661 research outputs found
Forage herbs improve mineral composition of grassland herbage
Provision of an adequate mineral supply in the diets of ruminants fed mainly on grassland herbage can present a challenge if mineral concentrations are suboptimal for animal nutrition. Forage herbs may be included in grassland seed mixtures to improve herbage mineral content, although there is limited information about mineral concentrations in forage herbs. To determine whether herbs have greater macro- and micromineral concentrations than forage legumes and grasses, we conducted a 2-year experiment on a loamy-sand site in Denmark sown with a multi-species mixture comprised of three functional groups (grasses, legumes and herbs). Herb species included chicory (Cichorium intybus L.), plantain (Plantago lanceolata L.), caraway (Carum carvi L.) and salad burnet (Sanguisorba minor L.). We also investigated the effect of slurry application on the macro- and micromineral concentration of grasses, legumes and herbs. In general, herbs had greater concentrations of the macrominerals P, Mg, K and S and the microminerals Zn and B than grasses and legumes. Slurry application indirectly decreased Ca, S, Cu and B concentrations of total herbage because of an increase in the proportion of mineral-poor grasses. Our study indicates that including herbs in forage mixtures is an effective way of increasing mineral concentrations in herbage
Large-System Analysis of Correlated MIMO Multiple Access Channels with Arbitrary Signaling in the Presence of Interference
Presence of multiple antennas on both sides of
a communication channel promises significant improvements in
system throughput and power efficiency. In effect, a new clas
s
of large multiple-input multiple-output (MIMO) communication
systems has recently emerged and attracted both scientific and
industrial attention. To analyze these systems in realistic scenarios,
one has to include such aspects as co-channel interference,
multiple access and spatial correlation. In this paper, we study
the properties of correlated MIMO multiple-access channels in
the presence of external interference. Using the replica method
from statistical physics, we derive the ergodic sum-rate of the
communication for arbitrary signal constellations when the numbers
of antennas at both ends of the channel grow large. Based
on these asymptotic expressions, we also address the problem of
sum-rate maximization using statistical channel information and
linear precoding. The numerical results demonstrate that when
the interfering terminals use discrete constellations, the resulting
interference becomes easier to handle compared to Gaussian
signals. Thus, it may be possible to accommodate more interfering
transmitter-receiver pairs within the same area as compare
d
to the case of Gaussian signals. In addition, we demonstrate
numerically for the Gaussian and QPSK signaling schemes that it
is possible to design precoder matrices that significantly improve
the achievable rates at low-to-mid range of signal-to-noise ratios
when compared to isotropic precoding
Directed differentiation of porcine epiblast-derived neural progenitor cells into neurons and glia
AbstractNeural progenitor cells (NPCs) are promising candidates for cell-based therapy of neurodegenerative diseases; however, safety concerns must be addressed through transplantation studies in large animal models, such as the pig. The aim of this study was to derive NPCs from porcine blastocysts and evaluate their in-vitro differentiation potential. Epiblasts were manually isolated from expanded hatched blastocysts and cultured on MEF feeder cells. Outgrowth colonies were passaged to MS5 cells and rosettes were further passaged to Matrigel-coated dishes containing bFGF and EGF. Three NPC lines were established which showed expression of SOX2, NESTIN and VIMENTIN. One line was characterised in more detail, retaining a normal karyotype and proliferating for more than three months in culture. Following differentiation, TUJI was significantly up-regulated in protocol 2 (RA and SHH; 58% positive cells) as were NF and TH. In contrast, MBP was significantly up-regulated in protocol 3 (FGF8 and SHH; 63% positive cells), whereas, GFAP was significantly up-regulated in protocols 1–4 (33%, 25%, 43% and 22%). The present study provides the first report of a porcine blastocyst-derived NPC line capable of differentiating into both neurons and glia, which may be of paramount importance for future transplantation studies in large animal models of neurodegenerative diseases
Nonparametric Bayesian Mixed-effect Model: a Sparse Gaussian Process Approach
Multi-task learning models using Gaussian processes (GP) have been developed
and successfully applied in various applications. The main difficulty with this
approach is the computational cost of inference using the union of examples
from all tasks. Therefore sparse solutions, that avoid using the entire data
directly and instead use a set of informative "representatives" are desirable.
