Interface mobility from interface random walk     

Trautt ZT  Upmanyu M  Karma A 《Science (New York, N.Y.)》2006,314(5799):632-635

Computational studies aimed at extracting interface mobilities require driving forces orders of magnitude higher than those occurring experimentally. We present a computational methodology that extracts the absolute interface mobility in the zero driving force limit by monitoring the one-dimensional random walk of the mean interface position along the interface normal. The method exploits a fluctuation-dissipation relation similar to the Stokes-Einstein relation, which relates the diffusion coefficient of this Brownian-like random walk to the interface mobility. Atomic-scale simulations of grain boundaries in model crystalline systems validate the theoretical predictions and highlight the profound effect of impurities. The generality of this technique, combined with its inherent spatiotemporal efficiency, should allow computational studies to effectively complement experiments in understanding interface kinetics in diverse material systems.  相似文献   

A SUMOylation-dependent transcriptional subprogram is required for Myc-driven tumorigenesis     

Kessler JD  Kahle KT  Sun T  Meerbrey KL  Schlabach MR  Schmitt EM  Skinner SO  Xu Q  Li MZ  Hartman ZC  Rao M  Yu P  Dominguez-Vidana R  Liang AC  Solimini NL  Bernardi RJ  Yu B  Hsu T  Golding I  Luo J  Osborne CK  Creighton CJ  Hilsenbeck SG  Schiff R  Shaw CA  Elledge SJ  Westbrook TF 《Science (New York, N.Y.)》2012,335(6066):348-353

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Effects of forest stand type on oribatid mite (Acari: Oribatida) assemblages in a southwestern Quebec forest     

Zachary A. Sylvain  Christopher M. Buddle 《Pedobiologia》2010,53(5):321-325

Despite the ubiquity of oribatid mites in soil and litter systems, and their importance in decomposition and nutrient cycling processes, little is known of the factors underlying the composition of their assemblages. Our objective was to address this by determining how oribatid assemblage composition changes by forest stand type. This work was done in and near a hardwood forest in southwestern Quebec, Canada. We sampled mites by collecting 1 L of litter and 170 cm³ of soil from four sites in each of four distinct habitat types: American beech stands, sugar maple stands, mixed deciduous stands and mixed conifer plantations. Samples were collected in July and September 2005, and June 2006, and over 6500 oribatid mites were collected and identified to species. Abundance and species richness differed between forest types: for abundance conifer>beech>maple>mixed deciduous while for species richness beech and conifer>maple>mixed deciduous. Ordination analyses revealed that conifer plantations and beech stands supported distinct assemblages, while there were some overlap in the assemblages found in maple stands and mixed deciduous stands. These data support the importance of aboveground plant communities in affecting the composition of oribatid assemblages even at local scales and provide insight into additional impacts that may be caused by shifts in plant species ranges due to global changes.  相似文献   

Multidimensional drug profiling by automated microscopy     

Perlman ZE  Slack MD  Feng Y  Mitchison TJ  Wu LF  Altschuler SJ 《Science (New York, N.Y.)》2004,306(5699):1194-1198

We present a method for high-throughput cytological profiling by microscopy. Our system provides quantitative multidimensional measures of individual cell states over wide ranges of perturbations. We profile dose-dependent phenotypic effects of drugs in human cell culture with a titration-invariant similarity score (TISS). This method successfully categorized blinded drugs and suggested targets for drugs of uncertain mechanism. Multivariate single-cell analysis is a starting point for identifying relationships among drug effects at a systems level and a step toward phenotypic profiling at the single-cell level. Our methods will be useful for discovering the mechanism and predicting the toxicity of new drugs.  相似文献   

Concurrent use of rabacfosadine and L-asparaginase for relapsed or refractory multicentric lymphoma in dogs     

Jacob R. Cawley  Zachary M. Wright  Karri Meleo  Gerald S. Post  Craig A. Clifford  Kathryn R. Vickery  David M. Vail  Philip J. Bergman  Douglas H. Thamm 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2020,34(2):882-889

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Three-dimensional bladder ultrasound for estimation of urine volume in dogs compared with traditional 2-dimensional ultrasound methods     

Allison Kendall  Erin Keenihan  Zachary T. Kern  Crystal Lindaberry  Adam Birkenheuer  George E Moore  Shelly L. Vaden 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2020,34(6):2460-2467

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Kettle holes reflect the biogeochemical characteristics of their catchment area and the intensity of the element-specific input     

