condensate growth. For increasing initial values we observe a
crossover to classical relaxation dynamics. The size of the observed
quench-induced effects can be explained using a simple equation of state for an
interacting harmonically-trapped atomic gas.Comment: 4 pages, 4 figure
A recent whole-genome duplication divides populations of a globally-distributed microsporidian
The Microsporidia are a major group of intracellular fungi and important parasites of animals including insects, fish, and immunocompromised humans. Microsporidian genomes have undergone extreme reductive evolution but there are major differences in genome size and structure within the group: some are prokaryote-like in size and organisation (<3 Mb of gene-dense sequence) while others have more typically eukaryotic genome architectures. To gain fine-scale, population-level insight into the evolutionary dynamics of these tiny eukaryotic genomes, we performed the broadest microsporidian population genomic study to date, sequencing geographically isolated strains of Spraguea, a marine microsporidian infecting goosefish worldwide. Our analysis revealed that population structure across the Atlantic Ocean is associated with a conserved difference in ploidy, with American and Canadian isolates sharing an ancestral whole genome duplication that was followed by widespread pseudogenisation and sorting-out of paralogue pairs. While past analyses have suggested de novo gene formation of microsporidian-specific genes, we found evidence for the origin of new genes from noncoding sequence since the divergence of these populations. Some of these genes experience selective constraint, suggesting the evolution of new functions and local host adaptation. Combining our data with published microsporidian genomes, we show that nucleotide composition across the phylum is shaped by a mutational bias favoring A and T nucleotides, which is opposed by an evolutionary force favoring an increase in genomic GC content. This study reveals ongoing dramatic reorganization of genome structure and the evolution of new gene functions in modern microsporidians despite extensive genomic streamlining in their common ancestor
Resistant Starch and Starch Thermal Characteristics in Exotic Corn Lines Grown in Temperate and Tropical Environments
Corn as a food that is heated and cooled to allow starch retrogradation has higher levels of resistant starch (RS). Increasing the amount of RS can make corn an even healthier food and may be accomplished by breeding and selection, especially by using exotic germplasm. Sixty breeding lines of introgressed exotic germplasm backgrounds, selected for high yield, were grown in three tropical and temperate locations and analyzed for starch thermal characteristics and RS levels. Although actual values for all starch characteristics were within normal levels, most characteristics had significant genotypic effects, and all had significant location effects. Thermal properties of retrograded starch were more influenced by the environment than the thermal properties of raw starch, making retrograded starch traits more heritable than raw starch traits. This suggests that a breeding strategy based on retrograded starch traits will have a better chance of success than a breeding strategy based on raw starch traits. A significant genotype effect for RS levels indicates that genotypic selection to raise the level of RS and increase the healthful aspects of corn food should be successful. Significant location effects indicate that breeders using winter nurseries to accelerate their breeding progress need to be careful when making selections using RS data collected on seed grown in the tropics. A small but highly significant correlation between RS and some thermal characteristics, especially percentage of retrogradation, indicates that we may be able to select promising genotypes for RS selection based on our extensive database of thermal characteristics collected on a wide number of diverse corn lines
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