The Northern Samail Ophiolite: An Oxygen isotope, microprobe, and field study

Geological, petrological, and oxygen isotopic data are presented for 228 whole rock and mineral samples collected from a 100×20 km area of the northern Samail ophiolite in Oman. Most of these samples are from three detailed profiles through the pillow lavas, sheeted dikes, and layered gabbros of this laterally heterogeneous fragment of Cretaceous oceanic crust, down to and across the petrologic Moho. The profiles encompass a range of petrologic and tectonic styles, and each profile exhibits distinctive ^(18)/^(16)O variations compared to one another and to mid-ocean ridge basalts, as a result of pervasive seawater-hydrothermal interaction that varied in intensity along strike in the ophiolite. In general, ^(18)O depletions are observed in the layered gabbros and ^(18)O enrichments in most of the sheeted dikes and pillow lavas, similar to results previously observed in the southern part of the ophiolite (Ibra area), where ^(18)O depletions within the gabbroic section are quantitatively balanced by ^(18)O enrichments in the shallower parts of the oceanic crust. The Wadi Hilti profile, selected as an example of relatively intact crust, differs from Ibra in having more uniform and slightly higher δ^(18)O in the gabbros (+5.4 to +6.3), as well as in containing more hydrous alteration minerals (amphibole, epidote, chlorite, and prehnite). The profiles in the Wadi Kanut-Shafan and Wadi Rajmi sections are much more complex and reveal the impact of off-axis intrusions and deep crustal shearing. Plagiogranite-wehrlite intrusions in the Shafan-Kanut area superimposed a local hydrothermal aureole on the ophiolite, evident in dikes highly depleted in ^(18)O, quartz-sulfide veins, abundant epidote, thullite, and chlorite in shallower rocks, and low-temperature hydrous alteration of deeper gabbroic rocks; the latter produced an overall increase in whole rock δ^(18)O (+6.2 to +6.9). Such late stage intrusions are found throughout the northern half of the Samail ophiolite. The Wadi Rajmi area, which is a possible fossil transform or propagating rift, represents the most complex of the three profiles; it also contains the most abundant highly deformed and hydrothermally altered rocks, together with the deepest and largest zone of ^(18)O depletion yet found in any ophiolite (locally δ^(18)O < +2.0). Conduits for large volumes of high-temperature hydrothermal fluids were provided by fractures now occupied by low-^(18)O gabbro pegmatites and low-^(18)O dikes. Material balance estimates for the regional samples and from the various transects through the ophiolite give crustal bulk δ^(18)O averages (+5.9 to +6.3) that are, within sampling error, almost identical to the average MORB basalt value of about +5.8, if both vertical and lateral crustal heterogeneities are integrated into a three-dimensional model. This supports and amplifies the conclusion of earlier workers that the δ^(18)O of seawater is buffered and controlled by hydrothermal interaction with oceanic crust, as long as the cumulative effects (both spatial and temporal) of all seafloor magmatic/hydrothermal processes are considered. The very slight out-of-balance enrichment of the integrated crustal average δ^(18)O compared to MORB may be explained by the ubiquitous mineralogical and isotopic evidence for a late, low-temperature alteration event in the basal gabbros; these effects are prominent in the vicinity of the petrologic Moho and may indicate exchange with low-temperature aqueous fluids during or after detachment of the obducted slab

A polymorphism in a let-7 microRNA binding site of KRAS in women with endometriosis.

Endometriosis is found in 5-15% of women of reproductive age and is more frequent in relatives of women with the disease. Activation of KRAS results in de novo endometriosis in mice, however, activating KRAS mutations have not been identified in women. We screened 150 women with endometriosis for a polymorphism in a let-7 microRNA (miRNA) binding site in the 3'-UTR of KRAS and detected a KRAS variant allele in 31% of women with endometriosis as opposed to 5% of a large diverse control population. KRAS mRNA and protein expression were increased in cultured endometrial stromal cells of women with the KRAS variant. Increased KRAS protein was due to altered miRNA binding as demonstrated in reporter assays. Endometrial stromal cells from women with the KRAS variant showed increased proliferation and invasion. In a murine model, endometrial xenografts containing the KRAS variant demonstrated increased proliferation and decreased progesterone receptor levels. These findings suggest that an inherited polymorphism of a let-7 miRNA binding site in KRAS leads to abnormal endometrial growth and endometriosis. The LCS6 polymorphism is the first described genetic marker of endometriosis risk

Chemoattraction of bone marrow-derived stem cells towards human endometrial stromal cells is mediated by estradiol regulated CXCL12 and CXCR4 expression

AbstractBone marrow derived cells engraft to the uterine endometrium and contribute to endometriosis. The mechanism by which these cells are mobilized and directed to the endometrium has not been previously characterized. We demonstrate that human endometrial stromal cells (hESCs) produce the chemokine CXCL12 and that bone marrow cells (BMCs) express the CXCL12 receptor, CXCR4. Treatment with physiological levels of estradiol (E2) induced both CXCL12 and CXCR4 expression in hESCs and BMCs, respectively. BMCs migrated towards hESCs conditioned media; a CXCR4 antagonist blocked migration indicating that CXCL12 acting through its receptor, CXCR4, is necessary for chemoattraction of BM cells to human endometrial cells. E2 increased both CXCL12 expression in endometrial cells and CXCR4 expression in BM cells, further enhancing chemoattraction. E2 induced CXCL12/CXCR4 expression in endometrium and BM, respectively, drives migration of stem cells to the endometrium. The E2-CXCL12/CXCR4 signaling pathway may be useful in determining treatments for endometrial disorders, and may be antagonized to block stem cell migration to endometriosis

