Recursively invoking Linnaeus: A Taxonomy for Naming Systems

Naming is a central element of a distributed or network system design. Appropriate design choices are central. This paper explores a taxonomy of naming systems, and engineering tradeoffs as an aid to the namespace designer. The three orthogonal components of the taxonomy are the characteristics of the namespace itself, name assignment, and name resolution. Within each of these, we explore a number of distinct characteristics. The position of this paper is that engineering design of naming systems should be informed by the possibilities and tradeoffs that those possibilities represent. The paper includes a review of a sampling of naming system designs that reflect different choices within the taxonomy and discussion about why those choices were made.This effort was sponsored by the Defense Advanced Research Projects Agency (DARPA) and Air Force Research Laboratory, Air Force Materiel Command, USAF, under agreement number F30602-00-2-0553

Design Issues in Internet 0 Federation

Internet 0 is proposed as a local area network that supports extremely small network devices with very little capacity for computation, storage, or communication. Internet 0 addresses the issue of connecting very small, inexpensive devices such as lightbulbs and heating vents with their controllers. To achieve this effectively, Internet 0 assumes both that operating between communicating end-nodes should not require third-party support, and that IP will be available all the way to those end-nodes. Several simplifying assumptions are made in Internet 0 to achieve this. The objective of this paper is to explore issues of design in a context where federation of an Internet 0 net either with other Internet 0 nets or the global Internet becomes important. The question we ask is whether the end-node in such an Internet 0 needs to know more or behave differently in such a federated environment, and how one might achieve such federation. We explore three aspects of network design in this study: addressing and routing, traffic collision and congestion control, and security. In each case, based on analysis, we conclude that to reach our goals in a generalizable and extensible fashion, a third party service will be needed to act as an intermediary, and propose that a single service should provide all the required federation services.Singapore-MIT Alliance (SMA

The Molecular Accretion Flow in G10.6-0.4

We have observed the ultracompact HII region G10.6-0.4 with the VLA in 23 GHz continuum and the NH3(3,3) inversion line. By analyzing the optical depth of the line as well as the kinematics, we have detected a flattened, rotating, molecular accretion flow. We detect the fact that the highest column density gas is more flattened, that is, distributed more narrowly, than the lower column density gas, and that there is some inclination of the rotation axis. The rotation is sub-Keplerian, and the molecular gas is not in a rotationally supported disk. We do not find a single massive (proto)star forming in a scaled up version of low mass star formation. Instead, our observations suggest a different mode of clustered massive star formation, in which the accretion flow flattens but does not form an accretion disk. Also in this mode of star formation the central object can be a group of massive stars rather than a single massive star.Comment: 20 pages, 6 figures Accepted for publication in the Astrophysical Journa

Big Data Privacy Scenarios

This paper is the first in a series on privacy in Big Data. As an outgrowth of a series of workshops on the topic, the Big Data Privacy Working Group undertook a study of a series of use scenarios to highlight the challenges to privacy that arise in the Big Data arena. This is a report on those scenarios. The deeper question explored by this exercise is what is distinctive about privacy in the context of Big Data. In addition, we discuss an initial list of issues for privacy that derive specifically from the nature of Big Data. These derive from observations across the real world scenarios and use cases explored in this project as well as wider reading and discussions:* Scale: The sheer size of the datasets leads to challenges in creating, managing and applying privacy policies.* Diversity: The increased likelihood of more and more diverse participants in Big Data collection, management, and use, leads to differing agendas and objectives. By nature, this is likely to lead to contradictory agendas and objectives.* Integration: With increased data management technologies (e.g. cloud services, data lakes, and so forth), integration across datasets, with new and often surprising opportunities for cross-product inferences, will also come new information about individuals and their behaviors.* Impact on secondary participants: Because many pieces of information are reflective of not only the targeted subject, but secondary, often unattended, participants, the inferences and resulting information will increasingly be reflective of other people, not originally considered as the subject of privacy concerns and approaches.* Need for emergent policies for emergent information: As inferences over merged data sets occur, emergent information or understanding will occur. Although each unique data set may have existing privacy policies and enforcement mechanisms, it is not clear that it is possible to develop the requisite and appropriate emerged privacy policies and appropriate enforcement of them automatically

The Extremely High-Velocity Outflow from the Luminous Young Stellar Object G5.89-0.39

We have imaged the extremely high-velocity outflowing gas in CO (2-1) and (3-2) associated with the shell-like ultracompact HII region G5.89-0.39 at a resolution of ~3" (corresponding to ~4000 AU) with the Submillimeter Array. The integrated high-velocity (>45 km/s) CO emission reveals at least three blueshifted lobes and two redshifted lobes. These lobes belong to two outflows, one oriented N-S, the other NW-SE. The NW-SE outflow is likely identical to the previously detected Br_gamma outflow. Furthermore, these outflow lobes all clearly show a Hubble-like kinematic structure. For the first time, we estimate the temperature of the outflowing gas as a function of velocity with the large velocity gradient calculations. Our results reveal a clear increasing trend of temperature with gas velocity. The observational features of the extremely high-velocity gas associated with G5.89-0.39 qualitatively favor the jet-driven bow shock model.Comment: 14 pages, 4 figures, accepted for publication in ApJ Letter