The paper investigates this problem for the grouped mixed-effect GP model where
each individual response is given by a fixed-effect, taken from one of a set of
unknown groups, plus a random individual effect function that captures
variations among individuals. Such models have been widely used in previous
work but no sparse solutions have been developed. The paper presents the first
sparse solution for such problems, showing how the sparse approximation can be
obtained by maximizing a variational lower bound on the marginal likelihood,
generalizing ideas from single-task Gaussian processes to handle the
mixed-effect model as well as grouping. Experiments using artificial and real
data validate the approach showing that it can recover the performance of
inference with the full sample, that it outperforms baseline methods, and that
it outperforms state of the art sparse solutions for other multi-task GP
formulations.Comment: Preliminary version appeared in ECML201
Linearly Polarized Modes of a Corrugated Metallic Waveguide
A linearly polarized (LP[subscript mn]) mode basis set for oversized, corrugated, metallic waveguides is derived for the special case of quarter-wavelength-depth circumferential corrugations. The relationship between the LPmn modes and the conventional modes (HEmn, EHmn, TE0n, TM0n) of the corrugated guide is shown. The loss in a gap or equivalent miter bend in the waveguide is calculated for single-mode and multimode propagation on the line. In the latter case, it is shown that modes of the same symmetry interfere with one another, causing enhanced or reduced loss, depending on the relative phase of the modes. If two modes with azimuthal (m) indexes that differ by one propagate in the waveguide, the resultant centroid and the tilt angle of radiation at the guide end are shown to be related through a constant of the motion. These results describe the propagation of high-power linearly polarized radiation in overmoded corrugated waveguides.United States. Dept. of Energy (Office of Fusion Energy Sciences)United States. Dept. of Energy (Virtual Laboratory for Technology)United States. Dept. of Energy (Office of Science, US ITER Project
Asymptotic Performance Analysis of a K-Hop Amplify-and-Forward Relay MIMO Channel
The present paper studies the asymptotic performance of multi-hop amplify-and-forward relay multiple-antenna communication channels. Each multi-antenna terminal in the network amplifies the received signal, sent by a source, and retransmits it upstream towards a destination. Achievable ergodic rates under both jointly optimal detection and decoding and practical separate decoding schemes for arbitrary signaling schemes, along with the average bit error rate for various receiver structures are derived in the regime where the number of antennas at each terminal grows large without a bound. To overcome the difficulty of averaging over channel realizations we apply large-system analysis based on the replica method from statistical physics. The validity of the large-system analysis is further verified through Monte Carlo simulations of realistic finite-sized systems
Fusion in coset CFT from admissible singular-vector decoupling
Fusion rules for Wess-Zumino-Witten (WZW) models at fractional level can be
defined in two ways, with distinct results. The Verlinde formula yields fusion
coefficients that can be negative. These signs cancel in coset fusion rules,
however. On the other hand, the fusion coefficients calculated from decoupling
of singular vectors are non-negative. They produce incorrect coset fusion
rules, however, when factorisation is assumed. Here we give two prescriptions
that yield the correct coset fusion rules from those found for the WZW models
by the decoupling method. We restrict to the Virasoro minimal models for
simplicity, and because decoupling results are only complete in the \su(2)
case.Comment: 22 pages, harvma
Low-Power Testing of Losses in Millimeter-Wave Transmission Lines for High-Power Applications
We report the measurement of small losses in transmission line (TL) components intended for high-power millimeter-wave applications. Measurements were made using two different low-power techniques: a coherent technique using a vector network analyzer (VNA) and an incoherent technique using a radiometer. The measured loss in a 140 GHz 12.7 mm diameter TL system, consisting of 1.7 m of circular corrugated waveguide and three miter bends, is dominated by the miter bend loss. The measured loss was 0.3±0.1 dB per miter bend using a VNA; and 0.22±0.1 dB per miter bend using a radiometer. Good agreement between the two measurement techniques implies that both are useful for measuring small losses. To verify the methodology, the VNA technique was employed to measure the extremely small transmission loss in a 170 GHz ITER prototype TL system consisting of three lengths of 1 m, 63.5 mm diameter, circular corrugated waveguide and two miter bends. The measured loss of 0.05±0.02 dB per miter bend may be compared with the theoretical loss of 0.027 dB per miter bend. These results suggest that low-power testing of TL losses, utilizing a small, simple TL system and a VNA, is a reliable method for evaluating performance of low-loss millimeter-wave TL components intended for use in high-power applications
On Principal Admissible Representations and Conformal Field Theory
The principal admissible representations of affine Kac-Moody algebras are
studied, with a view to their use in conformal field theory. We discuss the
generation of the set of principal admissible highest weights, concentrating
mainly on at rational level . A related algorithm is described
that produces the Malikov-Feigen-Fuchs null vectors of these representations.
With the principal admissible description of the highest weights, we are able
to prove that field identifications (including maverick ones) lead to the
canonical description of the primary fields of the nonunitary diagonal coset
theories.Comment: Harvmac (b mode : 32 p; l mode: 36 p), 5 figures, some minor
reformulations, references added and typos correcte
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