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The cohesin complex holds sister chromatids together and is essential for chromosome segregation. Recently, cohesins have been implicated in transcriptional regulation and insulation through genome-wide colocalization with the insulator protein CTCF, including involvement at the imprinted H19/Igf2 locus. CTCF binds to multiple imprinted loci and is required for proper imprinted expression at the H19/Igf2 locus. Here we report that cohesins colocalize with CTCF at two additional imprinted loci, the Dlk1-Dio3 and the Kcnq1/Kcnq1ot1 loci. Similar to the H19/Igf2 locus, CTCF and cohesins preferentially bind to the Gtl2 differentially methylated region (DMR) on the unmethylated maternal allele. To determine the functional importance of the binding of CTCF and cohesins at the three imprinted loci, CTCF and cohesins were depleted in mouse embryonic fibroblast cells. The monoallelic expression of imprinted genes at these three loci was maintained. However, mRNA levels for these genes were typically increased; for H19 and Igf2 the increased level of expression was independent of the CTCF-binding sites in the imprinting control region. Results of these experiments demonstrate an unappreciated role for CTCF and cohesins in the repression of imprinted genes in somatic cells.

Culture systems that support development and maturation of oocytes in vitro with a high efficiency would have great impact not only on research addressed at underlying mechanisms of oocyte development but also on preservation of fertility. Recently, attention has turned to using culture systems that preserve follicle integrity, in contrast to existing systems that do not maintain follicle integrity, with the hope of improving oocyte development. We report that an alginate-based follicle culture system supports both follicular and oocyte growth in vitro, with little effect on the oocyte transcriptome. Nevertheless, oocytes obtained from these follicles exhibit an increased incidence of defects in spindle formation and chromosome alignment as well as pronounced abnormalities in cortical granule biogenesis. Developmental competence is also highly compromised, because few matured oocytes develop into 1-cell embryos with pronuclei. This situation contrasts with a high incidence of pronuclear formation following development using an existing in vitro culture system that does not preserve follicle integrity.

Messenger RNA is remarkably stable during oocyte growth, thus enabling mRNAs to accumulate during the growth phase and thereby provide mRNAs that support early embryonic development. MSY2, a germ cell-specific RNA-binding protein, is implicated in regulating mRNA stability. MSY2 is essential for development because female Msy2 � /� mice are infertile. We describe here the characterization of Msy2 � /� oocytes. Mutant oocytes grow more slowly during the first wave of folliculogenesis, and maturation to and arrest at metaphase II is severely compromised because of aberrant spindle formation and chromosome congression. Consistent with MSY2 conferring mRNA stability is that the amount of poly(A)-containing RNA is reduced by ;25% in mutant oocytes. Stability of an exogenous mRNA injected into mutant oocytes is lower than when compared to their wild-type counterparts, and moreover, expression of wild-type MSY2 in mutant oocytes increases mRNA stability, whereas injection of a mutant form of MSY2 not capable of binding RNA does not. Transcription quiescence that normally occurs during the course of oocyte growth is not observed in mutant oocytes, and the transcriptome of mutant oocytes is markedly perturbed. These results, and those of previous studies, strongly implicate a central role of MSY2 in regulating mRNA stability. gene expression, histone modifications, meiotic maturation, mRNA stability, oocyte development

Riparian buffers are designed as management practices to increase infiltration and reduce surface runoff and transport of sediment and nonpoint source pollutants from crop fields to adjacent streams. Achieving these ecosystem service goals depends, in part, on their ability to remove water from the soil via transpiration. In these systems, edges between crop fields and trees of the buffer systems can create advection processes, which could influence water use by trees. We conducted a field study in a riparian buffer system established in 1994 under a humid temperate climate, located in the Corn Belt region of the Midwestern U.S. (Iowa). The goals were to estimate stand level transpiration by the riparian buffer, quantify the controls on water use by the buffer system, and determine to what extent advective energy and tree position within the buffer system influence individual tree transpiration rates. We primarily focused on the water use response (determined with the Heat Ratio Method) of one of the dominant species (Acer saccharinum) and a subdominant (Juglans nigra). A few individuals of three additional species (Quercus bicolor, Betula nigra, Platanus occidentalis) were monitored over a shorter time period to assess the generality of responses. Meteorological stations were installed along a transect across the riparian buffer to determine the microclimate conditions. The differences found among individuals were attributed to differences in species sap velocities and sapwood depths, location relative to the forest edge and prevailing winds and canopy exposure and dominance. Sapflow rates for A. saccharinum trees growing at the SE edge (prevailing winds) were 39% greater than SE interior trees and 30% and 69% greater than NW interior and edge trees, respectively. No transpiration enhancement due to edge effect was detected in the subdominant J. nigra. The results were interpreted as indicative of advection effects from the surrounding crops. Further, significant differences were document in sapflow rates between the five study species, suggesting that selection of species is important for enhancing specific riparian buffer functions. However, more information is needed on water use patterns among diverse species growing under different climatic and biophysical conditions to assist policy and management decisions regarding effective buffer design.

Multiple sets of compaction bands of southwestern Utah occur in Navajo Sandstone near a bend in the adjacent East Kaibab monocline. Forward mechanical models of blind-thrust fault deformation are used in this paper to investigate the spatial relationship between compaction bands and fault-related folding. Results are consistent with the East Kaibab monocline being underlain by a west-dipping blind high-angle reverse fault between ~ 1.5 and 5 km depth below the top of the Navajo Sandstone. Reverse slip along this reactivated fault during the Laramide orogeny is inferred to have produced values of compactional normal strain that were largest in the footwall near the concave map-view bend in the monocline. The calculated compactional normal strains and Coulomb stress increases are consistent with the field occurrence of pure and shear-enhanced compaction bands in this area. Bends, relays, stepovers, or other geometric complexities above blind reverse faults are thus inferred to be potential sites for compaction band localization in appropriate rock types.

Faults provide a record of a planet’s crustal stress state and interior dynamics, including volumetric changes related to long-term cooling. Previous work has suggested that Mars experienced a pulse of large-scale global contraction during Hesperian time. Here we evaluate the evidence for martian global contraction using a recent compilation of thrust faults. Fault-related strains were calculated for wrinkle ridges and lobate scarps to provide lower and upper bounds, respectively, on the magnitude of global contraction from contractional structures observed on the surface of Mars. During the hypothesized pulse of global contraction, contractional strain of � 0.007% to � 0.13% is indicated by the structures, corresponding to decreases in planetary radius of 112 m to 2.24 km, respectively. By contrast, consideration of all recognized thrust faults regardless of age produces a globally averaged contractional strain of � 0.011% to � 0.22%, corresponding to a radius decrease of 188 m to 3.77 km since the Early Noachian.

Previous theoretical work has suggested that porous sedimentary rocks subjected to sufficiently high strain rates may not form deformation band damage zones (DBDZs). This hypothesis is evaluated by an examination of faults within the porous Navajo Sandstone at the Upheaval Dome impact structure in Canyonlands National Park, southeastern Utah, where high strain-rate conditions are known to have occurred. We found no evidence for DBDZ formation along the accessible fault planes at Upheaval Dome. Instead, a layer of pulverized quartz grains within the Navajo Sandstone occurs adjacent to the fault planes. Similar material has been observed in association with dynamic rupture in crystalline and sedimentary rocks along the San Andreas fault in southern California and in metamorphic rocks along the Bosman fault in South Africa. Measured grain sizes obtained from the pulverized material collected at Upheaval Dome are consistent with strain rates of ∼1–3 × 10 3 s −1 . Pulverized sedimentary rocks along the San Andreas fault imply strain rates of ∼10 −2 to 10 1 s −1 . Strain rates along the faults at Upheaval Dome are well above the average values associated with intraplate tectonics but are consistent with, or faster than, seismic slip rates along faults such as the San Andreas fault. Our results support the hypothesized rate dependence of deformation in porous rocks.