Predictors of presence in virtual reality

The subjective experience of presence is considered to be important in the treatment of anxiety disorders using virtual reality. Presence can be defined as a psychological phenomenon through which one\u27s cognitive processes are oriented towards another world. Most of the research on presence has focused on the roles of technological factors influencing presence, while the number of studies focusing on the personality and physiological predictors are far fewer. Thus, the present study examined the relationship between various personality variables and presence, along with physiological correlates of presence when engaged in a virtual environment. The Presence Questionnaire, to determine their experience of presence, and a small battery of personality-related questionnaires were administered to 70 young adults who participated in 3 different virtual reality scenarios. Participants\u27 physiological responses were recorded in the form of heart rate, galvanic skin levels, and galvanic skin responses were assessed as were urges to drink (craving). Data analysis showed that expectations, levels of craving, and drinking history played a significant role in the experience of presence

High Resolution CO Observations of Massive Star Forming Regions

Context. To further understand the processes involved in the formation of massive stars, we have undertaken a study of the gas dynamics surrounding three massive star forming regions. By observing the large scale structures at high resolution, we are able to determine properties such as driving source, and spatially resolve the bulk dynamical properties of the gas such as infall and outflow. Aims. With high resolution observations, we are able to determine which of the cores in a cluster forming massive stars is responsible for the large scale structures. Methods. We present CO observations of three massive star forming regions with known HII regions and show how the CO traces both infall and outflow. By combining data taken in two SMA configurations with JCMT observations, we are able to see large scale structures at high resolution. Results. We find large (0.26-0.40 pc), massive (2-3 M_sun) and energetic (13-17 \times 10^44 erg) outflows emanating from the edges of two HII regions suggesting they are being powered by the protostar(s) within. We find infall signatures in two of our sources with mass infall rates of order 10-4 M_sun/yr. Conclusions. We suggest that star formation is ongoing in these sources despite the presence of HII regions. We further conclude that the source(s) within a single HII region are responsible for the observed large scale structures; that these large structures are not the net effect of multiple outflows from multiple HII regions and hot cores.Comment: 8 pages,2 figures, accepted for publication in A&

High Velocity Molecular Outflows In Massive Cluster Forming Region G10.6-0.4

We report the arcsecond resolution SMA observations of the $^{12}$CO (2-1) transition in the massive cluster forming region G10.6-0.4. In these observations, the high velocity $^{12}$CO emission is resolved into individual outflow systems, which have a typical size scale of a few arcseconds. These molecular outflows are energetic, and are interacting with the ambient molecular gas. By inspecting the shock signatures traced by CH$_{3}$OH, SiO, and HCN emissions, we suggest that abundant star formation activities are distributed over the entire 0.5 pc scale dense molecular envelope. The star formation efficiency over one global free-fall timescale (of the 0.5 pc molecular envelope, $\sim10^{5}$ years) is about a few percent. The total energy feedback of these high velocity outflows is higher than 10$^{47}$ erg, which is comparable to the total kinetic energy in the rotational motion of the dense molecular envelope. From order-of-magnitude estimations, we suggest that the energy injected from the protostellar outflows is capable of balancing the turbulent energy dissipation. No high velocity bipolar molecular outflow associated with the central OB cluster is directly detected, which can be due to the photo-ionization.Comment: 42 pages, 14 figures, accepted by Ap

Experimental Observation Of Correlated Magnetic Reconnection And Alfvénic Ion Jets

Correlations between magnetic reconnection and energetic ion flow events have been measured with merging force free spheromaks at the Swarthmore Spheromak Experiment. The reconnection layer is measured with a linear probe array and ion flow is directly measured with a retarding grid energy analyzer. Flow has been measured both in the plane of the reconnection layer and out of the plane. The most energetic events occur in the reconnection plane immediately after formation as the spheromaks dynamically merge. The outflow velocity is nearly Alfvenic. As the spheromaks form equilibria and decay, the flow is substantially reduced

The Origin of OB Clusters: From 10 pc to 0.1 pc

We observe the 1.2 mm continuum emission around the OB cluster forming region G10.6-0.4, using the IRAM 30m telescope MAMBO-2 bolometer array and the Submillimeter array. Comparison of the Spitzer 24 $\mu$m and 8 $\mu$m images with our 1.2 mm continuum maps reveals the ionization front of an HII region, the photon-dominated layer, and several 5 pc scale filaments following the outer edge of the photon-dominated layer. The filaments, which are resolved in the MAMBO-2 observations, show regularly spaced parsec-scale molecular clumps, embedded with a cluster of submillimeter molecular cores as shown in the SMA 0.87 mm observations. Toward the center of the G10.6-0.4 region, the combined SMA+IRAM 30m continuum image reveals several, parsec-scale protrusions. They may continue down to within 0.1 pc of the geometric center of a dense 3 pc size structure, where a 200 M$_{\odot}$ OB cluster resides. The observed filaments may facilitate mass accretion onto the central cluster--forming region in the presence of strong radiative and mechanical stellar feedbacks. Their filamentary geometry may also facilitate fragmentation. We did not detect any significant polarized emission at 0.87 mm in the inner 1 pc region with the SMA.Comment: 32 pages, 10 figures, Accepted by ApJ on 2011.October