Nitzsche  Kai Nils  Kleeberg  Andreas  Hoffmann  Carsten  Merz  Christoph  Premke  Katrin  Gessler  Arthur  Sommer  Michael  Kayler  Zachary E. 《Journal of Soils and Sediments》2022,22(3):994-1009

Journal of Soils and Sediments - Kettle holes are small inland water bodies known to be dominated by terrigenous material; however, the processes and structures that drive the enrichment and...  相似文献   

Peroxiredoxin evolution and the regulation of hydrogen peroxide signaling   总被引：3，自引：0，他引：3  

Wood ZA  Poole LB  Karplus PA 《Science (New York, N.Y.)》2003,300(5619):650-653

Eukaryotic 2-Cys peroxiredoxins (2-Cys Prxs) not only act as antioxidants, but also appear to regulate hydrogen peroxide-mediated signal transduction. We show that bacterial 2-Cys Prxs are much less sensitive to oxidative inactivation than are eukaryotic 2-Cys Prxs. By identifying two sequence motifs unique to the sensitive 2-Cys Prxs and comparing the crystal structure of a bacterial 2-Cys Prx at 2.2 angstrom resolution with other Prx structures, we define the structural origins of sensitivity. We suggest this adaptation allows 2-Cys Prxs to act as floodgates, keeping resting levels of hydrogen peroxide low, while permitting higher levels during signal transduction.  相似文献   

Burrowing behaviour of unionid mussels in subtropical rivers: Implications for survey guidelines     

Bianca A. Hernández  Zachary A. Mitchell  Clinton R. Robertson  Astrid N. Schwalb 《水产资源保护:海洋与淡水生态系统》2021,31(4):903-915

1. Conservation efforts have increased in response to global mussel declines, and effective surveys are a crucial step in assessing and monitoring mussel populations and in determining their conservation status. The burrowing behaviour of mussels can affect their detectability, and a better understanding of these behaviours would help to improve survey design and guidelines.
2. The burrowing depth of mussels may differ between seasons, habitat conditions, species, and individuals, and little is known about the burrowing behaviour of mussels in subtropical rivers.
3. Burrowing depth variation was examined and compared at three sites in the San Marcos, Guadalupe, and San Antonio river drainages in central Texas. In addition, laboratory experiments were used to determine whether observed differences between field sites and seasons could be linked to differences in substrate type and water temperature and to examine differences between species.
4. Seasonal variation in burrowing depth was found at all field sites, and water temperature was a significant factor for explaining variation in burrowing depth, but there was no clear relationship between burrowing depth and temperature in shorter term laboratory experiments, where individual variation was high and burrowing behaviour seemed to be solely a function of time.
5. Mussels burrowed significantly deeper in finer substrate (sand vs. gravel) in both field and laboratory experiments. Few significant differences between species were found in the field, but no differences were found in the laboratory experiments.
6. The results suggest that surveys may need to follow different guidelines depending on local conditions, such as substrate and water temperature. Surveys will be less efficient and may fail to detect larger proportions of populations in colder water temperatures. In addition, a larger proportion of burrowed mussels can be expected at sites with finer substrate, such as sand. Under these conditions, visual searches will not suffice, as a large part of the population or specific species may be overlooked.

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Dependence of heterochromatic histone H3 methylation patterns on the Arabidopsis gene DDM1     

Gendrel AV  Lippman Z  Yordan C  Colot V  Martienssen RA 《Science (New York, N.Y.)》2002,297(5588):1871-1873

The Arabidopsis gene DDM1 is required to maintain DNA methylation levels and is responsible for transposon and transgene silencing. However, rather than encoding a DNA methyltransferase, DDM1 has similarity to the SWI/SNF family of adenosine triphosphate-dependent chromatin remodeling genes, suggesting an indirect role in DNA methylation. Here we show that DDM1 is also required to maintain histone H3 methylation patterns. In wild-type heterochromatin, transposons and silent genes are associated with histone H3 methylated at lysine 9, whereas known genes are preferentially associated with methylated lysine 4. In ddm1 heterochromatin, DNA methylation is lost, and methylation of lysine 9 is largely replaced by methylation of lysine 4. Because DNA methylation has recently been shown to depend on histone H3 lysine 9 methylation, our results suggest that transposon methylation may be guided by histone H3 methylation in plant genomes. This would account for the epigenetic inheritance of hypomethylated DNA once histone H3 methylation patterns are altered.  相似文献