The epigenetic mechanisms involved in establishing and maintaining genomic imprinting are steadily being unmasked. The nucleosome remodeling and histone deacetylation (NuRD) complex is implicated in regulating DNA methylation and expression of the maternally expressed H19 gene in preimplantation mouse embryos. To dissect further the function of the NuRD complex in genomic imprinting, we employed an RNA interference (RNAi) strategy to deplete the NuRD complex component Metastasis Tumor Antigen 2 (MTA2). We found that Mta2 is the only zygotically expressed Mta gene prior to the blastocyst stage, and that RNAi-mediated knockdown of Mta2 transcript leads to biallelic H19 expression and loss of DNA methylation in the differentially methylated region in blastocysts. In addition, biallelic expression of the paternally expressed Peg3 gene, but not Snrpn, is also observed in blastocysts following Mta2 knockdown. Loss of MTA2 protein does not result in a decrease in abundance of other NuRD components, including methyl-binding-CpG-binding domain protein 3 (MBD3), histone deacetylases 1 and 2 (HDACs 1 and 2), and chromodomain helicase DNA-binding protein 4 (CHD4). Taken together, our results support a role for MTA2 within the NuRD complex in genomic imprinting.

The Idaho National Laboratory (INL), under the auspices of the U.S. Department of Energy, is conducting research on the Very High Temperature Reactor (VHTR) design concept for the Next Generation Nuclear Plant (NGNP) Project. The reactor design will be a graphite moderated, thermal neutron spectrum reactor that will produce electricity and hydrogen in a highly efficient manner. The NGNP reactor core will be either a prismatic graphite block type core or a pebble bed core. The NGNP will use very high-burnup, low-enriched uranium, TRISO-coated fuel, and have a projected plant design service life of 60 years. The VHTR concept is considered to be the nearest-term reactor design that has the capability to efficiently produce hydrogen. The plant size, reactor thermal power, and core configuration will ensure passive decay heat removal without fuel damage or radioactive material releases during reactor core-accidents. The objectives of the NGNP Project are to: Demonstrate a full-scale prototype VHTR that is commercially licensed by the U.S. Nuclear Regulatory Commission, and Demonstrate safe and economical nuclear-assisted production of hydrogen and electricity. The DOE laboratories, led by the INL, perform research and development (R&D) that will be critical to the success of the NGNP, primarily in the areas of: high temperature gas reactor fuels behaviour, high temperature materials qualification, design methods development and validation, hydrogen production technologies energy conversion. This paper presents current R&D work that addresses fundamental thermal hydraulics issues that are relevant to a variety of possible NGNP designs.

Deformation-band networks at Buckskin Gulch, Utah, and the Big Hole fault, Utah, both formed in the Navajo Sandstone with similar initial porosity and permeability, at similar burial depths, and result in similar reductions in effective permeability. However, the band networks at Buckskin Gulch, which formed in a contractional tectonic setting, appear to be much more areally extensive and are not associated with any discrete faults having displacements greater than at most a few meters and more likely only a few tens of centimeters. In contrast, the bands at Big Hole fault are generally limited to the damage zone of a about 25-m (82-ft) displacement normal fault formed in a locally extensional environment. These results suggest that deformation bands in well core from extensional settings may be indicative of discrete damage zones associated with normal faults, whereas deformation bands in well core from contractional settings may be indicative of much more areally extensive deformation-band networks. The band networks in both cases will affect similar reductions in reservoir effective permeability, but only in the latter case will the affected area be sufficiently large to affect well performance.

International audience; The amount of contractional strain accommodated by a set of stylolites is analyzed by comparing the amplitudes of stylolitic teeth and spikes to independent measures of thinning of the enclosing layer. The scaling relations between along-strike trace length ( L) and the maximum ( Dmax) and average ( Davg) amplitudes of stylolitic topography are also investigated. The studied stylolites occur in a 212-mm thick limestone layer dragged into the damage zone of the Gubbio normal fault zone in central Italy. Layer thinning was assessed independently from the layer geometry, with a maximum value of ∼23% nearest the fault. A total of 28 mm of thinning are related to 24 stylolites whose lengths range from 6.4 to 146 mm with average amplitudes from 0.1 to 1.3 mm. The average and maximum amplitudes of stylolitic topography increase with stylolite length, with Davg = 0.0011 L0.17, r2 = 0.57, implying propagation to greater lengths as contractional strains increase along them. The stylolites increase in number and amplitude into the most thinned area, correlating with increasing contractional strain accommodated by the layer. The average amplitude of stylolites visible in outcrop provides a measure of the minimum magnitude of contractional strain in the rock, although other mechanisms such as grain-scale dissolution appear necessary to account for the remaining layer thinning.

The core bypass flow in a prismatic very high temperature reactor (VHTR) is an important design consideration and can have considerable impact on the condition of reactor core internals including fuels. The interstitial gaps are an inherent presence in the reactor core because of tolerances in manufacturing the blocks and the inexact nature of their installation. Furthermore, the geometry of the graphite blocks changes over the lifetime of the reactor because of thermal expansion and irradiation damage. The occurrence of hot spots in the core and lower plenum and hot streaking in the lower plenum (regions of very hot gas flow) are affected by bypass flow. In the present study, three-dimensional computational fluid dynamic (CFD) calculations of a typical prismatic VHTR are conducted to better understand bypass flow phenomena and establish an evaluation method for the reactor core using the commercial CFD code FLUENT. Parametric calculations changing several factors in a one-twelfth sector of a fuel column are performed. The simulations show the impact of each factor on bypass flow and the resulting flow and temperature distributions in the prismatic core. Factors include inter-column gap-width, turbulence model, axial heat generation profile and geometry change from irradiation-induced shrinkage in the graphite block region. It is shown that bypass flow provides a significant cooling effect on the prismatic block and that the maximum fuel and coolant channel outlet temperatures increase with an increase in gap-width, especially when a peak radial factor is applied to the total heat generation rate. Also, the presence of bypass flow causes a large lateral temperature gradient in the block and also dramatically increases the variation in coolant channel outlet temperatures for a given block that may have repercussions on the structural integrity of the graphite, the neutronics and the potential for hot streaking and hot spots occurring in the lower plenum.

The origin of Pantheon Fossae, a complex structure consisting of radial graben in the center of the Caloris basin, Mercury, has been debated since the structure was first imaged by the MESSENGER spacecraft. Three different formation hypotheses have been suggested, i.e. an origin associated with the Apollodorus impact into a previously domed Caloris basin floor, graben formation as surface expressions of dike intrusions and basin-interior uplift alone. In order to test the scenarios, detailed observations from the currently available imagery were compared to the proposed formation mechanisms. We evaluate these origin hypotheses by means of detailed interpretations of the graben characteristics and patterns, by comparing to radial structures from Earth and Venus, and by mechanical analyses for each formation hypothesis. Results indicate that the formation of Pantheon Fossae as the result of doming in the central part of the Caloris basin is more likely than it having formed in association with a radially symmetric stress field centered at or near the Apollodorus crater, that would have been created by a magma chamber or been superimposed on a pre-existing dome due to impact mechanics.

