A 3D radiative transfer framework: VII. Arbitrary velocity fields in the Eulerian frame

A solution of the radiative-transfer problem in 3D with arbitrary velocity fields in the Eulerian frame is presented. The method is implemented in our 3D radiative transfer framework and used in the PHOENIX/3D code. It is tested by comparison to our well- tested 1D co-moving frame radiative transfer code, where the treatment of a monotonic velocity field is implemented in the Lagrangian frame. The Eulerian formulation does not need much additional memory and is useable on state-of-the-art computers, even large-scale applications with 1000's of wavelength points are feasible

Hydrodynamic crystals: collective dynamics of regular arrays of spherical particles in a parallel-wall channel

Simulations of over $10^3$ hydrodynamically coupled solid spheres are performed to investigate collective motion of linear trains and regular square arrays of particles suspended in a fluid bounded by two parallel walls. Our novel accelerated Stokesian-dynamics algorithm relies on simplifications associated with the Hele--Shaw asymptotic far-field form of the flow scattered by the particles. The simulations reveal propagation of particle-displacement waves, deformation and rearrangements of a particle lattice, propagation of dislocation defects in ordered arrays, and long-lasting coexistence of ordered and disordered regions.Comment: 4 pages 6 figure

Visual attention in autism families: ‘unaffected’ sibs share atypical frontal activation

Background: In addition to their more clinically evident abnormalities of social cognition, people with autism spectrum conditions (ASC) manifest perturbations of attention and sensory perception which may offer insights into the underlying neural abnormalities. Similar autistic traits in ASC relatives without a diagnosis suggest a continuity between clinically affected and unaffected family members

Endolithic colonization of fluid inclusion trails in mineral grains

Many scenarios for the colonization of planetary surfaces by microbial life involve endoliths. This study records microbial mass along fluid inclusion trails (healed microfractures) in quartz grains

Differential Step Response of Unipolar Space-Charge-Limited Current in Solids

The small signal step response of unipolar space‐charge‐limited current in solids is analyzed for planar structures and for media in which the drift velocity of the charge carriers is either proportional to the electric field (thermal charge carriers) or is independent of the electric field (hot charge carriers). Results are reported in analytical and graphical form. Their features are discussed in terms of the underlying physical phenomena, as well as in the perspective of experimental applications. Cylindrical and spherical structures are not accessible to closed‐form solutions by the approach

Multiprocessor Approximate Message Passing with Column-Wise Partitioning

Solving a large-scale regularized linear inverse problem using multiple processors is important in various real-world applications due to the limitations of individual processors and constraints on data sharing policies. This paper focuses on the setting where the matrix is partitioned column-wise. We extend the algorithmic framework and the theoretical analysis of approximate message passing (AMP), an iterative algorithm for solving linear inverse problems, whose asymptotic dynamics are characterized by state evolution (SE). In particular, we show that column-wise multiprocessor AMP (C-MP-AMP) obeys an SE under the same assumptions when the SE for AMP holds. The SE results imply that (i) the SE of C-MP-AMP converges to a state that is no worse than that of AMP and (ii) the asymptotic dynamics of C-MP-AMP and AMP can be identical. Moreover, for a setting that is not covered by SE, numerical results show that damping can improve the convergence performance of C-MP-AMP.Comment: This document contains complete details of the previous version (i.e., arXiv:1701.02578v1), which was accepted for publication in ICASSP 201

Engineering Bureaucracy: The Genesis of Formal Policies, Positions, and Structures in High-Technology Firms

[Excerpt] This article examines the impact of organizational founding conditions on several facets of bureaucratization—managerial intensity, the proliferation of specialized managerial and administrative roles, and formalization of employment relations. Analyzing information on a sample of technology start-ups in California\u27s Silicon Valley, we characterize the organizational models or blueprints espoused by founders in creating new enterprises. We find that those models and the social composition of the labor force at the time of founding had enduring effects on growth in managerial intensity (i.e., reliance on managerial and administrative specialists) over time. Our analyses thus provide compelling evidence of path dependence in the evolution of bureaucracy—even in a context in which firms face intense selection pressures—and underscore the importance of the logics of organizing that founders bring to new enterprises. We find less evidence that founding models exert persistent effects on the formalization of employment relations or on the proliferation of specialized senior management titles. Rather, consistent with neo-institutional perspectives on organizations, those superficial facets of bureaucracy appear to be shaped by the need to satisfy external gatekeepers (venture capitalists and the constituents of public corporations), as well as by exigencies of organizational scale, growth, and aging. We discuss some implications of these results for efforts to understand the varieties, determinants, and consequences of bureaucracy

Inertia and Change in the Early Years: Employment Relations in Young, High Technology Firms

[Excerpt] This paper considers processes of organizational imprinting in a sample of 100 young, high technology companies. It examines the effects of a pair of initial conditions: the founders\u27 models of the employment relation and their business strategies. Our analyses indicate that these two features were well aligned when the firms were founded. However, the alignment has deteriorated over time, due to changes in the distribution of employment models. In particular, the \u27star\u27 model and \u27commitment\u27 model are less stable than the \u27engineering\u27 model and the \u27factory\u27 model. Despite their instability, these two blueprints for the employment relation have strong effects in shaping the early evolution of these firms. In particular, firms that embark with these models have significantly higher rates of replacing the founder chief executive with a non-founder as well as higher rates of completing an initial public stock offering. Some implications of these findings for future studies of imprinting and inertia in organizations are discussed

Determinants of Managerial Intensity in the Early Years of Organizations

This paper examines how founding conditions shape subsequent organizational evolution— specifically, the proliferation of management and administrative jobs. Analyzing quantitative and qualitative information on a sample of young technology start-ups in California’s Silicon Valley, we examine the enduring imprint of two aspects of firms’ founding conditions: the employment blueprints espoused by founders in creating new enterprises; and the social capital that existed among key early members of the firm—their social composition and social relations. We find that the initial gender mix in start-ups and the blueprint espoused by the founder influence the extent of managerial intensity that develops over time. In particular, firms whose founders espoused a bureaucratic model from the outset subsequently grew more administratively intense than otherwise-similar companies, particularly companies whose founders had initially championed a “commitment” model. Also, firms with a higher representation of women within the first year subsequently were slower to bureaucratize than otherwise-similar firms with a predominance of males. Our analyses thus provide compelling evidence of path-dependence in the evolution of organizational structures and underscore the importance of the “logics of organizing” that founders bring to new enterprises. Implications of these results for organizational theory and research are discussed