Dating of Multistage Fluid Flow in Sandstones Mark, Darren F.; Parnell, John; Kelley, Simon P. ...
Science (American Association for the Advancement of Science),
09/2005, Volume:
309, Issue:
5743
Journal Article
Peer reviewed
Through ultraviolet laser argon-argon dating of potassium feldspar cements containing fluid inclusions, we determined temperature-composition-time data for paleofluids in a sedimentary basin, ...including data for an evolving episode of fluid flow recorded in distinct phases of cement. The fluid evolved from mixed aqueous oil 83 million years ago to purely aqueous by 76 million years ago, thus dating the time of oil charge in this reservoir.
Obesity is a risk factor for colorectal cancer (CRC), and alterations in the colonic microbiome and metabolome may be mechanistically involved in this relationship. The relative contribution of diet ...and obesity per se are unclear. We compared the effect of diet- and genetically-induced obesity on the intestinal microbiome and metabolome in a mouse model of CRC. Apc.sup.1638N mice were made obese by either high fat (HF) feeding or the presence of the Lepr.sup.db/db (DbDb) mutation. Intestinal tumors were quantified and stool microbiome and metabolome were profiled. Genetic obesity, and to a lesser extent HF feeding, promoted intestinal tumorigenesis. Each induced distinct microbial patterns: taxa enriched in HF were mostly Firmicutes (6 of 8) while those enriched in DbDb were split between Firmicutes (7 of 12) and Proteobacteria (5 of 12). Parabecteroides distasonis was lower in tumor-bearing mice and its abundance was inversely associated with colonic Il1b production (p0.05). HF and genetic obesity altered the abundance of 49 and 40 fecal metabolites respectively, with 5 in common. Of these 5, adenosine was also lower in obese and in tumor-bearing mice (p0.05) and its concentration was inversely associated with colonic Il1b and Tnf production (p0.05). HF and genetic obesity differentially alter the intestinal microbiome and metabolome. A depletion of adenosine and P.distasonis in tumor-bearing mice could play a mechanistic role in tumor formation. Adenosine and P. distasonis have previously been shown to be anti-inflammatory in the colon and we postulate their reduction could promote tumorigenesis by de-repressing inflammation.
Intrinsic water use efficiency (iWUE), defined as the ratio of photosynthesis to stomatal conductance, is a key variable in plant physiology and ecology. Yet, how rising atmospheric CO
concentration ...affects iWUE at broad species and ecosystem scales is poorly understood. In a field-based study of 244 woody angiosperm species across eight biomes over the past 25 years of increasing atmospheric CO
(~45 ppm), we show that iWUE in evergreen species has increased more rapidly than in deciduous species. Specifically, the difference in iWUE gain between evergreen and deciduous taxa diverges along a mean annual temperature gradient from tropical to boreal forests and follows similar observed trends in leaf functional traits such as leaf mass per area. Synthesis of multiple lines of evidence supports our findings. This study provides timely insights into the impact of Anthropocene climate change on forest ecosystems and will aid the development of next-generation trait-based vegetation models.
3D Magnetic Reconnection Parnell, Clare E.; Maclean, Rhona C.; Haynes, Andrew L. ...
Proceedings of the International Astronomical Union,
06/2010, Volume:
6, Issue:
S271
Journal Article
Peer reviewed
Open access
Magnetic reconnection is an important process that is prevalent in a wide range of astrophysical bodies. It is the mechanism that permits magnetic fields to relax to a lower energy state through the ...global restructuring of the magnetic field and is thus associated with a range of dynamic phenomena such as solar flares and CMEs. The characteristics of three-dimensional reconnection are reviewed revealing how much more diverse it is than reconnection in two dimensions. For instance, three-dimensional reconnection can occur both in the vicinity of null points, as well as in the absence of them. It occurs continuously and continually throughout a diffusion volume, as opposed to at a single point, as it does in two dimensions. This means that in three-dimensions field lines do not reconnect in pairs of lines making the visualisation and interpretation of three-dimensional reconnection difficult. By considering particular numerical 3D magnetohydrodynamic models of reconnection, we consider how magnetic reconnection can lead to complex magnetic topologies and current sheet formation. Indeed, it has been found that even simple interactions, such as the emergence of a flux tube, can naturally give rise to ‘turbulent-like’ reconnection regions.
Heterochromatin, constitutively condensed chromosomal material, is widespread among eukaryotes but incompletely characterized at the nucleotide level. We have sequenced and analyzed 2.1 megabases ...(Mb) of
Arabidopsis thaliana chromosome 4 that includes 0.5–0.7 Mb of isolated heterochromatin that resembles the chromosomal knobs described by Barbara McClintock in maize. This isolated region has a low density of expressed genes, low levels of recombination and a low incidence of genetrap insertion. Satellite repeats were absent, but tandem arrays of long repeats and many transposons were found. Methylation of these sequences was dependent on chromatin remodeling. Clustered repeats were associated with condensed chromosomal domains elsewhere. The complete sequence of a heterochromatic island provides an opportunity to study sequence determinants of chromosome condensation.