Removal of poly(A) tail is an important mechanism controlling eukaryotic mRNA turnover. The major eukaryotic deadenylase complex CCR4-NOT contains two deadenylase components, CCR4 and CAF1, for which mammalian CCR4 is encoded by Cnot6 or Cnot6l paralogs. We show that Cnot6l apparently supplies the majority of CCR4 in the maternal CCR4-NOT in mouse, hamster, and bovine oocytes. Deletion of Cnot6l yielded viable mice, but Cnot6l−/− females exhibited ∼40% smaller litter size. The main onset of the phenotype was post-zygotic: fertilized Cnot6l−/− eggs developed slower and arrested more frequently than Cnot6l+/− eggs, suggesting that maternal CNOT6L is necessary for accurate oocyte-to-embryo transition. Transcriptome analysis revealed major transcriptome changes in Cnot6l−/− ovulated eggs and one-cell zygotes. In contrast, minimal transcriptome changes in preovulatory Cnot6l−/− oocytes were consistent with reported Cnot6l mRNA dormancy. A minimal overlap between transcripts sensitive to decapping inhibition and Cnot6l loss suggests that decapping and CNOT6L-mediated deadenylation selectively target distinct subsets of mRNAs during oocyte-to-embryo transition in mouse.

In mammalian somatic cells, several pathways that converge on deadenylation, decapping, and 5'-3' degradation are found in cytoplasmic foci known as P-bodies. Because controlled mRNA stability is essential for oocyte-to-zygote transition, we examined the dynamics of P-body components in mouse oocytes. We report that oocyte growth is accompanied by loss of P-bodies and a subcortical accumulation of several RNA-binding proteins, including DDX6, CPEB, YBX2 (MSY2), and the exon junction complex. These proteins form transient RNA-containing aggregates in fully grown oocytes with a surrounded nucleolus chromatin configuration. These aggregates disperse during oocyte maturation, consistent with recruitment of maternal mRNAs that occurs during this time. In contrast, levels of DCP1A are low during oocyte growth, and DCP1A does not colocalize with DDX6 in the subcortical aggregates. The amount of DCP1A markedly increases during meiosis, which correlates with the first wave of destabilization of maternal mRNAs. We propose that the cortex of growing oocytes serves as an mRNA storage compartment, which contains a novel type of RNA granule related to P-bodies.

Segmented graben systems develop stepovers that have important implications in the exploration of oil and gas in extensional tectonic basins. We have compared and modeled a representative stepover between grabens in Canyonlands, Utah, and the North Sea Viking Graben and, despite their different structural settings, found striking similarities that pertain to other graben systems. In both cases, the stepovers represent relatively high parts within the graben systems that are likely to be among the first to be filled with hydrocarbons generated in deeper parts of the grabens. Furthermore, the relay ramps and smaller fault offsets in stepovers ease hydrocarbon migration and allow stepovers to act as preferred migration routes from deep graben kitchens to structurally higher traps in the basin. Graben stepovers and their related structures should be paid special attention during exploration because they may represent hydrocarbon accumulations complementary to larger traps along the graben flanks. These observations explain the location of the Kvitebjorn, Valemon, and Huldra fields in a stepover structure of the Viking Graben and encourage increased focus on similar graben stepovers in the Viking Graben and other graben systems.

Knight, Kris W., Richard C. Schultz, Cathy M. Mabry, and Thomas M. Isenhart, 2010. Ability of Remnant Riparian Forests, With and Without Grass Filters, to Buffer Concentrated Surface Runoff. Journal of the American Water Resources Association (JAWRA) 46(2):311-322. DOI: 10.1111/j.1752-1688.2010.00422.x Abstract: Riparian forest buffers established according to accepted conservation practice standards have been recommended as one of the most effective tools for mitigating nonpoint source pollution. The midwestern United States is characterized by many kilometers of narrow, naturally occurring forests along streams. However, little is known about the relative effectiveness of these remnant forests compared with these newly established buffers. This study compared the ability of naturally occurring remnant forests with and without adjacent planted grass filters to buffer concentrated flow paths (CFPs) originating in crop fields along first- and second-order streams in three northeast Missouri watersheds. Remnant forests breached by runoff through CFPs were narrower than those that dispersed 100% of the CFPs. Remnant forests with adjacent grass buffers were nearly twice the width as those without grass filters. We also found that CFPs, which developed within remnant forests and at the base of in-field grass waterways, were potential sources of sediments to streams. Methods to mitigate these CFPs warrant further investigation. Our study suggests that although these natural remnant forests provide substantial buffering capacity, both improved management and/or the addition of an adjacent grass filter would improve water quality by reducing sediment loss to streams. Inferences can be used to inform the design and management of similar conservation buffer systems within the region.

Previous studies have computed and modeled fluid flow through fractured rock with the parallel plate approach where the volumetric flow per unit width normal to the direction of flow is proportional to the cubed aperture between the plates, referred to as the traditional cubic law. When combined with the square root relationship of displacement to length scaling of opening-mode fractures, total flow rates through natural opening-mode fractures are found to be proportional to apertures to the fifth power. This new relationship was explored by examining a suite of flow simulations through fracture networks using the discrete fracture network model (DFN). Flow was modeled through fracture networks with the same spatial distribution of fractures for both correlated and uncorrelated fracture length-to-aperture relationships. Results indicate that flow rates are significantly higher for correlated DFNs. Furthermore, the length-to-aperture relations lead to power-law distributions of network hydraulic conductivity which greatly influence equivalent permeability tensor values. These results confirm the importance of the correlated square root relationship of displacement to length scaling for total flow through natural opening-mode fractures and, hence, emphasize the role of these correlations for flow modeling.

In response to concern about the loss of ecosystem services once provided by natural riparian systems, state and federal agencies have established incentive programs for landowners to convert sensitive lands from agricultural to conservation uses. Enhancement of wildlife habitat, while identified as a function of such systems, has often been of secondary importance to soil conservation and water quality objectives. Though greatly important, little consideration has been given to how specific species will respond to the design and management of riparian buffers or other conservation lands. This study compared avian communities within a chronosequence of riparian buffers established on previously cropped or pastured land with those of the nearby matrix land cover types (row crop fields and an intensively grazed pasture). The riparian buffers consisted of native grasses, forbs, and woody vegetation established at three different times (2, 9, and 14+ years prior to survey). At each site, 10 min point counts for breeding birds were conducted using 50 m fixed radius plots, which were visited eight times between May 15 and July 10, 2008. A total of 54 bird species were observed over all of the study sites. The re-established riparian buffers in this study had higher bird abundance, richness, and diversity than the crop and pasture sites. These results suggest that re-establishing native riparian vegetation in areas of intensive agriculture will provide habitat for a broad suite of bird species, but that specific species will reflect successional stage, horizontal and vertical vegetative structure, and compositional diversity of the buffer vegetation. These results emphasize the importance of matching buffer design and management to species requirements if the objectives are to attract specific target species or species groups.

