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• The specification of the meristem/organ boundary is critical for plant development. Here, we investigate two previously uncharacterized NAC transcription factors: the first, OsCUC1, which is negatively regulated by osa-miR164c, dimerizes with the second, OsCUC3, and functions partially redundantly in meristem/organ boundary specification in rice (Oryza sativa). • We produced knockout lines for rice OsCUC1 (the homolog of Arabidopsis CUC1 and CUC2) and OsCUC3 (the homolog of Arabidopsis CUC3), as well as an overexpression line for osa-miR164c, to study the molecular mechanism of boundary specification in rice. • A single mutation in either OsCUC1 or OsCUC3 leads to defects in the establishment of the meristem/organ boundary, resulting in reduced stamen numbers and the fusion of leaves and filaments, and the defects are greatly enhanced in the double mutant. Transgenic plants overexpressing osa-miR164c showed a phenotype similar to that of the OsCUC1 knockout line. In addition, knockout of OsCUC1 leads to multiple defects, including dwarf plant architecture, male sterility and twisted-rolling leaves. Further study indicated that OsCUC1 physically interacts with leaf-rolling related protein CURLED LEAF AND DWARF 1 (CLD1) and stabilizes it in the nucleus to control leaf morphology. • This work demonstrated that the interplay of osa-miR164c, OsCUC1 and OsCUC3 controls boundary specification in rice.

Missing data caused by boundary specification has a detrimental effect on the analysis of network structures, and designing optimal sampling methods is crucial for conducting network investigations. The present study discusses the boundary specification problem in multiple surveys, and proposes a mathematical model for optimizing the sampling strategy in each independent survey. A memetic algorithm that maximizes the sample representativeness is proposed as well, and experiments have proved the effectiveness and efficiency of the proposed algorithm. Zachary’s Karate Club network and three networks of migrant workers are also performed to explain the social meaning of the optimal sampling method.

Background In  Arabidopsis , the genes SHOOT MERISTEMLESS  ( STM ) and  CLAVATA 3 ( CLV3 ) antagonistically regulate shoot meristem development. STM is essential for both development and maintenance of the meristem, as  stm  mutants fail to develop a shoot meristem. CLV3, on the other hand, negatively regulates meristem proliferation, and  clv3  mutants possess an enlarged shoot meristem. Genetic interaction studies revealed that  stm  and  clv3 dominantly suppress each other’s phenotypes. STM works in conjunction with its closely related homologue KNOTTED1-LIKE HOMEOBOX GENE 6 (KNAT6) to promote meristem development and organ separation, as  stm   knat6  double mutants fail to form shoot meristem and produce a fused cotyledon. Results In this study, we show that  clv3  fails to promote shoot meristem formation in  stm-1  background if we also remove KNAT6.  stm-1   knat6 clv3  triple mutants result in shoot meristem termination and produce fused cotyledons similar to  stm   knat6  double mutant. Notably, the stm-1 knat6 and stm-1 knat6 clv3 alleles lack tissue in the presumed region of SAM that is a novel phenotype reported in Arabidopsis mutants.  stm-1   knat6 clv3  also showed reduced inflorescence size as compared to  clv3  single or  stm   clv3  double mutants. Conclusion In contrast to previously published data, these data suggest that STM and KNAT6 are redundantly required for the vegetative SAM, but insufficient for the inflorescence meristem.

Despite the well-known dependence of vertex and network structural parameters on network boundary specification employed by researchers, there has so far been effectively no discussion of this methodological caveat in the global and world city literature. Given the reliance of empirical studies of urban networks on the sampling of underlying actors that form these networks by their interactions, we consider it of key importance to examine the dependence of network centralities of cities on network boundary specification. We consider three distinctive modelling approaches based on: (a) office networks, (b) ownership ties and (c) inter-organisational projects. Our results indicate that city network centralities obtained from sampled networks are highly consistent with those obtained from whole network analysis for samples featuring as little as 4% (office networks), 10% (ownership ties) and 25% (inter-organisational projects) of the underlying actors.

This chapter first discusses the types of missing network data and the methods of treating such data before partitioning. Errors in social network research design can be divided into three broad categories: boundary specification problems, questionnaire design, and errors due to respondents. The first two categories belong in the domain of researchers responsible for designing the best possible data collection instruments and being careful in the selection of respondents. The third category consists of errors due solely to actors regardless of instrument design. The chapter also focuses on treatments of missing data due to actor non‐response. The impacts of the non‐response treatments are based on clustering three distinct real networks after each has been subjected to actor non‐response. The chapter reviews briefly the basic distinction between indirect and direct blockmodeling. It presents the basic design of simulations and discusses the nature of the real networks used for the simulation study.

