Plasmodesmata permit solutes to move between cells nonspecifically and without having to cross a membrane. This symplastic connectivity, while straightforward to observe using fluorescent tracers, ...has proven difficult to quantify. We use fluorescence recovery after photobleaching, combined with a mathematical model of symplastic diffusion, to assay plasmodesmata-mediated permeability in the Arabidopsis (Arabidopsis thaliana) root meristem in wild-type and transgenic lines, and under selected chemical treatments. The permeability measured for the wild type is nearly 10-times greater than previously reported. Plamodesmal permeability remains constant in seedlings treated with auxin (30 mM indoleacetic acid for 2 and 24 h; 100 nm indoleacetic acid for 2 h); however, permeability is diminished in two lines previously reported to have impaired plasmodesmal function as well as in wild-type seedlings treated for 24 h with 0.6 mM tryptophan. Moreover, plasmodesmal permeability is strongly altered by applied hydrogen peroxide within 2 h of treatment, being approximately doubled at a low concentration (0.6 mM) and nearly eliminated at a higher one (6 mM). These results reveal that the plasmodesmata in the root meristem carry a substantial flux of small molecules and that this flux is subject to rapid regulation.
Researchers on travel behavior and regional economic trends increasingly rely on multiple data sources to locate employers and site-specific employment. In a previous study, we proposed a method to ...assess and integrate multiple sources of employment data using three components: the Google Places application programming interface (API), a business existence verification model, and manual reviews of sampled data. This paper updates our previous methodology with a dual conditional classification of incoming and previously verified employment data made possible by checks using Google Places API and two rounds of string comparisons for both business names and establishment locations. The resulting match classes distinguish well-matched or confirmed business listings from those that require additional review to evaluate potential business closure or relocation. This screening process, augmented with fuzzy logic string matching techniques, reduces the effort needed to update employer information and assists with automated data standardization and deduplication, integrating incoming employment information with a database of verified employers.
Organizations increasingly use forms of temporary organizing to achieve business goals. In the academic debate on temporary organizing the relationship between the temporary and the parent ...organization has so far remained underexposed. This paper uses modularity theory and the deployment strategy of the Dutch Armed Forces as a starting point to explore this relationship. Especially organizations that frequently participate in inter-organizational projects and contribute larger organizational elements to these temporary structures can benefit from the research findings. The results confirm that the so much desired plug-and-play character of a modular system is difficult to achieve in a social system, making it necessary for organizations to put extra effort in standardization, co-ordination and socialization capabilities.
Focusing on 35 American migrants' experiences in mainland China, this study provides a new conceptual understanding of international migrants' Other-identity formulated in and through intercultural ...encounters. Guided by grounded theory, this study demonstrates that American migrants' Otherness was frequently triggered by their divergences from Chinese cultural values' emphasis on individuals' conformity to interdependence, group interests, group cohesiveness, homogeneity and unequally distribution of power and status within a social structure. As the Other in mainland China, American migrants adapted themselves to Chinese society via diverse strategic positioning, which eventually contributed to the differential formation of an integrated identity during immigration.
Models of plant growth and development propose that changes in cell polarity are mediated by gradients of the plant hormone auxin. With use of gas chromatography-mass spectrometry, we measured the ...redistribution of endogenous auxin in stems of quaking apen trees (Populus tremuloides) after wounding. Persistent (lasting at least 24 hours) auxin gradients were observed in the region of the cambium where cell polarity was changing. A computer model of the auxin redistribution shows agreement with measured concentrations.
We consider whether the observed periodicity of mass extinctions and of comet impacts on Earth is consistent with Solar oscillation about the Galactic midplane and spiral arm crossings. It is of ...further interest to determine whether a hypothetical thin dark disk is necessary to give the right periodicity, and whether such a dark disk is allowed given kinematic and other observational constraints on the Galaxy’s gravitational potential. We show that a dark disk consistent with recent bounds, combined with data for spiral arm crossing, can lead to the required periodicity. Moreover, we find that the best fit values correctly predict the date of the Chicxulub crater dated to 66 My ago.
The beautiful patterns apparent in wood grain have their origin in the alignment of fusiform initial cells in the vascular cambium of trees. We develop a mathematical model to describe the ...orientation of fusiform initial cells, and their interaction with the plant hormone indole-3-acetic acid (auxin). The model incorporates the following four assumptions: (1) auxin is actively transported parallel to the long axis of the initials, (2) auxin diffuses perpendicular to the long axis of the initials, (3) the initials tend to orient parallel to the flux of auxin through the cambium, and (4) adjacent initials tend to orient parallel to one another. Each assumption is justified on the basis of available evidence and cast in mathematical form. Our main result is a pair of nonlinear differential equations that describe the coupling between the distribution of auxin in the cambium and the orientation of fusiform initials. Numerical solutions to the equations show qualitative resemblance to the wood grain patterns observed at branch junctions, wounds and knots, and topological defects.
Superconducting detectors have been proposed as outstanding targets for the direct detection of light dark matter scattering at masses as low as a keV. We study the prospects for directional ...detection of dark matter in isotropic superconducting targets from the angular distribution of excitations produced in the material. We find that dark matter scattering produces initial excitations with an anisotropic distribution, and further show that this directional information can be preserved as the initial excitations relax. Our results demonstrate that directional detection is possible for a wide range of dark matter masses, and they pave the way for light dark matter discovery with bulk superconducting targets.
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