Livestock grazing in the Midwestern United States can result in significant levels of runoff sediment and nutrient losses to surface water resources. Some of these contaminants can increase stream eutrophication and are suspected of contributing to hypoxic conditions in the Gulf of Mexico. This research quantified effects of livestock grazing management practices and vegetative filter strip buffers on runoff depth and mass losses of total solids, nitrate-nitrogen (NO3-N), and ortho-phosphorus (PO4-P) under natural hydrologic conditions. Runoff data were collected from 12 rainfall events during 2001 to 2003 at an Iowa State University research farm in central Iowa, United States. Three vegetative buffers (paddock area:vegetative buffer area ratios of 1:0.2, 1:0.1, and 1:0 no buffer [control]) and three grazing management practices (continuous, rotational, and no grazing [control]) comprised nine treatment combinations (vegetative buffer ratio/grazing management practice) replicated in three 1.35 ha (3.34 ac) plot areas. The total 4.05 ha (10.02 ac) study area also included nine 0.4 ha (1.0 ac) paddocks and 27 vegetative buffer runoff collection units distributed in a randomized complete block design. The study site was established on uneven terrain with a maximum of 15% slopes and consisted of approximately 100% cool-season smooth bromegrass. Average paddock and vegetative buffer plant tiller densities estimated during the 2003 project season were approximately 62 million and 93 million tillers ha−1 (153 million and 230 million tillers ac−1), respectively. Runoff sample collection pipe leakage discovered and corrected during 2001 possibly reduced runoff depth and affected runoff contaminant mass losses data values. Consequently, 2001 runoff analysis results were limited to treatment comparisons within the 2001 season and were not compared with 2002 and 2003 data. Analysis results from 2001 showed no significant differences in average losses of runoff, total solids, NO3-N, and PO4-P among the nine vegetative buffer/grazing practice treatment combinations. Results from 2002 indicated significantly higher losses of runoff and total solids from 1:0 no buffer/rotational grazing and 1:0 no buffer/continuous grazing treatment combination plots, respectively, compared among other 2002 season treatment combinations. The 2003 results showed significantly higher runoff and total solids losses from 1:0 no buffer/no grazing treatment combination plots compared among all 2003 treatment combinations and from 1:0.1 vegetative buffer/no grazing treatment combination plots compared among all 2003 treatment combinations and with respective 2002 treatment combinations. However, the 2003 results indicated effective vegetative buffer performance with significantly lower runoff, total solids, and NO3-N losses from the larger 1:0.2 buffer area compared among the smaller 1:0.1 buffer area and 1:0 no buffer treatment combinations. The 2003 results also indicated a highly significant increase in losses of NO3-N from 1:0.1 buffer/no grazing treatment combination plots compared among other 2003 season treatment combinations and with respective 2002 treatment combinations. Overall results from this study suggest a shift from significantly higher 2002 season plot losses of continuous and rotational grazing treatment combinations to significantly higher 2003 season losses of no grazing treatment combinations. We speculate this shift to significantly higher runoff and contaminant losses from no grazing treatment combination plots during 2003 reflects the variability inherent to a complex and dynamic soil-water environment of livestock grazing areas. However, we also hypothesize the environmental conditions that largely consisted of a dense perennial cool-season grass type, high-relief landscape, and relatively high total rainfall depth may not necessarily include livestock grazing activities.

As developed by M. Bakhtin, J. Kristeva, R. Barthes, and T. K. Beal, intertextual approaches have largely replaced the examination of inner-biblical quotation or allusion and literary influence studies in analyzing the relationships between texts and contexts. These studies, however, can involve the endless tracing of intertextual relations, undermining the possibility of determinate meaning. By deriving several key interpretive emphases and procedures from the intertextual theory of Michael Riffaterre, a Columbia University professor of French Literature, one can "redeem" intertextuality. This kind of modified approach to intertextuality, which is better suited to canonical Scripture, is illustrated by a detailed analysis of Isa 65:17–25. Reading Isa 65 in light of its primary intertexts results in a richer reading that directs the interpreter's attention to neglected textual features as well as latent emphases and associations.

Fertilization triggers a rise in intracellular Ca 2+ concentration ([Ca 2+ ] i ) in the egg that initiates a series of events known as egg activation. These events include cortical granule exocytosis that establishes a block to polyspermy, resumption of meiosis, and recruitment of maternal mRNAs into polysomes for translation. Several calcium-dependent proteins, including calcium/calmodulin-dependent protein kinase II (CaMKII), have been implicated in egg activation. However, the precise role of CaMKII in mediating specific events of egg activation and the identity of the isoform(s) present in mouse eggs have not been unequivocally established. Through targeted deletion of the γ isoform of CaMKII, we find that CaMKIIγ is the predominant CaMKII isoform in mouse eggs and that it is essential for egg activation. Although CaMKIIγ −/− eggs exhibit a normal pattern of Ca 2+ oscillations after insemination and undergo cortical granule exocytosis, they fail to resume meiosis or to recruit maternal mRNAs. Surprisingly, we find that the recruitment of maternal mRNAs does not directly depend on CaMKII, but requires elevated [Ca 2+ ] i and metaphase II exit. We conclude that CaMKIIγ specifically controls mouse egg activation by regulating cell cycle resumption.

Following fertilization the transition from a highly differentiated oocyte to a totipotent 2-cell embryo requires two unique mitotic cell cycles. The first cell cycle is characterized by a prolonged G(1) phase, DNA replication (S phase) that occurs separately in the female and male pronuclei, and a short G(2) phase that occur in the absence of cell growth. During the second cell cycle, G(1) is short whereas G(2) is prolonged and occurs concurrently with zygotic genome activation, which is essential for progression past the 2-cell stage. CDC14B, a dual specificity phosphatase that counteracts cyclin dependent kinase 1 (CDK1/CDC2A) action, regulates mitosis in somatic cells and prevents premature meiotic resumption in mouse oocytes. It is not known if CDC14B plays a role during the unique mitotic cell cycles of preimplantation development. We report that CDC14B is present in mouse embryos and localizes to mitotic centrosomes and spindles. Overexpressing CDC14B in 1-cell embryos results in 40% and 60% of the embryos arresting at the 1- and 2-cell stages, respectively. Embryos arrested at the 1-cell stage contained reduced CDC2A activity, whereas embryos arrested at the 2-cell stage were in G(2) and failed to activate the zygotic genome. In contrast, overexpressing CDC14B in meiotically-incompetent oocytes, which are arrested in a G(2)-like state and are transcriptionally active, does not repress global transcription. These data suggest that CDC14B is a negative regulator of the 1-to-2-cell transition and of zygotic genome activation in mouse embryogenesis.

Advanced maternal age is unequivocally associated with increased aneuploidy in human eggs and infertility, but the molecular basis for this phenomenon is unknown. An age-dependent deterioration of the spindle assembly checkpoint (SAC) has been proposed as a probable cause of aneuploidy. Accurate chromosome segregation depends on correct chromosome attachment to spindle microtubules, and the SAC provides time for this process by delaying anaphase onset until all chromosomes are stably attached. If SAC function decreases with age, oocytes from reproductively old mice would enter anaphase of meiosis I (AI) prematurely, leading to chromosome segregation errors and aneuploid eggs. Although intuitively appealing, this hypothesis is largely untested. We used a natural reproductive aging mouse model to determine if a defective SAC is the primary cause of aneuploidy in eggs. We tracked the progress of individual oocytes from young and old mice through meiosis I by time-lapse microscopy and counted chromosomes in the resulting eggs. This data set allowed us to correlate the timing of AI onset with aneuploidy in individual oocytes. We found that oocytes from old mice do not enter AI prematurely compared to young counterparts despite a 4-fold increase in the incidence of aneuploidy. Moreover, we did not observe a correlation between the timing of AI onset and aneuploidy in individual oocytes. When SAC function was challenged with a low concentration of the spindle toxin nocodazole, oocytes from both young and old mice arrested at meiosis I, which is indicative of a functional checkpoint. These findings indicate that a defective SAC is unlikely the primary cause of aneuploidy associated with maternal age.

