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- Blomqvist, M., et al.
(författare)
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Fundamental-mode fiber-to-fiber coupling at high-power
- 2009
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Ingår i: Solid State Lasers XVIII. - : SPIE - International Society for Optical Engineering. - 9780819474391 ; , s. 71930F-
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Konferensbidrag (refereegranskat)abstract
- Fiber-to-fiber coupling between two different fibers is a state of the art technology. Products are available on the market where multimode fibers can be coupled with very low power loss, at very high powers (multi-kilowatt). We have, however, always been forced to accept a certain loss in beam quality, manifesting as an increase in the Beam Parameter Product (BPP). In fundamental-mode fiber-to-fiber coupling no beam quality is lost. We instead expect to have a certain power loss in the coupling. This paper addresses the problems in free-space fundamental-mode fiber-to-fiber coupling, including theoretical estimations of expected power loss, estimated demands on the stability of the optics as well as measured values on a fundamental mode fiber-to-fiber coupler. The theoretical calculations of the sensitivity of the coupling efficiency due to radial misalignment and defocus (longitudinal displacement) have been confirmed experimentally. Experimental results at 100 W laser power include 88% coupling efficiency using a large mode area fiber with mode-field diameter (MFD) of 18 μm and 75 % coupling efficiency using a single-mode fiber with MFD of 6.4 μm.
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- Gisselsson Nord, David, et al.
(författare)
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Interphase chromosomal abnormalities and mitotic missegregation of hypomethylated sequences in ICF syndrome cells
- 2005
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Ingår i: Chromosoma. - : Springer Science and Business Media LLC. - 0009-5915 .- 1432-0886. ; 114:2, s. 118-126
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Tidskriftsartikel (refereegranskat)abstract
- The immunodeficiency, centromeric region instability, facial anomalies (ICF) syndrome is a rare autosomal recessive disease. Usually, it is caused by mutations in the DNA methyltransferase 3B gene, which result in decreased methylation of satellite DNA in the juxtacentromeric heterochromatin at 1qh, 16qh, and 9qh. Satellite II-rich 1qh and 16qh display high frequencies of abnormalities in mitogen-stimulated ICF lymphocytes without these cells being prone to aneuploidy. Here we show that in lymphoblastoid cell lines from four ICF patients, there was increased colocalization of the hypomethylated 1qh and 16qh sequences in interphase, abnormal looping of pericentromeric DNA sequences at metaphase, formation of bridges at anaphase, chromosome 1 and 16 fragmentation at the telophase-interphase transition, and, in apoptotic cells, micronuclei with overrepresentation of chromosome 1 and 16 material. Another source of anaphase bridging in the ICF cells was random telomeric associations between chromosomes. Our results elucidate the mechanism of formation of ICF chromosome anomalies and suggest that 1qh-16qh associations in interphase can lead to disturbances of mitotic segregation, resulting in micronucleus formation and sometimes apoptosis. This can help explain why specific types of 1qh and 16qh rearrangements are not present at high frequencies in ICF lymphoid cells despite diverse 1qh and 16qh aberrations continuously being generated.
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- Pålsson, Sara, et al.
(författare)
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Methods for detailed histopathological investigation and localization of biopsies from cervix uteri to improve the interpretation of auto fluorescence data
- 2006
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Ingår i: Journal of Environmental Pathology and Toxicology. - 2162-6537. ; 25:1-2, s. 321-340
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence spectroscopy is one of many optical methods that are potentially clinically useful for noninvasive detection and characterization of disorders on the cervical part of uterus, including precancerous lesions. The cervix uteri exhibits a biologically complex tissue and the morphology of a biopsy is generally not homogenous. The standard histopathological protocol accounts only for the most severe condition found within the biopsy and no information is given on other constituents potentially influencing the recorded fluorescence spectra. Spectra are usually correlated, using multivariate techniques, to the histopathological diagnosis of the biopsies. Since the probe volume of fluorescence spectroscopy is considerably smaller than the extension of the biopsy, this can cause problems in the search for correlation between the fluorescence signals and the pathological structures. In addition, the orientation and location of the biopsies are normally not recorded. We now report on the first detailed histopathological protocol where numerous tissue parameters, such as thickness and type of the epithelium and the number of blood vessels, glands, and inflammatory cells, are tabulated and the orientation and location of the biopsy are recorded as precisely as possible. Hopefully, the use of this protocol together with sophisticated mathematical methods will increase the probability to classify cervical disorders of the uterus, including precancerous lesions, with high sensitivity and specificity.
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