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Thomas Jansen

Publications and source records attributed to Thomas Jansen.

25 records · Page 2Linked to original sources
PubMed2004

The cooperative coevolutionary (1+1) EA.

Coevolutionary algorithms are variants of traditional evolutionary algorithms and are often considered more suitable for certain kinds of complex tasks than noncoevolutionary methods. One example is a general cooperative coevolutionary framework for function optimization. This paper presents a thorough and rigorous introductory analysis of the optimization potential of cooperative coevolution. Using the cooperative coevolutionary framework as a starting point, the CC (1+1) EA is defined and investigated from the perspective of the expected optimization time. The research concentrates on separability, a key property of objective functions. We show that separability alone is not sufficient to yield any advantage of the CC (1+1) EA over its traditional, non-coevolutionary counterpart. Such an advantage is demonstrated to have its basis in the increased explorative possibilities of the cooperative coevolutionary algorithm. For inseparable functions, the cooperative coevolutionary set-up can be harmful. We prove that for some objective functions the CC (1+1) EA fails to locate a global optimum with overwhelming probability, even in infinite time; however, inseparability alone is not sufficient for an objective function to cause difficulties. It is demonstrated that the CC (1+1) EA may perform equal to its traditional counterpart, and may even outperform it on certain inseparable functions.

Algorithms↗
PubMed2002

Mitochondrial DNA and the origins of the domestic horse.

The place and date of the domestication of the horse has long been a matter for debate among archaeologists. To determine whether horses were domesticated from one or several ancestral horse populations, we sequenced the mitochondrial D-loop for 318 horses from 25 oriental and European breeds, including American mustangs. Adding these sequences to previously published data, the total comes to 652, the largest currently available database. From these sequences, a phylogenetic network was constructed that showed that most of the 93 different mitochondrial (mt)DNA types grouped into 17 distinct phylogenetic clusters. Several of the clusters correspond to breeds and/or geographic areas, notably cluster A2, which is specific to Przewalski's horses, cluster C1, which is distinctive for northern European ponies, and cluster D1, which is well represented in Iberian and northwest African breeds. A consideration of the horse mtDNA mutation rate together with the archaeological timeframe for domestication requires at least 77 successfully breeding mares recruited from the wild. The extensive genetic diversity of these 77 ancestral mares leads us to conclude that several distinct horse populations were involved in the domestication of the horse.

Animals↗
PubMed2002

Low-dose ultraviolet A1 phototherapy for extragenital lichen sclerosus: results of a preliminary study.

BACKGROUND: Lichen sclerosus (LS) is a chronic inflammatory skin disease in which numerous therapies have been used, with only limited success. Because low-dose UVA1 phototherapy has been shown to be an effective treatment option for localized scleroderma, which shares several similar clinical and histologic features with LS, we initiated a clinical trial with this phototherapeutic modality in patients with LS. METHODS: Ten patients suffering from extragenital LS were treated with low-dose UVA1 phototherapy 4 times weekly with single UVA1 doses of 20 J/cm(2). Forty treatment sessions were performed within 10 weeks, resulting in a cumulative UVA1 dose of 800 J/cm(2). RESULTS: Low-dose UVA1 phototherapy resulted in a marked reduction of the clinical score and a significant (P <.05) decrease of ultrasonographically measured skin thickness as well as a highly significant (P <.001) increase of dermal density. The patients reported a remarkable softening and repigmentation of the affected skin. CONCLUSION: Analogous to the treatment results in localized scleroderma, low-dose UVA1 phototherapy seems to be an effective and well-tolerated treatment option for extragenital LS.

Adult↗
PubMedDate not supplied

[Hypofractionated radiation therapy for the treatment of malignant melanoma and squamous cell carcinoma in dogs and cats].

This study describes the experience with hypofractionated radiation therapy of squamous cell carcinoma and melanoma in dogs and cats. A total dose of 32-48 Gray (Gy) was delivered once a week in 8 Gy fractions. 34 animals in which a complete surgical excision was impossible were treated. There was no tumor detectable macroscopically in 14 patients at the beginning of radiation therapy. In 20 animals the median volume of the tumor was 9.9 cm3. The median survival times and the local tumor control of squamous cell carcinoma of the oral and nasal cavities and of the body are comparable to results which were reached with a Monday-Wednesday-Friday scheme. For the treatment of Melanoma the hypofractionated radiation therapy is first choice. There are no significant side effects. Late side effects did not occur. 88% of the owners are satisfied with this kind of treatment and would choose it again.

Animals↗