The elevated incidence of aneuploidy in human oocytes warrants study of the molecular mechanisms regulating proper chromosome segregation. The Aurora kinases are a well-conserved family of serine/threonine kinases that are involved in proper chromosome segregation during mitosis and meiosis. Here we report the expression and localization of all three Aurora kinase homologs, AURKA, AURKB, and AURKC, during meiotic maturation of mouse oocytes. AURKA, the most abundantly expressed homolog, localizes to the spindle poles during meiosis I (MI) and meiosis II (MII), whereas AURKB is concentrated at kinetochores, specifically at metaphase of MI (Met I). The germ cell-specific homolog, AURKC, is found along the entire length of chromosomes during both meiotic divisions. Maturing oocytes in the presence of the small molecule pan-Aurora kinase inhibitor, ZM447439 results in defects in meiotic progression and chromosome alignment at both Met I and Met II. Over-expression of AURKB, but not AURKA or AURKC, rescues the chromosome alignment defect suggesting that AURKB is the primary Aurora kinase responsible for regulating chromosome dynamics during meiosis in mouse oocytes.

Subsurface lithology plays an important role in many riparian zone processes, but few studies have examined how sediment nutrient concentrations vary with depth. In this study, we evaluated concentrations of nutrients (N, C and P) with depth in a riparian zone of the glaciated Midwest. A total of 146 sediment samples were collected from 24 cores that extended to a maximum depth of 3.6 m at eight sites in the riparian zone of Walnut Creek. Subsurface deposits were predominantly silt loam, becoming coarser and more variable with depth. Nitrogen and carbon content ranged from

The final steps of oogenesis occur during oocyte maturation that generates fertilization-competent haploid eggs capable of supporting embryonic development. Cyclin-dependent kinase 1 (CDK1) drives oocyte maturation and its activity and actions on substrates are tightly regulated. CDC14 is a dual-specificity phosphatase that reduces CDK1 activity and reverses the actions of CDK1 during mitosis. In budding yeast, Cdc14 is essential for meiosis, but it is not known whether its mammalian homolog CDC14A is required for meiosis in females. Here, we report that CDC14A is concentrated in the nucleus of meiotically incompetent mouse oocytes but is dispersed throughout meiotically competent oocytes. During meiotic progression CDC14A has no specific sub-cellular localization except between metaphase of meiosis I (Met I) and metaphase of meiosis II (Met II) when it co-localizes with the central portion of the meiotic spindle. Overexpression of CDC14A generally delays meiotic progression after resumption of meiosis whereas microinjection of oocytes with an antibody against CDC14A specifically delays exit from Met I. Each of these perturbations generates eggs with chromosome alignment abnormalities and eggs that were injected with the CDC14A antibody had an elevated incidence of aneuploidy. Collectively, these data suggest that CDC14A regulates oocyte maturation and functions to promote the meiosis I-to-meiosis II transition as its homolog does in budding yeast.

Meiotic maturation in oocytes is a prolonged process that is unique because of cell cycle arrests at prophase of meiosis I (MI) and at metaphase of meiosis II (MII). Fluctuations in cyclin-dependent kinase 1 (CDK1/CDC2A) activity govern meiotic progression, yet little is known about how these fluctuations are achieved. CDC14 is a highly conserved dual-specificity phosphatase that counteracts the function of proteins phosphorylated by CDK. Mammals contain two CDC14 homologs, CDC14A and CDC14B. We report that CDC14B localizes with the meiotic spindle in mouse oocytes, and (unlike somatic cells) it does not localize in the nucleolus. Oocytes that overexpress CDC14B are significantly delayed in resuming meiosis and fail to progress to MII, whereas oocytes depleted of CDC14B spontaneously resume meiosis under conditions that normally inhibit meiotic resumption. Depletion of FZR1 (CDH1), a regulatory subunit of the anaphase-promoting complex/cyclosome that targets cyclin B1 (CCNB1) for ubiquitin-mediated proteolysis, partially restores normal timing of meiotic resumption in oocytes with excess CDC14B. These studies also reveal that experimentally altering CDC14B levels generates eggs with abnormal spindles and with chromosome alignment perturbations. Our data indicate that CDC14B is a negative regulator of meiotic resumption and may regulate MI in mouse oocytes.

High-resolution imagery reveals unprecedented lines of evidence for the presence of deformation band clusters in layered sedimentary deposits in the equatorial region of Mars. Deformation bands are a class of geologic structural discontinuity that is a precursor to faults in clastic rocks and soils. Clusters of deformation bands, consisting of many hundreds of individual subparallel bands, can act as important structural controls on subsurface fl uid fl ow in terrestrial reservoirs, and evidence of diagenetic processes is often preserved along them. Deformation band clusters are identifi ed on Mars based on characteristic meter-scale architectures and geologic context as observed in data from the High-Resolution Imaging Science Experiment (HiRISE) camera. The identifi cation of deformation band clusters on Mars is a key to investigating the migration of fl uids between surface and subsurface reservoirs in the planet’s vast sedimentary deposits. Similar to terrestrial examples, evidence of diagenesis in the form of lightand dark-toned discoloration and wall-rock induration is recorded along many of the deformation band clusters on Mars. Therefore, these structures are important sites for future exploration and investigations into the geologic history of water and waterrelated processes on Mars.

A nonapeptide Ac-His-Phe-Gly-Cys-D-Phe-Ser-Gly-Glu-Cys-NH2 (XI) cyclized through the cysteines at positions 4 and 9 is synthesized as a model active site for the enzyme alpha-chymotrypsin. A CPK model of XI indicates that the peptide will have a high probability of folding into a conformation in which the two beta-phenyls interact to form a hydrophobic site to one side of the cyclohexyl structure, and the Ser-His-Glu side chains form a hydrogen bonded triad over the plane of cyclopeptidyl structure. Substrates can then bind at the hydrophobic pocket formed by the beta-phenyls and be acted upon by the Ser-His-Glu catalytic triad, as in the enzyme. 1H. n.m.r. shows: (i) multiplet peaks for the phenyl protons in D2O that condense to a singlet in DMSO-d6, (ii) a perturbation of the phenyl protons chemical shift on proflavin association to XI, and (iii) perturbation of the His pKa to a higher value on association of proflavin to XI. These data support the existence of a hydrophobic site and a Glu-His interaction in the peptide. Furthermore, the greater than 10(2) better affinity of proflavin to XI than to AcTrp supports the existence of a hydrophobic site. However, no acceleration of p-nitrophenyl acetate or trans-cinnamoyl imidazole hydrolysis over that of imidazole is observed. The possible reasons for a lack of esterase activity in XI and other peptidyl models of serine protease active sites are discussed.

Sumoylation is a posttranslational modification in which SUMO (small ubiquitin-related modifier) proteins are covalently attached to their substrates. In vertebrates, developmental roles for sumoylation have been studied, but the function of sumoylation during mammalian oocyte growth and maturation is not known. As a prelude to conducting studies on the role of sumoylation during oocyte development, we analyzed the temporal and spatial pattern of expression of UBE2I, a SUMO-conjugating E2 enzyme. Immunocytochemical analysis of UBE2I revealed a punctate nuclear staining pattern, with transcriptionally quiescent, fully grown, GV-intact oocytes having larger UBE2I-containing bodies than transcriptionally active, meiotically incompetent growing oocytes. Inhibiting transcription in incompetent oocytes resulted in an increase in the size of the UBE2I-containing bodies. Overexpression of either wild-type UBE2I or catalytically inactive UBE2I resulted in an increase in the size of the UBE2I-containing bodies but also an increase in BrUTP incorporation, suggesting that transcriptional activation by UBE2I is independent of its catalytic activity. Although UBE2I-containing bodies did not completely colocalize with SUMO1 or SUMO2 and SUMO3, which were localized mainly on the nuclear membrane and in the nucleoplasm, UBE2I strikingly colocalized with SFRS2, which is a component of nuclear speckles and critical for mRNA processing. These results suggest a novel function for UBE2I and therefore sumoylation in gene expression..

