712 research outputs found
The relationship between upper mantle anisotropic structures beneath California, transpression, and absolute plate motions
We calculated SKS splitting parameters for the California Integrated Seismic Network. In southern California, we also estimated splitting in the upper 100 km using azimuthal anisotropy determined from surface waves. The inferred splitting from surface waves in the mantle lithosphere is small (on average < 0.2 s) compared with SKS splitting (1.5 s) and obtains a maximum value (0.5 s) in the transpressive region of the Big Bend, south of, and aligned with, the San Andreas Fault (SAF). In contrast, the SKS splitting is approximately E-W and is relatively uniform spatially either side of the Big Bend of the SAF. These differences suggest that most of the SKS splitting is generated much deeper (down to 300–400 km) than previously thought, probably in the asthenosphere. Fast directions align with absolute plate motions (APM) in northern and southeastern California but not in southwestern California. We interpret the parallelism with APM as indicating the SKS anisotropy is caused by cumulative drag of the asthenosphere by the overlying plates. The discrepancy in southwestern California arises from the diffuse boundary there compared to the north, where relative plate motion has concentrated near the SAF system. In southern California the relative motion originated offshore in the Borderlands and gradually transitioned onshore to the SAF system. This has given rise to smaller displacement across the SAF (160–180 km) compared with central and northern California (400–500 km). Thus, in southwestern California the inherited anisotropy, from prior North American APM, has not yet been overprinted by Pacific APM
Floral stem cell termination involves the direct regulation of AGAMOUS by PERIANTHIA
In Arabidopsis, the population of stem cells present in young flower buds is lost after the production of a fixed number of floral organs. The precisely timed repression of the stem cell identity gene WUSCHEL (WUS) by the floral homeotic protein AGAMOUS (AG) is a key part of this process. In this study, we report on the identification of a novel input into the process of floral stem cell regulation. We use genetics and chromatin immunoprecipitation assays to demonstrate that the bZIP transcription factor PERIANTHIA (PAN) plays a role in regulating stem cell fate by directly controlling AG expression and suggest that this activity is spatially restricted to the centermost region of the AG expression domain. These results suggest that the termination of floral stem cell fate is a multiply redundant process involving loci with unrelated floral patterning functions
Whorl-Specific Expression of the SUPERMAN Gene of Arabidopsis Is Mediated by cis Elements in the Transcribed Region
The SUPERMAN (SUP) gene of Arabidopsis is involved in controlling cell proliferation in stamen and carpel primordia and in ovules during flower development. The SUP gene encodes a transcription factor with a C2H2-type zinc finger motif, a serine/proline-rich domain, a basic domain, and a leucine-zipper-like domain and is expressed in a very limited region in stamen primordia and in the developing ovary during flower development. The SUP gene is susceptible to methylation, resulting in epigenetic gene silencing. To understand how the SUP gene is expressed spatially and temporally in its restricted domain, and why methylation of the transcribed region affects early-stage SUP expression, we have identified the SUP cis regulatory elements by characterizing SUP gene fusions. These studies show that the SUP gene has discrete upstream promoter elements required for expression in stamen primordia in early stages and in the ovary in later stages. The promoter activity for stamen primordia is modulated by several positive and negative elements located in the transcribed and translated regions. Several regulatory elements in the transcribed region correlate with the areas of the gene that are heavily methylated in epigenetic alleles; these data provide a possible explanation of how methylation of the transcribed region represses transcription
Electronic-Structure-Driven Magnetic Ordering in a Kondo Semiconductor CeOs2Al10
We report the anisotropic changes in the electronic structure of a Kondo
semiconductor CeOsAl across an anomalous antiferromagnetic ordering
temperature () of 29 K, using optical conductivity spectra. The spectra
along the - and -axes indicate that a - hybridization gap emerges
from a higher temperature continuously across . Along the b-axis, on the
other hand, a different energy gap with a peak at 20 meV appears below 39 K,
which is higher temperature than , because of structural distortion. The
onset of the energy gap becomes visible below . Our observation reveals
that the electronic structure as well as the energy gap opening along the
b-axis due to the structural distortion induces antiferromagnetic ordering
below .Comment: 4 pages, 4 figure
Effect of Humidity on Vibrational Properties of Chemically Modified Wood
