Establishment and maintenance of pregnancy results from signaling by the conceptus (embryo/fetus and associated extraembryonic membranes) and requires progesterone produced by the corpus luteum (CL). In most mammals, hormones produced by the trophoblast maintain progesterone production by acting directly or indirectly to maintain the CL. In domestic animals (ruminants and pigs), hormones from the trophoblast are antiluteolytic in that they act on the endometrium to prevent uterine release of luteolytic prostaglandin F2 alpha (PGF). In cyclic and pregnant sheep, progesterone negatively autoregulates expression of the progesterone receptor (PR) gene in the endometrial luminal (LE) and superficial glandular epithelium (GE). Available evidence in cyclic sheep indicates that loss of the PR is closely followed by increases in epithelial estrogen receptors (ER) and then oxytocin receptors (OTR), allowing oxytocin to induce uterine release of luteolytic PGF pulses. In pregnant sheep, the conceptus trophoblast produces interferon tau (IFN tau) that acts on the endometrium to inhibit transcription of the ER alpha gene directly and the OTR gene indirectly to abrogate development of the endometrial luteolytic mechanism. Subsequently, sequential, overlapping actions of progesterone, IFN tau, placental lactogen (PL) and growth hormone (GH) comprise a hormonal servomechanism that regulates endometrial gland morphogenesis and terminal differentiated function to maintain pregnancy in sheep. In pigs, the conceptus trophoblast produces estrogen that alters the direction of PGF secretion from an endocrine to exocrine direction, thereby sequestering luteolytic PGF within the uterine lumen. Conceptus estrogen also increases expression of fibroblast growth factor 7 (FGF-7) in the endometrial LE that, in turn, stimulates proliferation and differentiated functions of the trophectoderm, which expresses the FGF-7 receptor. Strategic manipulation of these physiological mechanisms can offer therapeutic schemes to improve uterine capacity, conceptus survival and reproductive health.

Small amounts of water have previously been found to have a dramatic effect on the value of the seismic dissipation factor Q-•. This suggests the importance of controlling the environment in which Q-i measurements are made. Since the effect of moisture is so large, studying the variation in Q-i with partial pressure of water and other volatiles can provide important clues for understanding the attenuation mechanisms in 'room dry' rocks. Thus measurements have been made of both Q-• and velocity for several limestones (all >99% CaCO3) and sandstones. The Q-i of both limestones and sandstones is affected by the presence of water vapor, but at any given partial pressure of water (P•2o) the Q-i of the limestones is lower than the Q-i of the sandstones. Velocities of the sandstones decreased by as much as 30% as the relative humidity was changed from 0 to 80%. Velocities of limestones of comparable porosity decreased only 2% over the same range. Simultaneously with the Q-i and velocity measurements, adsorption isotherms (-•23øC) were measured on a companion sample. Generally, limestones adsorbed less water at a given partial pressure than the sandstones. The amount of water adsorbed, at most 2-3 mg/g, does not increase the density enough to account for the decrease in velocity, particularly in the sandstones. The Brunauer-Emmett-Teller equation was used to calculate surface areas from the adsorption isotherms. Surface areas ranged from 0.5 to 3.4 m2/g. Limestones had lower surface areas than the sand stones. The larger surface areas in the sandstones can probably be attributed to varying amounts of clays.A plot of Q-i versus mass adsorbed shows that most of the increase in dissipation is associated with the adsorption of the first two monolayers of water. A fixed amount of water causes a greater change in the Q-i of the sandstones than of the limestones. One sandstone was measured by using anhydrous benzene as the adsorbate. In contrast to the action of the water, Q-i changed very little with increased benzene pressure for small P/Po, even though significant amounts of benzene were adsorbed. For P/Po greater than 0.7, there were significant increases in Q-•. It appears that there are two mechanisms of attenuation in 'dry' rocks: one is observed at low P/Po and is associated with surface effects that are strongly dependent on the nature of the adsorbate, and the other is observed at high P/Po and is associated with fluid flow in fine pores. [] [] ß ß [] ß [] o ß ß ß ß II ß ß e © © ß 0¾ , , ' 01 ' '

The basic problems encountered in extracting estimates of seismic dissipation from data recorded on vertical seismic profiles are analyzed. Because anomalous dissipation in the subsurface is likely to be associated with conditions or lithologies of limited vertical extent, a knowledge of the factors which influence the spatial resolution of an attenuation measurement is of considerable importance. By introducing a statistical perspective, it is possible to simulate multiple measurements in an inhomogeneous interval and to draw conclusions which apply to an entire class of impedance structures. Theoretical seismograms are analyzed to demonstrate that for small receiver separations neither a single measurement nor the mean value determined from multiple measurements is likely to give a good estimate of the attenuation for an inhomogeneous depth interval. For small receiver separations, the attenuation computed from the amplitude ratios method is much more strongly influenced by the local stratigraphy in the immediate vicinity of the seismometer than by the attenuation in the depth interval between seismometers. As the seismometer separation increases, there is a dramatic decrease in the variability in the attenuation values determined from multiple measurements. A critical distance can be defined which is a measure of the spatial resolution. Beyond the critical distance the mean value approaches a quantity which is the sum of two components: the effective dissipation for an inhomogeneous interval and a stratigraphic term which describes the attenuation in a nondissipative system.

This report presents measurements of the specific dissipation factor Q−1s of rocks containing small amounts of volatiles. Q−1s was measured for shear waves as a function of relative partial pressure P/P0 for benzene, hexane, ethanol, methanol, and water. The measurements were carried out at about 10 kHz with the vibrating bar technique in a chamber in which the relative partial volatile pressure P/P0 was varied between almost zero and about 0.9. The results revealed that in the regime of one‐ or two‐monolayer coverage of absorbed volatiles, Q−1s increased dramatically with exposure to the alcohols and water but only negligibly with exposure to the hexane and benzene. The slopes of Q−1 versus monolayer coverage appeared to correlate with the dipole moment per unit volume of the volatiles. These data are presented in the context of previous measurements, which showed that the influence of volatiles on Q−1 persist to high levels of outgassing (1×10−10 torr vacuum), to elevated hydrostatic confining pressures (at least 0.5 kbar), and for a variety of crystalline rocks including terrestrial analogs of lunar basalt. Both direct (ellipsometry data) and indirect evidence (absorption isotherm data) are presented for the presence of thin films of adsorbed volatiles at low partial vapor pressures. Finally, the measurements are discussed and interpreted in terms of a physical model relating Q−1 to the relative mass of the adsorbed volatiles, the surface area of the rock, the heat of desorption of the volatile, and the rock temperature.

A new algorithm is developed for estimating the moveout velocities and polarization states in mixed wavefields recorded on multicomponent array data in the presence of random noise. The algorithm is applicable to a spatial and temporal data window in which more than two events are present. Three fundamental attributes of the waves are determined: polarization angle, apparent slowness, and the change in amplitude between adjacent detectors. In implementing the method, it is assumed that data is recorded at equispaced geophones located in a spatial window in which the three parameters are constant. Robustness is achieved by averaging the transfer matrix over all combinations of the subarrays that have the same transfer matrix. Application of a least‐squares criterion reduces the mathematics to an eigenvalue problem. The eigenvalues are complex, and their magnitude determines the amplitude change factor. The phase is a linear function of frequency with slope that determines the vertical slowness. The eigenvectors are the polarizations. The input data consists of the cross‐power spectra between subarrays that contain the same number of elements and are shifted by zero or one geophone separation. Examples illustrate the application of the algorithm to synthetic data. Numerical test results show that the performance of the method is not sensitive either to the time overlap between events or to the degree of similarity between waveforms.