CTCF is a multifunctional nuclear factor involved in epigenetic regulation. Despite recent advances that include the systematic discovery of CTCF-binding sites throughout the mammalian genome, the in vivo roles of CTCF in adult tissues and during embryonic development are largely unknown. Using transgenic RNAi, we depleted maternal stores of CTCF from growing mouse oocytes, and identified hundreds of misregulated genes. Moreover, our analysis suggests that CTCF predominantly activates or derepresses transcription in oocytes. CTCF depletion causes meiotic defects in the egg, and mitotic defects in the embryo that are accompanied by defects in zygotic gene expression, and culminate in apoptosis. Maternal pronuclear transfer and CTCF mRNA microinjection experiments indicate that CTCF is a mammalian maternal effect gene, and that persistent transcriptional defects rather than persistent chromosomal defects perturb early embryonic development. This is the first study detailing a global and essential role for CTCF in mouse oocytes and preimplantation embryos.

Aurora kinase A (AURKA), which is a centrosome-localized serine/threonine kinase crucial for cell cycle control, is critically involved in centrosome maturation and spindle assembly in somatic cells. Active T288 phosphorylated AURKA localizes to the centrosome in the late G(2) and also spreads to the minus ends of mitotic spindle microtubules. AURKA activates centrosomal CDC25B and recruits cyclin B1 to centrosomes. We report here functions for AURKA in meiotic maturation of mouse oocytes, which is a model system to study the G(2) to M transition. Whereas AURKA is present throughout the entire GV-stage oocyte with a clear accumulation on microtubule organizing centers (MTOC), active AURKA becomes entirely localized to MTOCs shortly before germinal vesicle breakdown. In contrast to somatic cells in which active AURKA is present at the centrosomes and minus ends of microtubules, active AURKA is mainly located on MTOCs at metaphase I (MI) in oocytes. Inhibitor studies using Roscovitine (CDK1 inhibitor), LY-294002 (PI3K inhibitor) and SH-6 (PKB inhibitor) reveal that activation of AURKA localized on MTOCs is independent on PI3K-PKB and CDK1 signaling pathways and MOTC amplification is observed in roscovitine- and SH-6-treated oocytes that fail to undergo nuclear envelope breakdown. Moreover, microinjection of Aurka mRNA into GV-stage oocytes cultured in 3-isobutyl-1-methyl xanthine (IBMX)-containing medium to prevent maturation also results in MOTC amplification in the absence of CDK1 activation. Overexpression of AURKA also leads to formation of an abnormal MI spindle, whereas RNAi-mediated reduction of AURKA interferes with resumption of meiosis and spindle assembly. Results of these experiments indicate that AURKA is a critical MTOC-associated component involved in resumption of meiosis, MTOC multiplication, proper spindle formation and the metaphase I-metaphase II transition.

Reducing non-point source phosphorus (P) pollution is often necessary to improve water quality in agricultural streams. Soil total P (TP) concentrations and compaction are soil characteristics that can influence P losses to streams. The objective of this study was to compare these two soil characteristics among riparian forest buffers, grass filters, pastures with cattle fenced out of the stream, intensive rotational, rotational and continuously grazed pastures and row-cropped fields in three physiographic regions of Iowa. Soil TP and compaction for the seven riparian land-uses were determined in stream bank and surface riparian soils. Total P concentrations in stream bed material along the seven riparian land-uses were also measured. Total P concentrations in riparian stream bank soils among land-uses ranged from 303 to 398 mg kg−1 in the central region, to 432–518 mg kg−1 in the northeast, to 360–555 mg kg−1 in the southeast. In the surface riparian soils TP among land-uses ranged from 434 to 649 mg kg−1 in the central region, to 493–764 mg kg−1 in the northeast region, to 428–716 mg kg−1 in the southeast region. Finally, the TP concentrations in the stream bed sediments among land-uses ranged 194–307 mg kg−1 in the central region, to 169–461 mg kg−1 in the northeast, to 389–964 mg kg−1 in the southeast. Few soil TP significant differences among riparian land-uses within regions were found. Soil compaction under some of the grazing practices was significantly higher than under the conservation practices. Limited differences in soil TP concentrations and compaction were partially due to the young age of the conservation practices and the rotational and intensive rotational pastures. Past land-use on these sites had been either continuous grazing or row-cropping and those uses were still influencing these soil parameters. Within riparian land-uses, surface riparian soils generally had higher TP than the stream bank riparian soils. Stream bed samples had lower TP concentrations than the riparian soils in the northeast and central regions but were higher than the riparian soils in some of the land-uses in the southeast region. Overall TP concentrations in the stream bank, surface riparian soils and stream bed material were high indicating that these areas can potentially be important source areas of P and the focus should be on reducing the transport of P.

Phosphorus and sediment are major nonpoint source pollutants that degrade water quality. Streambank erosion can contribute a significant percentage of the phosphorus and sediment load in streams. Riparian land-uses can heavily influence streambank erosion. The objective of this study was to compare streambank erosion along reaches of row-cropped fields, continuous, rotational and intensive rotational grazed pastures, pastures where cattle were fenced out of the stream, grass filters and riparian forest buffers, in three physiographic regions of Iowa. Streambank erosion was measured by surveying the extent of severely eroding banks within each riparian land-use reach and randomly establishing pin plots on subsets of those eroding banks. Based on these measurements, streambank erosion rate, erosion activity, maximum pin plot erosion rate, percentage of streambank length with severely eroding banks, and soil and phosphorus losses per unit length of stream reach were compared among the riparian land-uses. Riparian forest buffers had the lowest streambank erosion rate (15-46 mm/year) and contributed the least soil (5-18 tonne/km/year) and phosphorus (2-6 kg/km/year) to stream channels. Riparian forest buffers were followed by grass filters (erosion rates 41-106 mm/year, soil losses 22-47 tonne/km/year, phosphorus losses 9-14 kg/km/year) and pastures where cattle were fenced out of the stream (erosion rates 22-58 mm/year, soil losses 6-61 tonne/km/year, phosphorus losses 3-34 kg/km/year). The streambank erosion rates for the continuous, rotational, and intensive rotational pastures were 101-171, 104-122, and 94-170 mm/year, respectively. The soil losses for the continuous, rotational, and intensive rotational pastures were 197-264, 94-266, and 124-153 tonne/km/year, respectively, while the phosphorus losses were 71-123, 37-122, and 66 kg/km/year, respectively. The only significant differences for these pasture practices were found among the percentage of severely eroding bank lengths with intensive rotational grazed pastures having the least compared to the continuous and rotational grazed pastures. Row-cropped fields had the highest streambank erosion rates (239 mm/year) and soil losses (304 tonne/km/year) and very high phosphorus losses (108 kg/km/year).