Update in hormone therapy use in menopause

The original report from the Women&apos;s Health Initiative (WHI) changed our understanding of the benefits and risks of hormone therapy. Since that time, reanalysis of the WHI and additional data from other studies have further refined these concepts. Here we provide an update on recent advances in the field. Menopausal hormone therapy continues to have a clinical role in the management of vasomotor symptoms. However, our understanding of the role of hormones in cardiovascular disease and breast cancer continues to evolve. Further analyses of the effect of age and proximity to menopause at the time of initiation of therapy, duration of treatment, dose, route of administration, and the persistence of risks and benefits after stopping hormone therapy are described. In addition, recent data have emerged suggesting that there may be a link between hormone therapy and cancers of the lung and ovary. Finally, we discuss new advances in hormone therapy that will likely lead to a more favorable benefit-to-risk ratio, enabling safer effective menopausal symptom relief. O ver the past several decades, a large number of observational studies suggested that the use of hormone therapy in menopause not only relieved vasomotor symptoms, but also reduced the risk of several chronic medical conditions such as osteoporosis and cardiovascular disease. However, in 2002, the results of a prospective randomized trial, the Women&apos;s Health Initiative (WHI), demonstrated that many of the benefits identified in observational studies were not present in a population randomized to treatment; some hypothesized that the previously purported benefits may have been due not to the therapy but rather to confounding and selection biases, as well as other methodological limitations. In response to the findings of the WHI and other randomized trials, menopausal hormone therapy (MHT) use declined dramatically. The WHI confirmed a decreased risk of osteoporosis and fractures in menopausal women assigned to hormone therapy; it also confirmed an increased risk of breast cancer previously identified in women who use combination estrogen plus progestin (E ϩ P) hormone therapy. However, the WHI trial also revealed that women assigned to MHT had an increase in coronary disease, stroke, and venous thromboembolic events. In the past few years, there has been renewed interest in the risks of MHT, especially that of breast cancer as well as the apparent elevation, rather than reduction, in the risk of coronary events. Since the original publication of the WHI results in 2002, a large number of subsequent studies have looked at these concepts in detail. In addition, recent data have emerged suggesting that there may be a link between hormone therapy and cancers of the lung and ovary. Further analyses of the effect of age and proximity to menopause at the time of initiation of therapy, duration of treatment, dose, route of administration, and the persistence of risks and benefits after stopping hormone therapy have all recently been described. Here we provide an overview of recent developments in this field, including the central role of timing of initiation. Coronary Heart Disease (CHD) The original report from the WHI demonstrated that women randomized to conjugated equine estrogens (CEEs) combined with medroxyprogesterone acetat

A major radio outburst in III Zw 2 with an extremely inverted, millimeter-peaked spectrum

III Zw 2 is a spiral galaxy with an optical spectrum and faint extended radio structure typical of a Seyfert galaxy, but also with an extremely variable, blazar-like radio core. We have now discovered a new radio flare where the source has brightened more than twenty-fold within less than two years. A broad-band radio spectrum between 1.4 and 666 GHz shows a textbook-like synchrotron spectrum peaking at 43 GHz, with a self-absorbed synchrotron spectral index +2.5 at frequencies below 43 GHz and an optically thin spectral index -0.75 at frequencies above 43 GHz. The outburst spectrum can be well fitted by two homogenous, spherical components with equipartition sizes of 0.1 and 0.2 pc at 43 and 15 GHz, and with magnetic fields of 0.4 and 1 Gauss. VLBA observations at 43 GHz confirm this double structure and these sizes. Time scale arguments suggest that the emitting regions are shocks which are continuously accelerating particles. This could be explained by a frustrated jet scenario with very compact hotspots. Similar millimeter-peaked spectrum (MPS) sources could have escaped our attention because of their low flux density at typical survey frequencies and their strong variability.Comment: ApJ Letters, in press, (AAS)LaTeX, 3 figures, available at http://www2.mpifr-bonn.mpg.de/staff/hfalcke/publications.html#iiizw2 or in a few weeks at http://www.mpifr-bonn.mpg.de/staff/falcke/publications.html#iiizw

Enhancing spaceflight safety with UOS3 cubesat

Earth orbits are becoming increasingly congested. This will not only impact future space operations but also become a concern for the population on the ground; with more spacecraft being flown, more objects will re-enter the atmosphere in an uncontrolled fashion. Parts of these satellites can reach Earth surface and endanger the ground population (e.g. ROSAT or UARS satellites). A student-run project from the University of Southampton aims to build a 1U cubesat (approx. 10 by 10 by 10 cm satellite), which will gather data that will improve the accuracy of re-entry predictions. The cubesat will record and deliver its position and attitude during the orbital decay, thus providing validation data for re-entry prediction tools. This will reduce the risk to the ground population because more accurate prognoses will allow mitigation measures to be implemented in the areas at risk. The mission could also allow the risk of collision between spacecraft to be estimated more accurately thanks to improvement of the atmospheric models. This would give the decision makers more complete information to use, for instance, in collision avoidance manoeuvre plannin