4,110 research outputs found
Chiral effective field theory beyond the power-counting regime
Novel techniques are presented, which identify the chiral power-counting
regime (PCR), and realize the existence of an intrinsic energy scale embedded
in lattice QCD results that extend outside the PCR. The nucleon mass is
considered as a benchmark for illustrating this new approach. Using
finite-range regularization, an optimal regularization scale can be extracted
from lattice simulation results by analyzing the renormalization of the low
energy coefficients. The optimal scale allows a description of lattice
simulation results that extend beyond the PCR by quantifying and thus handling
any scheme-dependence. Preliminary results for the nucleon magnetic moment are
also examined, and a consistent optimal regularization scale is obtained. This
indicates the existence of an intrinsic scale corresponding to the finite size
of the source of the pion cloud.Comment: 6 pages, 4 figures, conferenc
The Relative Accuracy of Estimating the Production of Dairy Cows as Affected by Length of Testing Interval and Method of Estimating Production
Production records for dairy cows were first based on the yield of butter for a seven day period any time during the lactation. Later, 365- day records based on production for one day in each calendar month came into general use. The records preferred at present are 305- day records based on monthly test day production, but calculated using the centering date method. The centering date estimate is based on milk and butterfat production from two consecutive milkings per month. The sampling day is centered as nearly as possible in the test month period which need not coincide with the calendar month.
The reason for the general acceptance of the 305- day records is the desire of the dairyman to freshen the dairy cow annually, which means milking for ten months and dry for two months. Records calculated by the centering date method more nearly represent actual production than records calculated by other methods that have been used.
It is generally accepted that if the present testing program is used properly it can be of great value to the dairy farmer from the standpoint of herd improvement and for selecting animals for a breeding program. However, only a small percentage of the dairymen take advantage of a testing program. One of the limiting factors has been the cost of testing and record keeping. It has been suggested that bimonthly or trimonthly test periods might provide as much information as the monthly testing interval and at the same time reduce the cost to the individual dairymen. It is reasonable to speculate that with reduced costs there would be an increased number of herds tested. This would help compensate the testing supervisor and data processing center for lost income resulting from less frequent testing, and at the same time provide more information for national sire proving programs.
However, bimonthly or trimonthly testing have not been accepted because of the possiblilty of larger error being involved in individual records. This larger error occurs because the curvelinear shape of the lactation is not taken into account and a cow is given credit for the same production over the entire testing period, resulting in either under or over estimation of the record.
Tho objective of this study is to measure the relative accuracy of estimating 305- day production of dairy cows by using different testing intervals and different methods to estimate production. Monthly, bimonthly, and trimonthly intervals are studied. Methods include the centering date method and three methods using factors designed to extend production from each test day to a 305-day estimate with the test day estimate averaged to determine the final estimate of production for 305 days
Neonatal weight loss in breast and formula-fed infants
We have observed an increase in the number of breast fed babies presenting with dehydration and/or failure to thrive because of lactation failure and non-recognition of feeding problems. Recent reports1,2 support this experience and recommend monitoring of the weight of infants through the neonatal period. However, these reports acknowledge uncertainty as to what actually constitutes normal neonatal weight loss. Maisels and colleagues published two studies which have been quoted as giving guidance on normal loss. Both studies were designed primarily to study factors that influence breast milk jaundice. The first3 reported a mean weight loss of about 6% in 100 unselected well babies during the first 3 days. The subsequent study4 reported a mean weight loss of 6.86% in 186 infants. The timescale over which babies were weighed was not clearly indicated, although it may have only been 2-3 days. The sample was neither population based nor randomly selected, being largely preselected because of the presence of more pronounced jaundice. The distribution of data points for early neonatal weight loss are likely to be skewed, yet both studies reported the results as mean (SD). Owing to the design and method of data presentation, these studies cannot reliably inform the debate as to what constitutes the norm. Marchini and colleagues published reports also designed primarily to study other issues. One5 indicated a mean early weight loss of 5.7%. Measurements were recorded over a three day period, and no indication is given of the skewness of the data. Another study6 reported a median weight loss of about 6% recorded over a four day period. At least one baby lost > 15% of his/her birth weight during this time, but there is no clear information as to the frequency with which more extreme degrees of weight loss are observed
Efficient operators for studying higher partial waves
An extended multi-hadron operator is developed to extract the spectra of
irreducible representations in the finite volume. The irreducible
representations of the cubic group are projected using a coordinate-space
operator. The correlation function of this operator is computationally
efficient to extract lattice spectra. In particular, this new formulation only
requires propagator inversions from two distinct locations, at fixed physical
separation. We perform a proof-of-principle study on a lattice
volume with ~MeV by isolating the spectra of ,
and of the system with isospin-2 in the rest frame.Comment: 8 pages, 3 figures, Contribution to the conference Lattice201
Lattice QCD Evidence that the Lambda(1405) Resonance is an Antikaon-Nucleon Molecule
For almost 50 years the structure of the Lambda(1405) resonance has been a
mystery. Even though it contains a heavy strange quark and has odd parity, its
mass is lower than any other excited spin-1/2 baryon. Dalitz and co-workers
speculated that it might be a molecular state of an antikaon bound to a
nucleon. However, a standard quark-model structure is also admissible. Although
the intervening years have seen considerable effort, there has been no
convincing resolution. Here we present a new lattice QCD simulation showing
that the strange magnetic form factor of the Lambda(1405) vanishes, signaling
the formation of an antikaon-nucleon molecule. Together with a Hamiltonian
effective-field-theory model analysis of the lattice QCD energy levels, this
strongly suggests that the structure is dominated by a bound antikaon-nucleon
component. This result clarifies that not all states occurring in nature can be
described within a simple quark model framework and points to the existence of
exotic molecular meson-nucleon bound states.Comment: Manuscript accepted for publication. 4 figures, 5 page
Distributions of microplastics and larger anthropogenic debris in Norfolk Canyon, Baltimore Canyon, and the adjacent continental slope (Western North Atlantic Margin, USA)
Improved determination of hadron matrix elements using the variational method
The extraction of hadron form factors in lattice QCD using the standard two-
and three-point correlator functions has its limitations. One of the most
commonly studied sources of systematic error is excited state contamination,
which occurs when correlators are contaminated with results from higher energy
excitations. We apply the variational method to calculate the axial vector
current gA and compare the results to the more commonly used summation and
two-exponential fit methods. The results demonstrate that the variational
approach offers a more efficient and robust method for the determination of
nucleon matrix elements.Comment: 7 pages, 6 figures, talk presented at Lattice 2015, PoS (LATTICE2015
Quantum Entanglement in the Two Impurity Kondo Model
In order to quantify quantum entanglement in two impurity Kondo systems, we
calculate the concurrence, negativity, and von Neumann entropy. The
entanglement of the two Kondo impurities is shown to be determined by two
competing many-body effects, the Kondo effect and the
Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, . Due to the
spin-rotational invariance of the ground state, the concurrence and negativity
are uniquely determined by the spin-spin correlation between the impurities. It
is found that there exists a critical minimum value of the antiferromagnetic
correlation between the impurity spins which is necessary for entanglement of
the two impurity spins. The critical value is discussed in relation with the
unstable fixed point in the two impurity Kondo problem. Specifically, at the
fixed point there is no entanglement between the impurity spins. Entanglement
will only be created (and quantum information processing (QIP) be possible) if
the RKKY interaction exchange energy, , is at least several times larger
than the Kondo temperature, . Quantitative criteria for QIP are given in
terms of the impurity spin-spin correlation.Comment: 7 pages, 3 figures, 1 tabl
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