Superimposed on activation of the embryonic genome in preimplantation mouse embryos is the formation of a chromatin-mediated transcriptionally repressive state that arises in the late two-cell embryo and becomes more pronounced with development. In this study, we investigated expression and function of Class I histone deacetylases (HDAC) HDAC1, HDAC2, and HDAC3 during preimplantation development. HDAC1 is likely a major deacetylase in preimplantation embryos and its expression inversely correlates with changes in the acetylation state of histone H4K5 during preimplantation development. RNAi-mediated reduction of HDAC1 leads to hyperacetylation of histone H4 and a developmental delay even though expression of HDAC2 and HDAC3 is significantly induced in Hdac1-suppresssed embryos; increased expression of p21Cip1/Waf may contribute to the observed developmental delay. RNAi-mediated reduction of HDAC2 has no noticeable effect on preimplantation development, suggesting that individual HDACs have distinct functions during preimplantation development. Although RNAi-mediated targeting of Hdac3 mRNA was very efficient, maternal HDAC3 protein was stable during preimplantation development, thereby preventing an examination of its role. HDAC1 knockdown does not increase the rate of global transcription in late 2-cell embryos, but does result in elevated levels of expression of a subset of genes; this increased expression correlates with hyperacetylation of histone H4. Results of these experiments suggest that HDAC1 is involved in the development of a transcriptionally repressive state that initiates in 2-cell embryos.

Strain localization structures such as fractures, stylolites, and deformation bands have important effects on reservoir performance but lack a consistent terminology. Advances in the recognition and interpretation of such structures now motivate a comprehensive framework that stresses their similarities instead of their differences. We review and assess the classical terms for localized geologic structures, followed by a comprehensive nomenclature that accounts for joints, faults, fractures, anticracks, shear zones, and deformation bands in compact and high-porosity rocks. Geologic structural discontinuities are defined by their lengths and by the sense and rate of displacement change across them. For example, structural discontinuities having negligible thickness, and consequently, a discontinuous displacement across them, are called sharp discontinuities. Depending on the sense of displacement (opening, shearing, or closing), these structures are called cracks, faults, or anticracks. However, structural discontinuities having a measurable thickness in outcrop or hand specimen and a continuous change in displacement across them are called tabular discontinuities. Correspondingly, these types of deformation bands are called dilation bands, shear bands, or compaction bands. The class of structural discontinuity, i.e., sharp or tabular, depends on the properties of the deforming rock. Consistent characteristics and patterns of these structural discontinuities, and their displacement-length scaling relations, demonstrate the rich yet consistent varieties of strain localization that are manifested in crustal rocks in general, and reservoir rocks in particular.

Virtual Globe software has become extremely popular both inside and outside of educational settings. This software allows users to explore the Earth in three dimensions while streaming satellite imagery, elevation, and other data from the Internet. Virtual Globes, such as Google Earth, NASA World Wind, and ESRI's ArcGIS Explorer can be effectively used in standards-based, inquiry-driven geography lessons. With some practice, mashups (using data from more than one source to create new data) can be constructed for practically any application or area of interest. Educators who have not already begun to use these tools may wish to investigate them to help their students to think spatially by investigating processes and places on the Earth's surface in a three-dimensional visualization environment.

Over evolutionary time, many genes undergo duplication and one copy accumulates mutations that render it non-functional. These 'pseudogenes' are generally thought to be rather uninteresting, dead-end pieces of the genome. Yet there now appears to be more to it than that. Two groups report in this issue on pseudogenes that can in fact influence gene expression. The mechanism involves pairing of RNA antisense transcripts from pseudogenes with the mRNAs of protein-coding genes, forming a duplex RNA that is processed into endogenous siRNAs. Over evolutionary time genes can undergo duplication, and may accumulate mutations that render them non-functional pseudogenes, which are thought to be uninteresting. This study (and that of the group of Sasaki) shows that pseudogenes can in fact influence gene expression. Pseudogenes populate the mammalian genome as remnants of artefactual incorporation of coding messenger RNAs into transposon pathways1. Here we show that a subset of pseudogenes generates endogenous small interfering RNAs (endo-siRNAs) in mouse oocytes. These endo-siRNAs are often processed from double-stranded RNAs formed by hybridization of spliced transcripts from protein-coding genes to antisense transcripts from homologous pseudogenes. An inverted repeat pseudogene can also generate abundant small RNAs directly. A second class of endo-siRNAs may enforce repression of mobile genetic elements, acting together with Piwi-interacting RNAs. Loss of Dicer, a protein integral to small RNA production, increases expression of endo-siRNA targets, demonstrating their regulatory activity. Our findings indicate a function for pseudogenes in regulating gene expression by means of the RNA interference pathway and may, in part, explain the evolutionary pressure to conserve argonaute-mediated catalysis in mammals.

An increase in the incidence of aneuploidy is well documented with increasing maternal age, in particular in human females. Remarkably, little is known regarding the underlying molecular basis for the age-associated increase in aneuploidy, which is a major source of decreased fertility in humans. Using mouse as a model system we find that eggs obtained from old mice (60-70 weeks of age) display a 6-fold increase in the incidence of hyperploidy as assessed by chromosome spreads. Expression profiling of transcripts in oocytes and eggs obtained from young and old mice reveals that approximately 5% of the transcripts are differentially expressed in oocytes obtained from old females when compared to oocytes obtained from young females (6-12 weeks of age) and that this fraction increases to approximately 33% in eggs. The latter finding indicates that the normal pattern of degradation of maternal mRNAs that occurs during oocyte maturation is dramatically altered in eggs obtained from old mice and could therefore be a contributing source to the decline in fertility. Analysis of the differentially expressed transcripts also indicated that the strength of the spindle assembly checkpoint is weakened and that higher errors of microtubule-kinetochore interactions constitute part of molecular basis for the age-associated increase in aneuploidy in females. Last, BRCA1 expression is reduced in oocytes obtained from old females and RNAi-mediated reduction of BRCA1 in oocytes obtained from young females results in perturbing spindle formation and chromosome congression following maturation.

The very high temperature reactor (VHTR) system behavior should be predicted during normal operating conditions and postulated accident conditions. The plant accident scenario and the passive safety behavior should be accurately predicted. Uncertainties in passive safety behavior could have large effects on the resulting system characteristics. Due to these performance issues in the VHTR, there is a need for development, testing and validation of design tools to demonstrate the feasibility of the design concepts and guide the improvement of the plant components. One of the identified design issues for the gas-cooled reactor is the thermal mixing of the coolant exiting the core into the outlet plenum. Incomplete thermal mixing may give rise to thermal stresses in the downstream components. To provide flow details, the analysis presented in this paper was performed by coupling a VHTR model generated in a thermal hydraulic systems code to a computational fluid dynamics (CFD) outlet plenum model. The outlet conditions obtained from the systems code VHTR model provide the inlet boundary conditions to the CFD outlet plenum model. By coupling the two codes in this manner, the important three-dimensional flow effects in the outlet plenum are well modeled while avoiding modeling the entire reactor with a computationally expensive CFD code. The values of pressure, mass flow rate and temperature across the coupled boundary showed differences of less than 5% in every location except for one channel. The coupling auxiliary program used in this analysis can be applied to many different cases requiring detailed three-dimensional modeling in a small portion of the domain.

