1,483 research outputs found
Architects of time: Labouring on digital futures
Drawing on critical analyses of the internet inspired by Gilles Deleuze and the Marxist autonomia movement, this paper suggests a way of understanding the impact of the internet and digital culture on identity and social forms through a consideration of the relationship between controls exercised through the internet, new subjectivities constituted through its use and new labour practices enabled by it. Following Castells, we can see that the distinction between user, consumer and producer is becoming blurred and free labour is being provided by users to corporations. The relationship between digital technologies and sense of community, through their relationship to the future, is considered for its dangers and potentials. It is proposed that the internet may be a useful tool for highlighting and enabling social connections if certain dangers can be traversed. Notably, current remedies for the lack of trust on the internet are questioned with an alternative, drawing on Zygmunt Bauman and Georg Simmel, proposed which is built on community through a vision of a ‘shared network’
Investigation of HV/HR-CMOS technology for the ATLAS Phase-II Strip Tracker Upgrade
ATLAS has formed strip CMOS project to study the use of CMOS MAPS devices as silicon strip sensors for the Phase-II Strip Tracker Upgrade. This choice of sensors promises several advantages over the conventional baseline design, such as better resolution, less material in the tracking volume, and faster construction speed. At the same time, many design features of the sensors are driven by the requirement of minimizing the impact on the rest of the detector. Hence the target devices feature long pixels which are grouped to form a virtual strip with binary-encoded z position. The key performance aspects are radiation hardness compatibility with HL-LHC environment, as well as extraction of the full hit position with full-reticle readout architecture. To date, several test chips have been submitted using two different CMOS technologies. The AMS 350 nm is a high voltage CMOS process (HV-CMOS), that features the sensor bias of up to 120 V. The TowerJazz 180 nm high resistivity CMOS process (HR-CMOS) uses a high resistivity epitaxial layer to provide the depletion region on top of the substrate. We have evaluated passive pixel performance, and charge collection projections. The results strongly support the radiation tolerance of these devices to radiation dose of the HL-LHC in the strip tracker region. We also describe design features for the next chip submission that are motivated by our technology evaluation
Myers' type theorems and some related oscillation results
In this paper we study the behavior of solutions of a second order
differential equation. The existence of a zero and its localization allow us to
get some compactness results. In particular we obtain a Myers' type theorem
even in the presence of an amount of negative curvature. The technique we use
also applies to the study of spectral properties of Schroedinger operators on
complete manifolds.Comment: 16 page
Accreting neutron star spins and the equation of state
X-ray timing of neutron stars in low-mass X-ray binaries (LMXBs) with RXTE
has since 1996 revealed several distinct high-frequency phenomena. Among these
are oscillations during thermonuclear (type-I) bursts, which (in addition to
persistent X-ray pulsations) are thought to trace the neutron star spin. Recent
discoveries bring the total number of measured LMXB spin rates to 22. An open
question is why the majority of the ~100 known neutron stars in LMXBs show
neither pulsations nor burst oscillations.
Recent observations suggest that persistent pulsations may be more common
than previously thought, although detectable intermittently, and in some cases
at very low duty cycles. For example, the 377.3 Hz pulsations in HETE
J1900.1-2455 were only present in the first few months of it's outburst, and
have been absent since (although X-ray activity continues). Intermittent
(persistent) pulsations have since been detected in a further two sources. In
two of these three systems the pulsations appear to be related to the
thermonuclear burst activity, but in the third (Aql X-1) they are not. This
phenomenon offers new opportunities for spin measurements in known systems.
Such measurements can constrain the poorly-known neutron star equation of
state, and neutron stars in LMXBs offer observational advantages over
rotation-powered pulsars which make the detection of more rapidly-spinning
examples more likely. Even so, spin rates of at least 50% faster than the
present maximum appear necessary to give constraints stringent enough to
discriminate between the various models. Although the future prospects for such
rapidly-spinning objects do not appear optimistic, several additional
observational approaches are possible for LMXBs.Comment: 9 pages, 3 figures, includes tables of confirmed rapidly-rotating
accreting neutron stars (as of 2007 Nov. 7). Submitted to the proceedings of
the "40 Years of Pulsars: Millisecond Pulsars, Magnetars and More"
conference, Montreal, August 200
Robust inference of neutron-star parameters from thermonuclear burst observations
Thermonuclear (type-I) bursts arise from unstable ignition of accumulated
fuel on the surface of neutron stars in low-mass X-ray binaries. Measurements
of burst properties in principle enable observers to infer the properties of
the host neutron star and mass donors, but a number of confounding
astrophysical effects contribute to systematic uncertainties. Here we describe
some commonly-used approaches for determining system parameters, including
composition of the burst fuel, and introduce a new suite of software tools,
concord, intended to fully account for astrophysical uncertainties. Comparison
of observed burst properties with the predictions of numerical models is a
complementary method of constraining host properties, and the tools presented
here are intended to make comprehensive model-observation comparisons
straightforward. When combined with the extensive samples of burst observations
accumulated by X-ray observatories, these software tools will provide a
step-change in the amount of information that can be inferred about typical
burst sources.Comment: 22 pages, 11 figures, 1 table & 1 machine-readable table as
supplementary data; submitted to ApJS. Accompanying software package
available at https://github.com/outs1der/concor
Recent Technological Developments on LGAD and iLGAD Detectors for Tracking and Timing Applications
This paper reports the last technological development on the Low Gain
Avalanche Detector (LGAD) and introduces a new architecture of these detectors
called inverse-LGAD (iLGAD). Both approaches are based on the standard
Avalanche Photo Diodes (APD) concept, commonly used in optical and X-ray
detection applications, including an internal multiplication of the charge
generated by radiation. The multiplication is inherent to the basic n++-p+-p
structure, where the doping profile of the p+ layer is optimized to achieve
high field and high impact ionization at the junction. The LGAD structures are
optimized for applications such as tracking or timing detectors for high energy
physics experiments or medical applications where time resolution lower than 30
ps is required. Detailed TCAD device simulations together with the electrical
and charge collection measurements are presented through this work.Comment: Keywords: silicon detectors, avalanche multiplication, timing
detectors, tracking detectors. 8 pages. 8 Figure
Comparison of 35 and 50 {\mu}m thin HPK UFSD after neutron irradiation up to 6*10^15 neq/cm^2
We report results from the testing of 35 {\mu}m thick Ultra-Fast Silicon
Detectors (UFSD produced by Hamamatsu Photonics (HPK), Japan and the comparison
of these new results to data reported before on 50 {\mu}m thick UFSD produced
by HPK. The 35 {\mu}m thick sensors were irradiated with neutrons to fluences
of 0, 1*10^14, 1*10^15, 3*10^15, 6*10^15 neq/cm^2. The sensors were tested
pre-irradiation and post-irradiation with minimum ionizing particles (MIPs)
from a 90Sr \b{eta}-source. The leakage current, capacitance, internal gain and
the timing resolution were measured as a function of bias voltage at -20C and
-27C. The timing resolution was extracted from the time difference with a
second calibrated UFSD in coincidence, using the constant fraction method for
both. Within the fluence range measured, the advantage of the 35 {\mu}m thick
UFSD in timing accuracy, bias voltage and power can be established.Comment: 9 pages, 9 figures, HSTD11 Okinawa. arXiv admin note: text overlap
with arXiv:1707.0496
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