Clustering in ICT: From Route 128 to Silicon Valley, from DEC to Google, from Hardware to Content

One of the pioneers in academic entrepreneurship and high-tech clustering is MIT and the Route 128/Boston region. Silicon Valley centered around Stanford University was originally a fast follower and only later emerged as a scientific and industrial hotspot. Several technology and innovation waves, have shaped Silicon Valley over all the years. The initial regional success of Silicon Valley started with electro-technical instruments and defense applications in the 1940s and 1950s (represented by companies as Litton Engineering and Hewlett & Packard). In the 1960s and 1970s, the region became a national and international leader in the design and production of integrated circuit and computer chips, and as such became identified as Silicon Valley (e.g. Fairchild Semiconductor, and Intel). In the 1970s and 1980s, Silicon Valley capitalised further on the development, manufacturing and sales of the personal computer and workstations (e.g. Apple, Silicon Graphics and SUN), followed by the proliferation of telecommunications and Internet technologies in the 1990s (e.g. Cisco, 3Com) and Internet-based applications and info-mediation services (e.g. Yahoo, Google) in the late 1990s and early 2000s. When the external and/or internal conditions of its key industries change, Silicon Valley seemed to have an innate capability to restructure itself by a rapid and frequent reshuffling of people, competencies, resources and firms. To characterise the demise of one firm leading, directly or indirectly, to the formation of another and the reconfiguration of business models and product offerings by the larger companies in emerging industries, Bahrami & Evans (2000) introduced the term `flexible recycling.’ This dynamic process of learning by doing, failing and recombining (i.e. allowing new firms to rise from the ashes of failed enterprises) is one of the key factors underlying the dominance of Silicon Valley in the new economy.ICT;Clusters;Networks;Academic entrepreneurship;MIT;Silicon Valley;Stanford University;Flexible recycling;Route 128

High spatial resolution mid-infrared observations of the low-mass young star TW Hya

We want to improve knowledge of the structure of the inner few AU of the circumstellar disk around the nearby T Tauri star TW Hya. Earlier studies have suggested the existence of a large inner hole, possibly caused by interactions with a growing protoplanet. We used interferometric observations in the N-band obtained with the MIDI instrument on the Very Large Telescope Interferometer, together with 10 micron spectra recorded by the infrared satellite Spitzer. The fact that we were able to determine N-band correlated fluxes and visibilities for this comparatively faint source shows that MIR interferometry can be applied to a large number of low-mass young stellar objects. The MIR spectra obtained with Spitzer reveal emission lines from HI (6-5), HI (7-6), and [Ne II] and show that over 90% of the dust we see in this wavelength regime is amorphous. According to the correlated flux measured with MIDI, most of the crystalline material is in the inner, unresolved part of the disk, about 1 AU in radius. The visibilities exclude the existence of a very large (3-4 AU radius) inner hole in the circumstellar disk of TW Hya, which was required in earlier models. We propose instead a geometry of the inner disk where an inner hole still exists, but at a much reduced radius, with the transition from zero to full disk height between 0.5 and 0.8 AU, and with an optically thin distribution of dust inside. Such a model can comply with SED and MIR visibilities, as well as with visibility and extended emission observed in the NIR at 2 micron. If a massive planet was the reason for this inner hole, as has been speculated, its orbit would have to be closer to the star than 0.3 AU. Alternatively, we may be witnessing the end of the accretion phase and an early phase of an inward-out dispersal of the circumstellar disk.Comment: 13 pages, 9 figures, accepted by A&

Young stars in Epsilon Cha and their disks: disk evolution in sparse associations

(abridge) The nearby young stellar association Epsilon Cha association has an estimated age of 3-5 Myr, making it an ideal laboratory to study the disk dissipation process and provide empirical constraints on the timescale of planet formation. We combine the available literature data with our Spitzer IRS spectroscopy and VLT/VISIR imaging data. The very low mass stars USNO-B120144.7 and 2MASS J12005517 show globally depleted spectral energy distributions pointing at strong dust settling. 2MASS J12014343 may have a disk with a very specific inclination where the central star is effectively screened by the cold outer parts of a flared disk but the 10 micron radiation of the warm inner disk can still reach us. We find the disks in sparse stellar associations are dissipated more slowly than those in denser (cluster) environments. We detect C_{2}H_{2} rovibrational band around 13.7 micron on the IRS spectrum of USNO-B120144.7. We find strong signatures of grain growth and crystallization in all Epsilon Cha members with 10 micron features detected in their IRS spectra. We combine the dust properties derived in the Epsilon Cha sample with those found using identical or similar methods in the MBM 12, Coronet cluster, Eta Cha associations, and in the cores to disks (c2d) legacy program. We find that disks around low-mass young stars show a negative radial gradient in the mass-averaged grain size and mass fraction of crystalline silicates. A positive correlation exists between the mass-averaged grain sizes of amorphous silicates and the accretion rates if the latter is above ~10^{-9} Msun/yr, possibly indicating that those disks are sufficiently turbulent to prevent grains of several microns in size to sink into the disk interior.Comment: 17 pages, 18 figures, 6 tables, language revised; accepted to A&

Clustering in ICT: From Route 128 to Silicon Valley, from DEC to Google, from Hardware to Content