Changes in vibrational properties of wood can be used to determine changes in the wood cell wall resulting from chemical modification. The dynamic Young's modulus to specific gravity ratio (E'/γ) and internal friction (tan δ) for chemically modified wood compared to those for untreated wood showed major differences in cell-wall modification and lumen filling modification. Increasing the moisture content of the cell wall also has a major effect on the vibrational properties of chemically modified wood. In general, treatments that resulted in lowering the moisture content of the cell wall also lowered internal friction within the cell wall. Vapor phase reactions with formaldehyde had the greatest effect in stabilizing the cell wall against changes in dynamic mechanical properties with increasing moisture content
New BPS Solitons in 2+1 Dimensional Noncommutative CP^1 Model
Investigating the solitons in the non-commutative model, we have
found a new set of BPS solitons which does not have counterparts in the
commutative model.Comment: 8 pages, LaTeX2e, references added, improvements to discussions,
Version to be published in JHE
The Spatial Signature of Biotic Interactions of a Clonal and a Non-clonal Palmetto in a Subtropical Plant Community
Spatial analyses of plant-distribution patterns can provide inferences about intra- and interspecific biotic interactions. Yet, such analyses are rare for clonal plants because effective tools (i.e., molecular markers) needed to map naturally occurring clonal individuals have only become available recently. Clonal plants are unique in that a single genotype has a potential to spatially place new individuals (i.e., ramets) in response to intra- and interspecific biotic interactions. Laboratory and greenhouse studies suggest that some clonal plants can avoid intra-genet, inter-genet, and inter-specific competition via rootplacement patterns. An intriguing and yet to be explored question is whether a spatial signature of such multi-level biotic interactions can be detected in natural plant communities. The facultatively clonal Serenoa repens and non-clonal Sabal etonia are ecologically similar and co-dominant palmettos that sympatrically occur in the Florida peninsula. We used amplified fragment length polymorphisms (AFLPs) to identify Serenoa genets and also to assign field-unidentifiable small individuals as Sabal seedlings, Serenoa seedlings, or Serenoa vegetative sprouts. Then, we conducted univariate and bivariate multi-distance spatial analyses to examine the spatial interactions of Serenoa (n=271) and Sabal (n=137) within a 20x20 m grid at three levels, intragenet, intergenet and interspecific. We found that spatial interactions were not random at all three levels of biotic interactions. Serenoa genets appear to spatially avoid self-competition as well as intergenet competition. Furthermore, Serenoa and Sabal were spatially negatively associated with each other. However, this negative association pattern was also evident in a spatial comparison between non-clonal Serenoa and Sabal, suggesting that Serenoa genets’ spatial avoidance of Sabal through placement of new ramets is not the explanation of the interspecific-level negative spatial pattern. Our results emphasize the importance of investigating spatial signatures of biotic as well as abiotic interactions at multiple levels in understanding spatial distribution patterns of clonal plants in natural plant communities
The BAT-Swift Science Software
The BAT instrument tells the Swift satellite where to point to make immediate
follow-up observations of GRBs. The science software on board must efficiently
process gamma-ray events coming in at up to 34 kHz, identify rate increases
that could be due to GRBs while disregarding those from known sources, and
produce images to accurately and rapidly locate new Gamma-ray sources.Comment: 4 pages, no figures, to appear in Santa Fe proceedings "Gamma-Ray
Bursts: 30 Years of Discovery", Fenimore and Galassi (eds), AIP, 200
Extensive clonal spread and extreme longevity in saw palmetto, a foundation clonal plant
The lack of effective tools have hampered our ability to assess the size, growth and ages of clonal plants. With Serenoa repens (saw palmetto) as a model, we introduce a novel analytical framework that integrates DNA fingerprinting and mathematical modelling to simulate growth and estimate ages of clonal plants. We also demonstrate the application of such life-history information of clonal plants to provide insight into management plans. Serenoa is an ecologically important foundation species in many Southeastern United States ecosystems; yet, many land managers consider Serenoa a troublesome invasive plant. Accordingly, management plans have been developed to reduce or eliminate Serenoa with little understanding of its life history. Using Amplified Fragment Length Polymorphisms, we genotyped 263 Serenoa and 134 Sabal etonia (a sympatric non-clonal palmetto) samples collected from a 20 X 20 m study plot in Florida scrub. Sabal samples were used to assign small field-unidentifiable palmettos to Serenoa or Sabal and also as a negative control for clone detection. We then mathematically modelled clonal networks to estimate genet ages. Our results suggest that Serenoa predominantly propagate via vegetative sprouts and 10000-year-old genets may be common, while showing no evidence of clone formation by Sabal. The results of this and our previous studies suggest that: (i) Serenoa has been part of scrub associations for thousands of years, (ii) Serenoa invasion are unlikely and (ii) once Serenoa is eliminated from local communities, its restoration will be difficult. Reevaluation of the current management tools and plans is an urgent task
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