Leaves and flowers begin life as outgrowths from the edges of shoot apical meristems. Stem cell divisions in the meristem center replenish cells that are incorporated into organ primordia at the meristem periphery and leave the meristem. Organ boundaries, regions of limited growth that separate forming organs from the meristem, serve to isolate these two domains and are critical for coordination of organogenesis and meristem maintenance. Boundary formation and maintenance are poorly understood processes, despite the identification of a number of boundary-specific transcription factors. Here we provide genetic and biochemical evidence that the Arabidopsis thaliana transcription factor LATERAL ORGAN BOUNDARIES (LOB) negatively regulates accumulation of the plant steroid hormone brassinosteroid (BR) in organ boundaries. We found that ectopic expression of LOB results in reduced BR responses. We identified BAS1, which encodes a BR-inactivating enzyme, as a direct target of LOB transcriptional activation. Loss-of-function lob mutants exhibit organ fusions, and this phenotype is suppressed by expression of BAS1 under the LOB promoter, indicating that BR hyperaccumulation contributes to the lob mutant phenotype. In addition, LOB expression is BR regulated; therefore, LOB and BR form a feedback loop to modulate local BR accumulation in organ boundaries to limit growth in the boundary domain.L eaves and flowers are produced from the periphery of the shoot apical meristem, a self-perpetuating structure containing a population of self-renewing stem cells. Stem cell divisions in the meristem center replenish the cells that are incorporated into organ primordia at the meristem periphery and exit the meristem (1). The balance between organogenesis and meristem maintenance is essential for continued organ formation, and the boundary between the meristem and organ primordia plays a key role in maintaining the integrity of the meristem and differentiating organs. Boundary cells are small and divide infrequently relative to cells in the adjacent regions; thus, the boundary is a discrete domain that is distinct from the meristem and organ primordia (2-4). During organ formation, inhibition of growth in the boundary allows formation of a cleft, which results in separation of the forming organ from the meristem. A number of boundary-specific transcription factors in several families act redundantly to specify organ boundary cell fate and meristem maintenance (5-11). Few targets of boundary-specific transcription factors have been identified, and little is known about the physiological and biochemical processes they regulate.Arabidopsis LATERAL ORGAN BOUNDARIES (LOB) encodes a member of the plant-specific LOB-domain transcription factor family and is expressed specifically in organ boundaries (12). To investigate the developmental function of LOB, we examined the consequence of increased and decreased LOB activity and used expression profiling to identify targets of LOB transcriptional regulation. We show that LOB negatively regulate...

Control of competing parameters such as thermoelectric (TE) power and electrical and thermal conductivities is essential for the high performance of thermoelectric materials. Bulk-nanocomposite materials have shown a promising improvement in the TE performance due to poor thermal conductivity and charge carrier filtering by interfaces and grain boundaries. Consequently, it has become pressingly important to understand the formation mechanisms, stability of interfaces and grain boundaries along with subsequent effects on the physical properties. We report here the effects of the thermodynamic environment during spark plasma sintering (SPS) on the TE performance of bulk-nanocomposites of chemically synthesized Bi(2)Te(2.7)Se(0.3) nanoplatelets. Four pellets of nanoplatelets powder synthesized in the same batch have been made by SPS at different temperatures of 230, 250, 280, and 350 °C. The X-ray diffraction, transmission electron microscopy, thermoelectric, and thermal transport measurements illustrate that the pellet sintered at 250 °C shows a minimum grain growth and an optimal number of interfaces for efficient TE figure of merit, ZT∼0.55. For the high temperature (350 °C) pelletized nanoplatelet composites, the concurrent rise in electrical and thermal conductivities with a deleterious decrease in thermoelectric power have been observed, which results because of the grain growth and rearrangements of the interfaces and grain boundaries. Cross section electron microscopy investigations indeed show significant grain growth. Our study highlights an optimized temperature range for the pelletization of the nanoplatelet composites for TE applications. The results provide a subtle understanding of the grain growth mechanism and the filtering of low energy electrons and phonons with thermoelectric interfaces.

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We investigated the effect of international collaboration (in the form of international co-authorship) on the impact of publications of young universities (<50 years old), and compared to that of renowned old universities (>100 years old). The following impact indicators are used in this study, they are: (1) the 5-year citations per paper (CPP) data, (2) the international co-authorship rate, (3) the CPP differential between publications with and without international co-authorships, and (4) the difference between the percentage of international co-authored publications falling in the global top 10 % highly cited publications and the percentage of overall publications falling in the global top 10 % highly cited publications (Δ%Top10%). The increment of 5-year (2010–2014) field weighted citation impact (FWCI) of internationally co-authored papers over the 5-year overall FWCI of the institutions in SciVal® is used as another indicator to eliminate the effect of discipline difference in citation rate. The results show that, for most top institutions, the difference between the citations per paper (CPP) for their publications with and without international co-authorship is positive, with increase of up to 5.0 citations per paper over the period 1996–2003. Yet, for some Asian institutions, by attracting a lot of researchers with international background and making these collaborating “external” authors as internal researchers, these institutions have created a special kind of international collaboration that are not expressed in co-authorship, and the CPP gaps between publications with and without international co-authorship are relatively small (around 0–1 citations per paper increment) for these institutions. The top old institutions have higher CPP than young institutions, and higher annual research expenditures; while young universities have a higher relative CPP increment for the current 5-year period over the previous 5-year period. The Δ%Top10% for international co-authored publications is generally higher than that for all journal publications of the same institution. With the increase of international co-authorship ratio, the mean geographical collaboration distance (MGCD, an indication of increased international co-authorship) of one institution based on the Leiden Ranking data also increases, and young institutions have relatively higher CPP increment over MGCD increment. International co-authorship has a positive contribution to the FWCI of the institution, yet there are untapped potential to enhance the collaboration among young institutions.

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