This chapter contains sections titled: Connecting Light Interference with Basic Optical Concepts Light Sources Interference Interferometers Diffraction of the Light References

The structure and the frequency spectra of wall pressure fluctuations beneath a planar turbulent boundary layer interacting with a conical shock wave at Mach number $M_\\infty =2.05$ and Reynolds number $\\textit {Re}_\\theta \\approx 630$ (based on the upstream boundary layer momentum thickness) are examined to elucidate the effects of pressure gradient and flow separation on the characteristics of the wall pressure fluctuations, by exploiting a direct numerical simulation database. Upstream of the interaction, in the zero pressure gradient region, wall pressure statistics compare well with canonical compressible boundary layers in terms of fluctuation intensities and frequency spectra. Across the main interaction zone (APG1), the root-mean-square of wall pressure fluctuations becomes very large (corresponding to approximately 173.3 dB), with maximum increase approximately 12.7 dB from the incoming level. In the second adverse pressure gradient zone (APG2), the root-mean-square of wall pressure fluctuations attains a second peak (corresponding to $164.7$ dB), with an increase of 8.4 dB from the upstream level. Both the APG1 and APG2 regions feature a substantial fraction of flow reversal events, which are, however, scattered and interspersed with regions of attached flow. The wall pressure power spectral density exhibits a broadband and energetic low-frequency component associated with the global unsteadiness of the separation bubble/conical shock system. Analysis of the two-point correlations and wavenumber/frequency spectra of wall pressure fluctuations further suggests that the typical eddies become more elongated along the spanwise direction, as the flow in the separated region tends to escape the centreline, and the convection velocity is significantly reduced.

Pluripotent embryonic stem cells (ESCs) can differentiate into any adult cell type; however, aggregates of these cells do not mimic embryonic architecture when grown in culture. To see whether mouse ESCs and their extraembryonic counterparts, trophoblast stem cells (TSCs), can recapitulate normal development, Harrison et al. combined ESCs and TSCs in an extracellular matrix culture (see the Perspective by Pera). The resultant “ETS-embryos” displayed considerable resemblance to normal embryos, even specifying mesoderm and primordial germ cells at the boundary between embryonic and extraembryonic compartments. These ETS-embryos are a genetically tractable tool for studying mammalian embryogenesis. Science , this issue p. eaal1810 ; see also p. 137 Embryonic and trophoblast stem cells self-assemble to generate a structure resembling a natural mouse embryo. Mammalian embryogenesis requires intricate interactions between embryonic and extraembryonic tissues to orchestrate and coordinate morphogenesis with changes in developmental potential. Here, we combined mouse embryonic stem cells (ESCs) and extraembryonic trophoblast stem cells (TSCs) in a three-dimensional scaffold to generate structures whose morphogenesis is markedly similar to that of natural embryos. By using genetically modified stem cells and specific inhibitors, we show that embryogenesis of ESC- and TSC-derived embryos—ETS-embryos—depends on cross-talk involving Nodal signaling. When ETS-embryos develop, they spontaneously initiate expression of mesoderm and primordial germ cell markers asymmetrically on the embryonic and extraembryonic border, in response to Wnt and BMP signaling. Our study demonstrates the ability of distinct stem cell types to self-assemble in vitro to generate embryos whose morphogenesis, architecture, and constituent cell types resemble those of natural embryos.

A network approach helps us better specify and model collaboration among people involved in organized crime. The focus on collaboration raises the boundary specification problem: Where do criminal organizations start, where do they end, and who is involved? Traditional approaches sometimes assume the existence of simple, rigid structures when complexity and fluidity are the norms. A network approach embraces this complexity conceptually and provides methodological guidelines for clarifying boundaries. Boundary specification in organized crime helps solve four puzzles. First, social boundaries: a network approach reduces confusion about social boundaries as criminal entrepreneurs interact with criminals and noncriminals in diverse contexts, only some of them illicit. Second, boundaries of group membership: network data and methods obviate the need for formal membership attributions. Third, ethnic boundaries network analyses reveal that the effective boundaries of criminal organizations are based on social relations, not attributes such as ethnicity. Fourth, recruitment: attending to the larger social environments in which organizations are embedded provides a clearer view of how mechanisms of recruitment cross seemingly rigid boundaries between members and prospective members.

The inner ear contains distinct sensory organs, produced sequentially by segregation from a large sensory-competent domain in the developing otic vesicle. To understand the mechanistic basis of this process, we investigated the changes in prosensory cell patterning, proliferation, and character during the segregation of some of the vestibular organs in the mouse and chicken otic vesicle. We discovered a specialised boundary domain, located at the interface of segregating organs. It is composed of prosensory cells that gradually enlarge, elongate, and are ultimately diverted from a prosensory fate. Strikingly, the boundary cells align their apical borders and constrict basally at the interface of cells expressing or not the Lmx1a transcription factor, an orthologue of Drosophila Apterous. The boundary domain is absent in Lmx1a -deficient mice, which exhibit defects in sensory organ segregation and is disrupted by the inhibition of ROCK-dependent actomyosin contractility. Altogether, our results suggest that actomyosin-dependent tissue boundaries ensure the proper separation of inner ear sensory organs and uncover striking homologies between this process and the compartmentalisation of the Drosophila wing disc by lineage-restricted boundaries.