3,223 research outputs found
Generalized Kuhn-Tucker Conditions for N-Firm Stochastic Irreversible Investment under Limited Resources
In this paper we study a continuous time, optimal stochastic investment
problem under limited resources in a market with N firms. The investment
processes are subject to a time-dependent stochastic constraint. Rather than
using a dynamic programming approach, we exploit the concavity of the profit
functional to derive some necessary and sufficient first order conditions for
the corresponding Social Planner optimal policy. Our conditions are a
stochastic infinite-dimensional generalization of the Kuhn-Tucker Theorem. The
Lagrange multiplier takes the form of a nonnegative optional random measure on
[0,T] which is flat off the set of times for which the constraint is binding,
i.e. when all the fuel is spent. As a subproduct we obtain an enlightening
interpretation of the first order conditions for a single firm in Bank (2005).
In the infinite-horizon case, with operating profit functions of Cobb-Douglas
type, our method allows the explicit calculation of the optimal policy in terms
of the `base capacity' process, i.e. the unique solution of the Bank and El
Karoui representation problem (2004).Comment: 25 page
Salvage of Exposed Breast Implant Using Capsular Flaps
Objective: Extrusion represents potential complications associated with the use of breast implants. Attempts to salvage the exposed implants are rarely successful when poor tissue coverage or radiotherpy is present and therefore removal of implant and wound healing are mandatory. In these refractory complicated cases the use of capsular flaps can represent a useful tool to save the implant and achieve definitive healing. Methods: Capsular flaps have been performed on 6 patients with implant extrusion and 11 patients with breast contour deformities over the last 6 years. The authors describe an innovative technique using capsular flaps which are harvested from thicker viable tissues and inset in multiple layers into the fistula tract to reinforce the breast envelope and prevent recurrence of implant extrusion. Results: Complete healing and implant salvage were achieved in all patients treated. No major complications occurred and only minor contour deformities, that regressed spontaneously after surgery, were observed for 2 weeks. Conclusions: Although capsular flaps have been previously described to correct breast shape deformities, no previous report has yet suggested its utility in breast implant salvage in case of extrusion. The authors advocate the use of capsular flap to save the exposed breast implant especially when poor tissue coverage is present and other surgical options to save the implant have already failed
Plans for a 10-m Submillimeter-wave Telescope at the South Pole
A 10 meter diameter submillimeter-wave telescope has been proposed for the
NSF Amundsen-Scott South Pole Station. Current evidence indicates that the
South Pole is the best submillimeter-wave telescope site among all existing or
proposed ground-based observatories. Proposed scientific programs place
stringent requirements on the optical quality of the telescope design. In
particular, reduction of the thermal background and offsets requires an
off-axis, unblocked aperture, and the large field of view needed for survey
observations requires shaped optics. This mix of design elements is well-suited
for large scale (square degree) mapping of line and continuum radiation from
submillimeter-wave sources at moderate spatial resolutions (4 to 60 arcsecond
beam size) and high sensitivity (milliJansky flux density levels). the
telescope will make arcminute angular scale, high frequency Cosmic Microwave
Background measurements from the best possible ground-based site, using an
aperture which is larger than is currently possible on orbital or airborne
platforms. Effective use of this telescope will require development of large
(1000 element) arrays of submillimeter detectors which are background-limited
when illuminated by antenna temperatures near 50 K.Comment: 12 pages, 3 figure
P2-328: Is pemetrexed more effective in adenocarcinoma and large cell lung cancer than in squamous cell carcinoma? A retrospective analysis of a phase III trial of pemetrexed vs docetaxel in previously treated patients with advanced non-small cell lung cancer (NSCLC)
I.C.E.: a Transportable Atomic Inertial Sensor for Test in Microgravity
We present our the construction of an atom interferometer for inertial
sensing in microgravity, as part of the I.C.E. (\textit{Interf\'{e}rom\'{e}trie
Coh\'{e}rente pour l'Espace}) collaboration. On-board laser systems have been
developed based on fibre-optic components, which are insensitive to mechanical
vibrations and acoustic noise, have sub-MHz linewidth, and remain frequency
stabilised for weeks at a time. A compact, transportable vacuum system has been
built, and used for laser cooling and magneto-optical trapping. We will use a
mixture of quantum degenerate gases, bosonic Rb and fermionic K,
in order to find the optimal conditions for precision and sensitivity of
inertial measurements. Microgravity will be realised in parabolic flights
lasting up to 20s in an Airbus. We show that the factors limiting the
sensitivity of a long-interrogation-time atomic inertial sensor are the phase
noise in reference frequency generation for Raman-pulse atomic beam-splitters
and acceleration fluctuations during free fall
Resource-Bound Quantification for Graph Transformation
Graph transformation has been used to model concurrent systems in software
engineering, as well as in biochemistry and life sciences. The application of a
transformation rule can be characterised algebraically as construction of a
double-pushout (DPO) diagram in the category of graphs. We show how
intuitionistic linear logic can be extended with resource-bound quantification,
allowing for an implicit handling of the DPO conditions, and how resource logic
can be used to reason about graph transformation systems
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