Nous présentons les preuves archéologiques d’un établissement commercial datant du XIIIe au milieu du XVIe siècle EC sur un promontoire élevé du village de Lamreh, à environ 30 km à l’est de Banda ...Aceh, sur la côte nord de Sumatra, en Indonésie. Nous l’identifions au site historique de Lamri, décrit par les sources textuelles comme un noeud important de la « route de la soie » maritime entre le IXe et le XVIe siècle EC. Notre prospection a révélé de grandes concentrations de céramiques sur le promontoire, qui datent du début du XIIIe siècle jusqu’au milieu du XVIe siècle, certaines de qualité impériale. Plusieurs des stèles funéraires musulmanes de ce site sont d’un type particulier et datent de la quasi-totalité du XVe siècle. Les données géologiques suggèrent que les parties basses de Lamri ont été détruites par un fort tsunami à la fin du XIVe siècle. Cependant, nos données montrent que l’activité sur le promontoire s’est poursuivie jusqu’à ce que le site soit abandonné au milieu du XVIe siècle. L’absence de culture matérielle datant du IXe au XIIIe siècle suggère que les références textuelles antérieures à Lamri se référaient plus généralement à une grande partie de la côte nord de Sumatra, le village de Lamreh ne devenant le centre géographique du Lamri historique qu’après le tournant du XIIIe siècle.
We present archaeological evidence for a trading settlement dating from the 13th to the mid-16th century ce on an elevated headland in Lamreh village about 30 km east of Banda Aceh, on the northern coast of Sumatra, Indonesia. We propose this site was part of historic Lamri, known from documentary sources as an important node in the maritime “silk road” between the 9th to 16th centuries CE. Our landscape archaeological survey revealed large concentrations of ceramics on the headland that span from the early 13th through the mid-16th century, some of them of imperial quality. Several of the Muslim grave markers at this site are of a distinctive type and date across nearly the entire range of the 15th century. Geological evidence suggests low-lying parts of Lamri were destroyed by a major tsunami at the end of the 14th century. However, our data show that activity on the elevated headland continued until the site was abandoned in the mid-16th century. The lack of material culture dating from the 9th to 13th centuries suggests that earlier textual references to Lamri referred more generally to a broad stretch of the north Sumatran coast, with the headland in Lamreh village emerging as the geographic centre of historic Lamri after the turn of the 13th century.
Abstract The co-authors of this paper hereby state their intention to work together to launch the Genomic Observatories Network (GOs Network) for which this document will serve as its Founding ...Charter. We define a Genomic Observatory as an ecosystem and/or site subject to long-term scientific research, including (but not limited to) the sustained study of genomic biodiversity from single-celled microbes to multicellular organisms.An international group of 64 scientists first published the call for a global network of Genomic Observatories in January 2012. The vision for such a network was expanded in a subsequent paper and developed over a series of meetings in Bremen (Germany), Shenzhen (China), Moorea (French Polynesia), Oxford (UK), Pacific Grove (California, USA), Washington (DC, USA), and London (UK). While this community-building process continues, here we express our mutual intent to establish the GOs Network formally, and to describe our shared vision for its future. The views expressed here are ours alone as individual scientists, and do not necessarily represent those of the institutions with which we are affiliated.
Three-dimensional reconnection is much more diverse than two-dimensional reconnection. In deed, the characteristics of these two types of reconnection are very different. For instance, ...three-dimensional reconnection can occur both in the vicinity of null points, as well as in the absence of null points, whereas two-dimensional reconnection must occur at null points. Since, in two-dimensions reconnection only occurs at a single point, at most one pair of field lines can be reconnected to form a new pair of field lines at any instant in time. In three dimensions, however, there is a finite diffusion volume in which many field lines can be processed simultaneously. For the entire time that a portion of a field line is in the diffusion volume it will reconnect continuously and continually with all the other field lines it meets. This means that in three-dimensions field lines do not reconnect in pairs of lines making understanding three-dimensional reconnection difficult. In this chapter, we review the characteristics of two-dimensional and three-dimensional reconnection in more detail and also discuss some of the consequences of these characteristics. It is well know that the magnetic fields that thread the Sun’s surface cover a wide range of scales from tiny intranetwork features of just 1016 Mx up to sunspots with 1023 Mx of flux. There is an extensive mix of features of opposite polarities and scales which carpet the Sun. However, unlike a carpet the pattern is not static, and these features are highly dynamic. This inevitably leads to a complex and highly structured magnetic field in the solar atmosphere. It has been thought that null points rarely occurred in the solar atmosphere’s complex magnetic field, however, we show here that null points can readily occur. Furthermore, by studying the magnetic topology of a flux emergence experiment we reveal that reconnection occurring at separators linking two clusters of nulls is the mechanism by which the newly emerged flux interacts with the pre-existing flux in the solar atmosphere. Furthermore, we show that separator reconnection occurs along the length of the separator and not at the nulls at the ends of the separator. Thus, if a separator reaches up into the corona, even if its null points reside below the corona, it can be an important site for reconnection and thus a site of coronal heating.
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