217 research outputs found
Monte Carlo methods for pricing and hedging American options
We introduce a new Monte Carlo method for constructing the exercise boundary of an American option in a generalized Black-Scholes framework. Based on a known exercise boundary, it is shown how to price and hedge the American option by Monte Carlo simulation of suitable probabilistic representations in connection with the respective parabolic boundary value problem. The methods presented are supported by numerical simulation experiments
Breaking with Fixed Set Pathology Recognition through Report-Guided Contrastive Training
When reading images, radiologists generate text reports describing the findings therein. Current state-of-the-art computer-aided diagnosis tools utilize a fixed set of predefined categories automatically extracted from these medical reports for training. This form of supervision limits the potential usage of models as they are unable to pick up on anomalies outside of their predefined set, thus, making it a necessity to retrain the classifier with additional data when faced with novel classes. In contrast, we investigate direct text supervision to break away from this closed set assumption. By doing so, we avoid noisy label extraction via text classifiers and incorporate more contextual information. We employ a contrastive global-local dual-encoder architecture to learn concepts directly from unstructured medical reports while maintaining its ability to perform free form classification. We investigate relevant properties of open set recognition for radiological data and propose a method to employ currently weakly annotated data into training. We evaluate our approach on the large-scale chest X-Ray datasets MIMIC-CXR, CheXpert, and ChestX-Ray14 for disease classification. We show that despite using unstructured medical report supervision, we perform on par with direct label supervision through a sophisticated inference setting
Breaking with Fixed Set Pathology Recognition through Report-Guided Contrastive Training
When reading images, radiologists generate text reports describing the
findings therein. Current state-of-the-art computer-aided diagnosis tools
utilize a fixed set of predefined categories automatically extracted from these
medical reports for training. This form of supervision limits the potential
usage of models as they are unable to pick up on anomalies outside of their
predefined set, thus, making it a necessity to retrain the classifier with
additional data when faced with novel classes. In contrast, we investigate
direct text supervision to break away from this closed set assumption. By doing
so, we avoid noisy label extraction via text classifiers and incorporate more
contextual information.
We employ a contrastive global-local dual-encoder architecture to learn
concepts directly from unstructured medical reports while maintaining its
ability to perform free form classification.
We investigate relevant properties of open set recognition for radiological
data and propose a method to employ currently weakly annotated data into
training.
We evaluate our approach on the large-scale chest X-Ray datasets MIMIC-CXR,
CheXpert, and ChestX-Ray14 for disease classification. We show that despite
using unstructured medical report supervision, we perform on par with direct
label supervision through a sophisticated inference setting.Comment: Provisionally Accepted at MICCAI202
Raman cooling and heating of two trapped Ba+ ions
We study cooling of the collective vibrational motion of two 138Ba+ ions
confined in an electrodynamic trap and irradiated with laser light close to the
resonances S_1/2-P_1/2 (493 nm) and P_1/2-D_3/2 (650 nm). The motional state of
the ions is monitored by a spatially resolving photo multiplier. Depending on
detuning and intensity of the cooling lasers, macroscopically different
motional states corresponding to different ion temperatures are observed. We
also derive the ions' temperature from detailed analytical calculations of
laser cooling taking into account the Zeeman structure of the energy levels
involved. The observed motional states perfectly match the calculated
temperatures. Significant heating is observed in the vicinity of the dark
resonances of the Zeeman-split S_1/2-D_3/2 Raman transitions. Here two-photon
processes dominate the interaction between lasers and ions. Parameter regimes
of laser light are identified that imply most efficient laser cooling.Comment: 8 pages, 5 figure
-Photoproduction on the deuteron via -excitation using the Lorentz Integral Transform
The Lorentz Integral Transform method (LIT) is extended to pion
photoproduction in the -resonance region. The main focus lies on the
solution of the conceptual difficulties which arise if energy dependent
operators for nucleon resonance excitations are considered. In order to
demonstrate the applicability of our approach, we calculate the inclusive cross
section for -photoproduction off the deuteron within a simple pure
resonance model.Comment: 4 pages, EPJA styl
Degradation Kinetics of Lignocellulolytic Enzymes in a Biogas Reactor Using Quantitative Mass Spectrometry
The supplementation of lignocellulose-degrading enzymes can be used to enhance the performance of biogas production in industrial biogas plants. Since the structural stability of these enzyme preparations is essential for efficient application, reliable methods for the assessment of enzyme stability are crucial. Here, a mass-spectrometric-based assay was established to monitor the structural stability of enzymes, i.e., the structural integrity of these proteins, in anaerobic digestion (AD). The analysis of extracts of Lentinula edodes revealed the rapid degradation of lignocellulose-degrading enzymes, with an approximate half-life of 1.5 h. The observed low structural stability of lignocellulose-degrading enzymes in AD corresponded with previous results obtained for biogas content. The established workflow can be easily adapted for the monitoring of other enzyme formulations and provides a platform for evaluating the effects of enzyme additions in AD, together with a characterization of the biochemical methane potential used in order to determine the biodegradability of organic substrates
Asymptotic equivalence of discretely observed diffusion processes and their Euler scheme: small variance case
This paper establishes the global asymptotic equivalence, in the sense of the
Le Cam -distance, between scalar diffusion models with unknown drift
function and small variance on the one side, and nonparametric autoregressive
models on the other side. The time horizon is kept fixed and both the cases
of discrete and continuous observation of the path are treated. We allow non
constant diffusion coefficient, bounded but possibly tending to zero. The
asymptotic equivalences are established by constructing explicit equivalence
mappings.Comment: 21 page
- …