10,219 research outputs found
Beta Irradiation of a Geometrically Metastable Superconducting Strip Detector with a Magnetic Flux Penetration Read-Out
Geometrical metastability, observed in superconducting type I tin flat
strips, has been previously proposed as a principle for particle detection. The
energy deposition of an incoming beta-particle induces the rupture of the
metastability and consequently the penetration of multiquantum flux tubes into
a superconducting tin strip. We present here the first absorption spectra from
two beta sources, which demonstrate the linearity and energy-resolution of
these detectors (presented at the 6th International Workshop on Low Temperature
Detectors for Dark Matter and Neutrinos (LTD-6), Interlaken, Switzerland, Sept.
1995)Comment: Compressed PostScript (filename.ps.Z), 8 pages, 2 figure
On Context Semantics and Interaction Nets
International audienceContext semantics is a tool inspired by Girard' s geometry of interaction. It has had many applications from study of optimal reduction to proofs of complexity bounds. Yet, context semantics have been defined only on -calculus and linear logic. In order to study other languages, in particular languages with more primitives (built-in arithmetic, pattern matching,...) we define a context semantics for a broader framework: interaction nets. These are a well-behaved class of graph rewriting systems. Here, two applications are explored. First, we define a notion of weight, based on context semantics paths, which bounds the length of reduction of nets. Then, we define a denotational semantics for a large class of interaction net systems
A search for passive protoplanetary disks in the Taurus-Auriga star-forming region
We conducted a 12-month monitoring campaign of 33 T Tauri stars (TTS) in
Taurus. Our goal was to monitor objects that possess a disk but have a weak
Halpha line, a common accretion tracer for young stars, to determine whether
they host a passive circumstellar disk. We used medium-resolution optical
spectroscopy to assess the objects' accretion status and to measure the Halpha
line. We found no convincing example of passive disks; only transition disk and
debris disk systems in our sample are non-accreting. Among accretors, we find
no example of flickering accretion, leading to an upper limit of 2.2% on the
duty cycle of accretion gaps assuming that all accreting TTS experience such
events. Combining literature results with our observations, we find that the
reliability of traditional Halpha-based criteria to test for accretion is high
but imperfect, particularly for low-mass TTS. We find a significant correlation
between stellar mass and the full width at 10 per cent of the peak (W10%) of
the Halpha line that does not seem to be related to variations in free-fall
velocity. Finally, our data reveal a positive correlation between the Halpha
equivalent width and its W10%, indicative of a systematic modulation in the
line profile whereby the high-velocity wings of the line are proportionally
more enhanced than its core when the line luminosity increases. We argue that
this supports the hypothesis that the mass accretion rate on the central star
is correlated with the Halpha W10% through a common physical mechanism.Comment: accepted for publication in MNRAS; 26 pages, 9 figures, 3 table
Lazy Abstraction-Based Controller Synthesis
We present lazy abstraction-based controller synthesis (ABCS) for
continuous-time nonlinear dynamical systems against reach-avoid and safety
specifications. State-of-the-art multi-layered ABCS pre-computes multiple
finite-state abstractions of varying granularity and applies reactive synthesis
to the coarsest abstraction whenever feasible, but adaptively considers finer
abstractions when necessary. Lazy ABCS improves this technique by constructing
abstractions on demand. Our insight is that the abstract transition relation
only needs to be locally computed for a small set of frontier states at the
precision currently required by the synthesis algorithm. We show that lazy ABCS
can significantly outperform previous multi-layered ABCS algorithms: on
standard benchmarks, lazy ABCS is more than 4 times faster
A mid year comparison study of career satisfaction and emotional states between residents and faculty at one academic medical center
BACKGROUND: The Accreditation Council for Graduate Medical Education's (ACGME) new requirements raise multiple challenges for academic medical centers. We sought to evaluate career satisfaction, emotional states, positive and negative experiences, work hours and sleep among residents and faculty simultaneously in one academic medical center after implementation of the ACGME duty hour requirements. METHODS: Residents and faculty (1330) in the academic health center were asked to participate in a confidential survey; 72% of the residents and 66% of the faculty completed the survey. RESULTS: Compared to residents, faculty had higher levels of satisfaction with career choice, competence, importance and usefulness; lower levels of anxiousness and depression. The most positive experiences for both groups corresponded to strong interpersonal relationships and educational value; most negative experiences to poor interpersonal relationships and issues perceived outside of the physician's control. Approximately 13% of the residents and 14% of the faculty were out of compliance with duty hour requirements. Nearly 5% of faculty reported working more than 100 hours per week. For faculty who worked 24 hour shifts, nearly 60% were out of compliance with the duty-hour requirements. CONCLUSION: Reasons for increased satisfaction with career choice, positive emotional states and experiences for faculty compared to residents are unexplained. Earlier studies from this institution identified similar positive findings among advanced residents compared to more junior residents. Faculty are more frequently at risk for duty-hour violations. If patient safety is of prime importance, faculty, in particular, should be compliant with the duty hour requirements. Perhaps the ACGME should contain faculty work hours as part of its regulatory function
S-35 Beta Irradiation of a Tin Strip in a State of Superconducting Geometrical Metastability
We report the first energy loss spectrum obtained with a geometrically
metastable type I superconducting tin strip irradiated by the beta-emission of
S-35. (Nucl. Instr. Meth. A, in press)Comment: Compressed PostScript (filename.ps.Z), 9 pages, 2 figure
What are our Values Worth?
Entrevista a René Girard realizada en 2002 por La Croix sobre los valores, su presencia en distintas obras literarias, la irrupción del terrorismo y las dificultades que enfrentan las sociedades democráticas.post-print3 p
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