Using modern reproductive technologies such as embryo transfer and artificial insemination to improve the reproductive potential of dromedary camels

Les premiers essais ont évalué le dilueur optimum pour le sperme du dromadaire. Les éjaculats de dromadaires mâles recueillis ont été dilués à 1 :1 avec un tampon vert, du Laciphos ou du glucose de lait écrémé. Puis, un total de 300 X 106 spermatozoïdes vivants ont été inséminés dans chaque femelle dont l'ovulation avait été provoquée à l'aide de 20 pg de busereline (analogue du GnRH) administrés 24 h plus tôt. La gestation a été confirmée chez 47, 53 et 0 p. 100 des femelles inséminées avec le sperme dilué dans des dilueurs respectivement à base de tampon vert, de Laciphos et de lait écrémé. Dans la seconde expérimentation, les femelles donneuses ont subi une superovulation avec un mélange de 20 Ul de FSH porcine et 2 500 Ul de gonadotrophine chorionique équine. Les femelles répondant à ce traitement ont été accouplées à des mâles sélectionnés dès que la majorité des follicules avaient atteint 1,3 à 1,8 cm de diamètre. L'utérus était lavé sans intervention chirurgicale huit jours après l'accouplement (sept jours après l'ovulation). Les embryons collectés étaient soit directement transférés, un à la fois, chez des receveuses à différents stades de synchronisme par rapport au 7e jour de la donneuse (+1 à -3 jours, n = 58), soit réfrigérés dans un milieu de lavage spécifique pendant 24 h dans un Equitainer à 4 'C avant d'être transférés, un à la fois, chez des receveuses (n = 32) au 61 jour après l'ovulation. Le taux de gestation a augmenté jusqu'au maximum de 67 p. 100 quand la receveuse était synchronisée à 1 jour avant la donneuse. Ce taux a décru fortement quand le niveau d'asynchronie a augmenté à + 1 (9 p. 100) ou à -3 (10 p. 100). L'état de gravidité de 20 receveuses (63 p. 100) sur les 32 qui avaient reçu les embryons réfrigérés a été confirmé entre 18 et 20 jours après l'ovulation, entraînant un taux de succès similaire à celui atteint dans le groupe de contrôle qui avait reçu des embryons frais (67 p. 100). (Résumé d'auteur

Binary Collisions and the Slingshot Effect

We derive the equations for the gravity assist manoeuvre in the general 2D case without the constraints of circular planetary orbits or widely different masses as assumed by Broucke, and obtain the slingshot conditions and maximum energy gain for arbitrary mass ratios of two colliding rigid bodies. Using the geometric view developed in an earlier paper by the authors the possible trajectories are computed for both attractive or repulsive interactions yielding a further insight on the slingshot mechanics and its parametrization. The general slingshot manoeuvre for arbitrary masses is explained as a particular case of the possible outcomes of attractive or repulsive binary collisions, and the correlation between asymptotic information and orbital parameters is obtained in general.Comment: 12 pages, 7 figures, accepted for publication Dec'07, Celestial Mechanics and Dynamical Astronom

Structure and dynamics of Rh surfaces

Lattice relaxations, surface phonon spectra, surface energies, and work functions are calculated for Rh(100) and Rh(110) surfaces using density-functional theory and the full-potential linearized augmented plane wave method. Both, the local-density approximation and the generalized gradient approximation to the exchange-correlation functional are considered. The force constants are obtained from the directly calculated atomic forces, and the temperature dependence of the surface relaxation is evaluated by minimizing the free energy of the system. The anharmonicity of the atomic vibrations is taken into account within the quasiharmonic approximation. The importance of contributions from different phonons to the surface relaxation is analyzed.Comment: 9 pages, 7 figures, scheduled to appear in Phys. Rev. B, Feb. 15 (1998). Other related publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm

What are the ways do K-12 public school systems and teacher training programs contribute to the exploitation of black educators; what political, cultural and economic ends does this serve? How does the current treatment and deployment of black educators hamper rather than further black educational progress?

This Capstone Research Project: What are the ways do K-12 public school systems and teacher training programs contribute to the exploitation of black educators; what political, cultural and economic ends does this serve? How does the current treatment and deployment of black educators hamper rather than further black educational progress, is the first step into examining the K-12 teacher training programs in Minnesota and across the United States. I allege that University-based teacher training programs and school districts are in need of a reset for their rejection and racist extortion of the black educator that tends to center and reify continued educational debts that la bare to continued education failures for black boys and girls and students of color in K-12 school systems. We must also be aware of historical assumptions about black male educators created inside of teacher education training programs that surreptitiously obstruct not only the voice of the black body, but also rely too much on cookiecutter administrative-supported curricula that resists change in cultural relevancy, collaboration, program self-reflection and community engagement. Since January 2018, this researcher has reflected on this project looking into dark rooms that did not want any lights turned on. I could see both the good and bad reasons for the rejection of one’s culture, but we don\u27t understand the critical motives, but always have to question them. Teacher training programs are in the dark, there\u27s zero prospect that some kind of equal opportunity will occur anytime soon, but, the enrichment inside of differences is rarely deciphered for the benefit of new teachers and more frequently turned away. This research project and future writings will start to address some of the challenges that lay bare a system that hemorrhages institutional racism and cultural misunderstandings