One of the pioneers in academic entrepreneurship and high-tech clustering is MIT and the Route 128/Boston region. Silicon Valley centered around Stanford University was originally a fast follower and only later emerged as a scientific and industrial hotspot. Several technology and innovation waves, have shaped Silicon Valley over all the years. The initial regional success of Silicon Valley started with electro-technical instruments and defense applications in the 1940s and 1950s (represented by companies as Litton Engineering and Hewlett & Packard). In the 1960s and 1970s, the region became a national and international leader in the design and production of integrated circuit and computer chips, and as such became identified as Silicon Valley (e.g. Fairchild Semiconductor, and Intel). In the 1970s and 1980s, Silicon Valley capitalised further on the development, manufacturing and sales of the personal computer and workstations (e.g. Apple, Silicon Graphics and SUN), followed by the proliferation of telecommunications and Internet technologies in the 1990s (e.g. Cisco, 3Com) and Internet-based ap

Silicon Valley in the Polder? Entrepreneurial Dynamics, Virtuous Clusters and Vicious Firms in the Netherlands and Flanders

High-technology starters do not operate in a vacuum and innovation is not a solitary activity. The activities of technology-based firms are embedded in socio-economic networks with other companies, investors, universities, vocational institutions, etc. The geographical proximity of those institutions and infrastructural hubs will partly play a role in determine the location of ICT firms decision. Furthermore, many high-tech companies shape clusters around areas where their major customers are located. The topic of this paper is regional clustering Enright, 1992; Rosenfeld, 1997within the context of Internet and ICT technology. A dynamic model previously developed for the analysis of ICT-entrepreneurship and

Concept for a Time-of-Flight Small Angle Neutron Scattering Instrument at the European Spallation Source

A new Small Angle Neutron Scattering instrument is proposed for the European Spallation Source. The pulsed source requires a time-of-flight analysis of the gathered neutrons at the detector. The optimal instrument length is found to be rather large, which allows for a polarizer and a versatile collimation. The polarizer allows for studying magnetic samples and incoherent background subtraction. The wide collimation will host VSANS and SESANS options that increase the resolution of the instrument towards um and tens of um, respectively. Two 1m2 area detectors will cover a large solid angle simultaneously. The expected gains for this new instrument will lie in the range between 20 and 36, depending on the assessment criteria, when compared to up-to-date reactor based instruments. This will open new perspectives for fast kinetics, weakly scattering samples, and multi-dimensional contrast variation studies.Comment: 18 pages, 10 figure

Binarity as a key factor in protoplanetary disk evolution: Spitzer disk census of the eta Chamaeleontis cluster

The formation of planets is directly linked to the evolution of the circumstellar (CS) disk from which they are born. The dissipation timescales of CS disks are, therefore, of direct astrophysical importance in evaluating the time available for planet formation. We employ Spitzer Space Telescope spectra to complete the CS disk census for the late-type members of the ~8 Myr-old eta Chamaeleontis star cluster. Of the 15 K- and M-type members, eight show excess emission. We find that the presence of a CS disk is anti-correlated with binarity, with all but one disk associated with single stars. With nine single stars in total, about 80% retain a CS disk. Of the six known or suspected close binaries the only CS disk is associated with the primary of RECX 9. No circumbinary disks have been detected. We also find that stars with disks are slow rotators with surface values of specific angular momentum j = 2-15 j_sun. All high specific angular momentum systems with j = 20-30 j_sun are confined to the primary stars of binaries. This provides novel empirical evidence for rotational disk locking and again demonstrates the much shorter disk lifetimes in close binary systems compared to single star systems. We estimate the characteristic mean disk dissipation timescale to be ~5 Myr and ~9 Myr for the binary and single star systems, respectively.Comment: Accepted by ApJ

Ecology and cultivation of the herbivorous brackish-water nematode Eudiplogaster pararmatus

The sediment inhabiting rhabditld nematode Eudiplogaster pararmatus (W. Schneider 1938), is a halophilic member of the family Dlplogasteridae (non-marine animals, often occurring in saprobic environments). It colonizes successfully the waste-water exposed intertidal mud flats in the southeast of the Ems-Dollard estuary, The Netherlands. Microscopic observations in agar cultures witness that E. pararmatus feeds on diatoms. The nematode consumed representatives of 7 different diatom species by puncturing their frustules and swallowing their contents. Adults consumed about 7 cells h-' of Navicula saljnarum (Grunow). Comparable consumption rates were calculated from experiments by other researchers, with 14C labelled diatoms. The reproduction and population growth of E. pararmatus were studied in cultures with various salinities and diatom densities at a temperature of 17 'C. Reproduction occurred under almost all conditions but the number of nematodes increased importantly only in cultures with low salinities (0.5 to 2.5 460 S) and food densities of over 2 X 106 cells cm-3. Growth of individual nematodes was studied at 2 different temperatures in agar cultures with low salinities and adequate food. Temperature appeared to govern the moment of sexual differentiation: at 12 "C, this differentiation occurred after approximately 2.5 wk; at 21 "C, after only 1.5 wk. Generation times observed in cultures varied between 45 d (at 12 "C) and 21 d (at 21 'C); this is in the same range as the generation time found for other brackish water and marine nematodes with a similar life style Tentative calculations of the reproductive rate of exponentially growing populations in the field (in spring, 12" to 18 'C), revealed a generation time of 25 to 33 d; this is slightly shorter than the generation time observed in cultures. Brief exposure to high temperatures during emersion of the flats may be responsible for this difference