A Stochastic Model of Cell Cycle Desynchronization

A general branching process model is suggested to describe cell cycle desynchronization. Cell cycle phase times are modeled as random variables and a formula for the expected fraction of cells in S phase as a function of time is established. The model is compared to data from the literature and is also compared to previously suggested deterministic and stochastic models

The twofold debris disk around HD 113766 A - Warm and cold dust as seen with VLTI/Midi and Herschel/Pacs

Warm debris disks are a sub-sample of the large population of debris disks, and display excess emission in the mid-IR. Around solar-type stars, very few objects show emission features in mid-IR spectroscopic observations, that are attributed to small, warm silicate dust grains. The origin of this warm dust can possibly be explained either by a collision between several bodies or by transport from an outer belt. We present and analyse new far-IR Herschel/Pacs observations, supplemented by ground-based data in the mid-IR (VLTI/Midi and VLT/Visir), for one of these rare systems: the 10-16 Myr old debris disk around HD 113766 A. We improve an existing model to account for these new observations, and better constrain the spatial distribution of the dust and its composition. We underline the limitations of SED modelling and the need for spatially resolved observations. We find that the system is best described by an inner disk located within the first AU, well constrained by the Midi data, and an outer disk located between 9-13 AU. In the inner dust belt, our previous finding of Fe-rich crystalline olivine grains still holds. We do not observe time variability of the emission features over at least a 8 years time span, in a environment subjected to strong radiation pressure. The time stability of the emission features indicates that {\mu}m-sized dust grains are constantly replenished from the same reservoir, with a possible depletion of sub-{\mu}m-sized grains. We suggest that the emission features may arise from multi-composition aggregates. We discuss possible scenarios concerning the origin of the warm dust. The compactness of the innermost regions as probed by Midi, as well as the dust composition, suggest that we are witnessing the outcomes of (at least) one collision between partially differentiated bodies, in an environment possibly rendered unstable by terrestrial planetary formation

Collaborative Whiteboard: Towards Remote CollaBoration and Interaction in Construction Design

The need for improved collaboration and interaction in construction projects has grown significantly in recent years, especially as projects have become ever more complex. The early design stage is of particular importance for the final results as most of the building’s lifecycle characteristics are committed at this stage, and the opportunity to influence them decreases rapidly as the cost of making changes, or correcting design errors, increases dramatically. Recent advances in information technology offer methods and tools to meet this need. In view of this, a collaborative whiteboard (CollaBoard) for remote collaboration – is being developed to support mixed, geographically distributed teams. Interconnected via a network, two or more system setups allow users to interact and share information over a common, interactive vertical whiteboard, allowing experts from different disciplines access to databases through intuitive interfaces in order to integrate and optimize lifecycle-related parameters into a new product. Superimposing the live video of the remote partner – “people on content” – also allows the transfer of meta information, such as gestures, resulting in more intuitively distributed collaborative teamwork

RELATIONAL CONTRACTING AND PROCESS DESIGN PROMOTING COOPERATION

ABSTRACT In Sweden as in many other countries new demands have led to the set-up of public committees and research projects for scrutinizing the construction sector. The main conclusions are that traditional models for managing the building process do not match the nature of today's fasttrack, uncertain and complex projects. Since 2004 there is also a government appointed Committee in Sweden dealing with these matters. It is interesting to notice that the Committee has already given prominence to Lean Construction ideas and concepts as a model for the future of the Swedish construction sector. New ideas and innovative concepts for the development of the construction process in huge projects which are extremely quick, uncertain and complex have been tested by the Swedish mining company LKAB at a pelletizing plant project described in this paper. The project is procured as a partnering project on DB (Design and Build) basis and with transparent remuneration form. The expectations and demands from the client concerning targets regarding time, cost and functions are set high. Advanced design models such as 3D, 4D and VR has been used to support a concurrent engineering design and construction process. This paper will mainly deal with the relational contracting aspects. Especially, how the contracting model affects the process design. The results of the study presented are based on a field survey case study carried through by the authors

Herschel Observations of the T Cha Transition Disk: Constraining the Outer Disk Properties

T Cha is a nearby (d similar to 100 pc) transition disk known to have an optically thin gap separating optically thick inner and outer disk components. Huelamo et al. recently reported the presence of a low-mass object candidate within the gap of the T Cha disk, giving credence to the suspected planetary origin of this gap. Here we present the Herschel photometry (70, 160, 250, 350, and 500 mu m) of T Cha from the "Dust, Ice, and Gas in Time" Key Program, which bridges the wavelength range between existing Spitzer and millimeter data and provide important constraints on the outer disk properties of this extraordinary system. We model the entire optical to millimeter wavelength spectral energy distribution (SED) of T Cha (19 data points between 0.36 and 3300 mu m without any major gaps in wavelength coverage). T Cha shows a steep spectral slope in the far-IR, which we find clearly favors models with outer disks containing little or no dust beyond similar to 40 AU. The full SED can be modeled equally well with either an outer disk that is very compact (only a few AU wide) or a much larger one that has a very steep surface density profile. That is, T Cha's outer disk seems to be either very small or very tenuous. Both scenarios suggest a highly unusual outer disk and have important but different implications for the nature of T Cha. Spatially resolved images are needed to distinguish between the two scenarios.DIGIT Herschel Open Time Key ProgramNASAAlexander von Humboldt FoundationEuropean CommissionAgence Nationale pour la Recherche of France PERG06-GA-2009-256513, ANR-07-BLAN-0221, ANR-2010-JCJC-0504-01CNRS/INSU, FranceAstronom

The Herschel Digit Survey Of Weak-Line T Tauri Stars: Implications For Disk Evolution And Dissipation

As part of the "Dust, Ice, and Gas In Time (DIGIT)" Herschel Open Time Key Program, we present Herschel photometry (at 70, 160, 250, 350, and 500 mu m) of 31 weak-line T Tauri star (WTTS) candidates in order to investigate the evolutionary status of their circumstellar disks. Of the stars in our sample, 13 had circumstellar disks previously known from infrared observations at shorter wavelengths, while 18 of them had no previous evidence for a disk. We detect a total of 15 disks as all previously known disks are detected at one or more Herschel wavelengths and two additional disks are identified for the first time. The spectral energy distributions (SEDs) of our targets seem to trace the dissipation of the primordial disk and the transition to the debris disk regime. Of the 15 disks, 7 appear to be optically thick primordial disks, including 2 objects with SEDs indistinguishable from those of typical Classical T Tauri stars, 4 objects that have significant deficit of excess emission at all IR wavelengths, and 1 "pre-transitional" object with a known gap in the disk. Despite their previous WTTS classification, we find that the seven targets in our sample with optically thick disks show evidence for accretion. The remaining eight disks have weaker IR excesses similar to those of optically thin debris disks. Six of them are warm and show significant 24 mu m Spitzer excesses, while the last two are newly identified cold debris-like disks with photospheric 24 mu m fluxes, but significant excess emission at longer wavelengths. The Herschel photometry also places strong constraints on the non-detections, where systems with F-70/F-70,(*) greater than or similar to 5-15 and L-disk/L-* greater than or similar to 10(-3) to 10(-4) can be ruled out. We present preliminary models for both the optically thick and optically thin disks and discuss our results in the context of the evolution and dissipation of circumstellar disks.NASA through JPL/CaltechNASA through the Sagan Fellowship ProgramEuropean Commission PERG06-GA-2009-256513Agence Nationale pour la Recherche (ANR) of France ANR-2010-JCJC-0504-01CFHT 11AH96Astronom