Purpose
Implantation of the mammalian embryo in the uterus is preceded by escape from the zona pellucida. In some species, hatching from the zona occurs preferentially from one or the other poles of ...the embryo. The situation for the bovine embryo, in which hatching precedes attachment to the uterus by more than a week, is unclear. The purpose was to describe whether hatching of the bovine embryo from the zona pellucida occurs preferentially from the embryonic or abembryonic pole.
Methods
Bovine blastocysts undergoing hatching were examined by light microscopy (
n
= 84) and epifluorescence imaging using antibodies for markers of epiblast, hypoblast, and trophectoderm (TE) (
n
= 26). The location of hatching was classified as being at the embryonic pole, if hatching occurred ipsilateral to the inner cell mass (ICM), or abembryonic, if hatching occurred contralateral to the ICM.
Results
A total of 55% of blastocysts exited the zona pellucida through an opening at the embryonic pole. In these cases, 68% of the cells emerging through the zona pellucida were derived from the ICM. The remainder of blastocysts hatched from an opening either contralateral or to the side of the ICM. In these cases, 87% of hatched cells were TE.
Conclusion
For the bovine embryo, there is nearly equal probability of hatching from the embryonic or abembryonic poles. Given that the surface area of the zona pellucida in contact with the TE overlying the ICM is less than for the remainder of the blastocyst, there is some preference for hatching through the embryonic pole. Thus, the bovine embryo is distinct from the mouse and human, where hatching occurs preferentially at the abembryonic pole.
ABSTRACT We use recently released solar wind compositional data to determine the metallicity of the Sun-the fraction per unit mass that is composed of elements heavier than He. We focus on a ...present-day solar sample available to us, which is the least fractionated solar wind from coronal holes near the poles of the Sun. Using these data, we derive a metallicity of Z = 0.0196 0.0014, which is significantly larger than recent published values based on photospheric spectroscopy, but consistent with results from helioseismology.
Non-self-adjoint Schrödinger operators which correspond to non-symmetric zero-range potentials are investigated. We show that various properties of (eigenvalues, exceptional points, spectral ...singularities and the property of similarity to a self-adjoint operator) are completely determined by poles of the corresponding S-matrix.
This paper examines a method of speaker verification from mixture of speech and non-speech audio signals via using pole distribution of speech signals. The poles of speech signal derived from the ...all-pole speech production model are obtained via a neural net called bagging CAN2 (competitive associative net 2) for learning efficient piecewise linear approximation of nonlinear functions. We show an analysis that poles of the mixture of two audio signals are expected to show three typical phenomena. Namely, with the change of the weight of the mixture, there will be (1) a sudden change of the number of poles, (2) a gradual change of the number of poles, and (3) novel poles not in the original signals. By means of experiments, we show that there are poles exhibiting those phenomena, and they are considered to affect the performance on speaker verification. As a performance measure of speaker verification, recall shows large decrease with the change of speech signal from unmixed to mixed, especially for the mixture with violin signal as well as with speech signal. Furthermore, precision has larger value than recall for the same dataset of mixture of audio signals. Finally, we show the usefulness of the present method in further researches.
Summary
Low‐frequency electromechanical oscillations is a topic of great concern in power system operation. Undamped oscillations reduce the power transfer capacity and can lead the system to ...blackouts. Since the 70s, synchronous generators operate with power system stabilizers that add damping torque to oscillations through the excitation system control. These controllers can have either a conventional fixed structure, composed by stages of gain and phase compensation, or a multi‐band structure (MB‐PSS), composed by three bands that correspond to a specific frequency range (low, intermediate and high frequency). In the MB‐PSS structure, each band consists of two branches based on differential filters (with a gain stage and lead‐lag blocks). This paper presents an approach based on the Newton‐Raphson method for tuning MB‐PSS for power systems taking into consideration several operating conditions to ensure robustness. The approach adjusts the controller's gains to place a set of poles into a region in the complex plane with a desired damping ratio. Firstly, the method is applied to the well‐known single‐machine infinite bus system represented by the Heffron‐Phillips model. Secondly, an application to the multimachine South‐Southeastern Brazilian power system is discussed considering different operating conditions. The convergence of the proposed approach is evaluated regarding the initial conditions, the desired damping ratio, and the set of monitored poles. Linear and nonlinear time‐domain simulations validate the designed controllers. Finally, it is shown that the computational effort required by the proposed approach is lower than the one required by a class of methods widely reported in the literature for MB‐PSS design.
A pole placement approach based on the Newton‐Raphson method is proposed for tuning multi‐band power system stabilizers.
The approach designs several controllers simultaneously in multimachine power systems taking into account a set of operating conditions to ensure robustness.
A case study considering a Brazilian system shows that the approach solves the stabilizers tuning problem with a significant reduced computational effort.
HD 142990 is a Bp-type star with a nearly dipolar surface magnetic field of kilogauss strength. Recently, Lenc et al. reported the tentative discovery of Electron Cyclotron Maser Emission (ECME) from ...this star at 200 MHz. This type of emission has been observed from only three other hot magnetic stars. In this paper, we present our observations of HD 142990 with the upgraded Giant Metrewave Radio telescope at 550-804 MHz and with the legacy GMRT at 1420 MHz near the rotational phases of the nulls of the longitudinal magnetic field. We found strong enhancements in flux density in both circular polarizations, suggesting an ECME bandwith of at least 1.2 GHz (200-1420 MHz). In one of the observation sessions, we observed enhancements with opposite circular polarizations from the same magnetic pole. This has not been reported in any other hot magnetic star known to exhibit ECME. In order to explain this unusual finding, we suggest a scenario that involves a transition of the dominant mode of ECME between the magneto-ionic modes.
We investigate the asymptotically large loop-momentum behavior of multiloop amplitudes in maximally supersymmetric ( N = 4 , 8) quantum field theories in four dimensions. We check residue-theorem ...identities among color-dressed leading singularities in N = 4 supersymmetric Yang-Mills theory to demonstrate the absence of poles at infinity of all n -point MHV amplitudes through three loops. Considering the same test for N = 8 supergravity leads us to discover that this theory does support nonvanishing residues at infinity starting at two loops, and the degree of these poles grow arbitrarily with multiplicity. This causes a tension between simultaneously manifesting ultraviolet finiteness-which would be automatic at two loops for representation obtained by color-kinematic duality-and gauge invariance-which would follow from unitarity-based methods.
This paper deals with an effective reduction method of torque ripple by adopting novel asymmetric pole structure of wound-field synchronous motor. In general, skewed pole structure of a rotor is used ...to reduce torque ripple despite decreasing an average torque. This paper introduces the design parameter of shift angle of an asymmetric pole-plate for effective elimination of torque ripple. In addition, the design can maintain the length of field winding compared with skewed pole structure, which means low copper loss in field winding and low material cost. In addition, average torque can be increased at the same input voltage over the driving region as well. The 2-D finite element method is used for the analysis of proposed model and skewed model. For the comparison of characteristics between the skewed model and proposed model, skewed pole with three steps is introduced with low torque ripple.
The S- and P- wave phase shifts of low-energy pion-nucleon scatterings are analysed using Peking University representation, in which they are decomposed into various terms contributing either from ...poles or branch cuts. We estimate the left-hand cut contributions with the help of tree-level perturbative amplitudes derived in relativistic baryon chiral perturbation theory up to Formula omitted. It is found that in Formula omitted and Formula omitted channels, contributions from known resonances and cuts are far from enough to saturate experimental phase shift data - strongly indicating contributions from low lying poles undiscovered before, and we fully explore possible physics behind. On the other side, no serious disagreements are observed in the other channels.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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