Because low levels of DNA double strand breaks (DSBs) appear not to activate the ATM-mediated prophase I checkpoint in full-grown oocytes, there may exist mechanisms to protect chromosome integrity during meiotic maturation. Using live imaging we demonstrate that low levels of DSBs induced by the radiomimetic drug Neocarzinostatin (NCS) increase the incidence of chromosome fragments and lagging chromosomes but do not lead to APC/C activation and anaphase onset delay. The number of DSBs, represented by γH2AX foci, significantly decreases between prophase I and metaphase II in both control and NCS-treated oocytes. Transient treatment with NCS increases >2-fold the number of DSBs in prophase I oocytes, but less than 30% of these oocytes enter anaphase with segregation errors. MRE11, but not ATM, is essential to detect DSBs in prophase I and is involved in H2AX phosphorylation during metaphase I. Inhibiting MRE11 by mirin during meiotic maturation results in anaphase bridges and also increases the number of γH2AX foci in metaphase II. Compromised DNA integrity in mirin-treated oocytes indicates a role for MRE11 in chromosome integrity during meiotic maturation.

Inositol 1,4,5-trisphosphate generated by the action of a phospholipase C (PLC) mediates release of intracellular Ca2+ that is essential for sperm-induced activation of mammalian eggs. Much attention currently focuses on the role of sperm-derived PLCzeta in generating changes in egg intracellular Ca2+ despite the fact that PLCzeta constitutes a very small fraction of the total amount of PLC in a fertilized egg. Eggs express several isoforms of PLC, but a role for an egg-derived PLC in sperm-induced Ca2+ oscillations has not been examined. Reducing egg PLCbeta1 by a transgenic RNAi approach resulted in a significant decrease in Ca2+ transient amplitude, but not duration or frequency, following insemination. Furthermore, overexpressing PLCbeta1 by microinjecting a Plcb1 cRNA significantly perturbed the duration and frequency of Ca2+ transients and disrupted the characteristic shape of the first transient. These results provide the first evidence for a role of an egg-derived PLC acting in conjunction with a sperm-derived PLCzeta in egg activation.

Time-resolved infrared absorption spectroscopy is used to investigate the kinetics of the linkage isomerization reaction M(CO)5(η1-L) → M(CO)5(η2-L), where M = Cr, Mo, or W, and L = 2-methyl-2,3-dihydrofuran or 2,3-dihydropyran. Photolysis of M(CO)6 in cyclohexane in the presence of excess L produces the η1 (O-bound) isomer as the sole kinetic product. The kinetic product subsequently reacts intramolecularly to form an equilibrium mixture of the η1 and η2 (CC bound) isomers. Activation and equilibrium parameters are derived for the reactions and compared with previous results for linkage isomerization of the M(CO)5(dihydrofuran) complexes. The results of the experimental study, supported by DFT calculations, indicate that for M = W the kinetics of the η1 → η2 isomerization depend primarily on how close the double bond is to the metal atom in the η1 isomer, while the thermodynamics of the η1 ⇄ η2 equilibrium are determined primarily by electronic factors. In contrast, for M = Cr and Mo, both steric and ele...

Deformation bands are the most common strain localization feature found in deformed porous sandstones and sediments, including Quaternary deposits, soft gravity slides and tectonically affected sandstones in hydrocarbon reservoirs and aquifers. They occur as various types of tabular deformation zones where grain reorganization occurs by grain sliding, rotation and/or fracture during overall dilation, shearing, and/or compaction. Deformation bands with a component of shear are most common and typically accommodate shear offsets of millimetres to centimetres. They can occur as single structures or cluster zones, and are the main deformation element of fault damage zones in porous rocks. Factors such as porosity, mineralogy, grain size and shape, lithification, state of stress and burial depth control the type of deformation band formed. Of the different types, phyllosilicate bands and most notably cataclastic deformation bands show the largest reduction in permeability, and thus have the greatest potential to influence fluid flow. Disaggregation bands, where non-cataclastic, granular flow is the dominant mechanism, show little influence on fluid flow unless assisted by chemical compaction or cementation.

Field and microstructural observations from Upheaval Dome, in Canyonlands National Park, Utah, show that inelastic strain of the Wingate Sandstone is localized along compactional deformation bands. These bands are tabular discontinuities (b0.5 cm thick) that accommodate inelastic shear and compaction of inter-granular volume. Measurements of porosity and grain size from nondeformed samples are used to define a set of capped strength envelopes for the Wingate Sandstone. These strength envelopes reveal that compactional deformation bands require at least ca. 0.7 GPa (and potentially more than 2.3 GPa) of effective mean stress in order to nucleate within this sandstone. We find that the most plausible geologic process capable of generating these required magnitudes of mean stress is a meteoritic impact. Therefore the compactional deformation bands observed within the Wingate Sandstone are additional evidence of an impact event at Upheaval Dome and support a post-Wingate (post-Early Jurassic) age for this impact. © 2007 Elsevier B.V. All rights reserved.

Cloned embryos produced by somatic cell nuclear transfer (SCNT) display a plethora of phenotypic characteristics that make them different from fertilized embryos, indicating defects in the process of nuclear reprogramming by the recipient ooplasm. To elucidate the extent and timing of nuclear reprogramming, we used microarrays to analyze the transcriptome of mouse SCNT embryos during the first two cell cycles. We identified a large number of genes mis-expressed in SCNT embryos. We found that genes involved in transcription and regulation of transcription are prominent among affected genes, and thus may be particularly difficult to reprogram, and these likely cause a ripple effect that alters the transcriptome of many other functions, including oxidative phosphorylation, transport across membrane, and mRNA transport and processing. Interestingly, we also uncovered widespread alterations in the maternal (i.e., non-transcribed) mRNA population of SCNT embryos. We conclude that gene expression in early SCNT embryos is grossly abnormal, and that this is at least in part the result of incomplete reprogramming of transcription factor genes.

Summary The molecular basis for asymmetric meiotic divisions in mammalian oocytes that give rise to mature eggs and polar bodies remains poorly understood. Previous studies demonstrated that the asymmetrically positioned meiotic chromosomes provide the cue for cortical polarity in mouse oocytes. Here we show that the chromatin-induced cortical response can be fully reconstituted by injecting DNA-coated beads into metaphase II-arrested eggs. The injected DNA beads induce a cortical actin cap, surrounded by a myosin II ring, in a manner that depends on the number of beads and their distance from the cortex. The Ran GTPase plays a critical role in this process, because dominant-negative and constitutively active Ran mutants disrupt DNA-induced cortical polarization. The Ran-mediated signaling to the cortex is independent of the spindle but requires cortical myosin II assembly. We hypothesize that a Ran GTP gradient serves as a molecular ruler to interpret the asymmetric position of the meiotic chromatin.

Rural communities of sub-Saharan Africa are under increasing adaptive pressure resulting from decline in the quality of land resources. To increase food, generate income, and safeguard against risks and shocks, families are engaging in multiple livelihood strategies. This study was conducted to: 1) evaluate livelihood strategies; 2) examine the dynamic diversification process in the agrarian and non-agrarian continuum; and 3) investigate how type and availability of assets influences choice of a livelihood strategy. Results from our investigation in western Kenya suggest that as land is subjected to degradation, there is a shift in the type of assets that families can draw upon. Among the Luo, collision between deeply embedded cultural beliefs and access to land, is leading to a shift from farming to non-farming activities. They are heavily reliant on human labor to make a living hence becoming less resilient, and more vulnerable to existing and emerging risks and shocks. The overriding scenario is escalated land degradation, increased poverty levels, and a failed social support system. Asset diversification and intensification processes among the Kipsigis are closely intertwined with rapid social-cultural change and strong bonding and bridging ties. They are involved in an asset-led intensification and diversification strategies. Overall, our findings suggest that the ability to make a meaningful livelihood is dependent not only on the quality and quantity of assets that an individual household possesses, but also having capabilities to use and transform the assets as well.