Bcc 4^4He as a Coherent Quantum Solid

In this work we investigate implications of the quantum nature of bcc $^{4}$% He. We show that it is a unique solid phase with both a lattice structure and an Off-Diagonal Long Range Order of coherently oscillating local electric dipole moments. These dipoles arise from the local motion of the atoms in the crystal potential well, and oscillate in synchrony to reduce the dipolar interaction energy. The dipolar ground-state is therefore found to be a coherent state with a well defined global phase and a three-component complex order parameter. The condensation energy of the dipoles in the bcc phase stabilizes it over the hcp phase at finite temperatures. We further show that there can be fermionic excitations of this ground-state and predict that they form an optical-like branch in the (110) direction. A comparison with 'super-solid' models is also discussed.Comment: 12 pages, 8 figure

Insecticidal Control of the Sugar-Beet Root Maggot and Yield of Sugar Beets.

uploaded by Plazi from Taxodro

The G0 Experiment: Apparatus for Parity-Violating Electron Scattering Measurements at Forward and Backward Angles

In the G0 experiment, performed at Jefferson Lab, the parity-violating elastic scattering of electrons from protons and quasi-elastic scattering from deuterons is measured in order to determine the neutral weak currents of the nucleon. Asymmetries as small as 1 part per million in the scattering of a polarized electron beam are determined using a dedicated apparatus. It consists of specialized beam-monitoring and control systems, a cryogenic hydrogen (or deuterium) target, and a superconducting, toroidal magnetic spectrometer equipped with plastic scintillation and aerogel Cerenkov detectors, as well as fast readout electronics for the measurement of individual events. The overall design and performance of this experimental system is discussed.Comment: Submitted to Nuclear Instruments and Method

Data Analysis Challenges for the Einstein Telescope

The Einstein Telescope is a proposed third generation gravitational wave detector that will operate in the region of 1 Hz to a few kHz. As well as the inspiral of compact binaries composed of neutron stars or black holes, the lower frequency cut-off of the detector will open the window to a number of new sources. These will include the end stage of inspirals, plus merger and ringdown of intermediate mass black holes, where the masses of the component bodies are on the order of a few hundred solar masses. There is also the possibility of observing intermediate mass ratio inspirals, where a stellar mass compact object inspirals into a black hole which is a few hundred to a few thousand times more massive. In this article, we investigate some of the data analysis challenges for the Einstein Telescope such as the effects of increased source number, the need for more accurate waveform models and the some of the computational issues that a data analysis strategy might face.Comment: 18 pages, Invited review for Einstein Telescope special edition of GR

Star Formation and Dynamics in the Galactic Centre

The centre of our Galaxy is one of the most studied and yet enigmatic places in the Universe. At a distance of about 8 kpc from our Sun, the Galactic centre (GC) is the ideal environment to study the extreme processes that take place in the vicinity of a supermassive black hole (SMBH). Despite the hostile environment, several tens of early-type stars populate the central parsec of our Galaxy. A fraction of them lie in a thin ring with mild eccentricity and inner radius ~0.04 pc, while the S-stars, i.e. the ~30 stars closest to the SMBH (<0.04 pc), have randomly oriented and highly eccentric orbits. The formation of such early-type stars has been a puzzle for a long time: molecular clouds should be tidally disrupted by the SMBH before they can fragment into stars. We review the main scenarios proposed to explain the formation and the dynamical evolution of the early-type stars in the GC. In particular, we discuss the most popular in situ scenarios (accretion disc fragmentation and molecular cloud disruption) and migration scenarios (star cluster inspiral and Hills mechanism). We focus on the most pressing challenges that must be faced to shed light on the process of star formation in the vicinity of a SMBH.Comment: 68 pages, 35 figures; invited review chapter, to be published in expanded form in Haardt, F., Gorini, V., Moschella, U. and Treves, A., 'Astrophysical Black Holes'. Lecture Notes in Physics. Springer 201

The 22-Year Hale Cycle in cosmic ray flux: evidence for direct heliospheric modulation

The ability to predict times of greater galactic cosmic ray (GCR) fluxes is important for reducing the hazards caused by these particles to satellite communications, aviation, or astronauts. The 11-year solar-cycle variation in cosmic rays is highly correlated with the strength of the heliospheric magnetic field. Differences in GCR flux during alternate solar cycles yield a 22-year cycle, known as the Hale Cycle, which is thought to be due to different particle drift patterns when the northern solar pole has predominantly positive (denoted as qA>0 cycle) or negative (qA0 cycles than for qA0 and more sharply peaked for qA0 solar cycles, when the difference in GCR flux is most apparent. This suggests that particle drifts may not be the sole mechanism responsible for the Hale Cycle in GCR flux at Earth. However, we also demonstrate that these polarity-dependent heliospheric differences are evident during the space-age but are much less clear in earlier data: using geomagnetic reconstructions, we show that for the period of 1905 - 1965, alternate polarities do not give as significant a difference during the declining phase of the solar cycle. Thus we suggest that the 22-year cycle in cosmic-ray flux is at least partly the result of direct modulation by the heliospheric magnetic field and that this effect may be primarily limited to the grand solar maximum of the space-age