| 1. |
- Olsson, Teresia, et al.
(författare)
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Pulse-Picking by Resonant Excitation (PPRE) for Timing Users at the MAX IV 3 GeV Storage Ring
- 2018
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Ingår i: 9th International Particle Accelerator Conference. - 9783954501847 ; , s. 4300-4303
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- At synchrotron light storage rings there is demand for serving both high-brilliance and timing users simultaneously. At many rings this is commonly achieved by operating fill patterns with gaps of sufficient length, but this is not favorable for rings that operate with passive harmonic cavities to damp instabilities and increase Touschek lifetime by lengthening the bunches. For such rings, gaps in the fill pattern could severely reduce the achievable bunch lengths. For the MAX IV 3 GeV storage ring, sufficient bunch lengthening is also essential for conserving the ultralow emittance and reducing heat load on vacuum components at high current. It is therefore of interest to study methods to serve timing users while operating without gap in the fill pattern. Once such method is PPRE, where the transverse emittance of one bunch in the bunch train is increased by an incoherent betatron excitation. This paper presents simulations for the MAX IV 3 GeV storage ring and discusses the machine requirements as well as the achievable performance for timing users.
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| 2. |
- Ferreyra Vega, Sandra, et al.
(författare)
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Longitudinal DNA methylation analysis of adult-type IDH-mutant gliomas.
- 2023
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Ingår i: Acta neuropathologica communications. - : Springer Science and Business Media LLC. - 2051-5960. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Diffuse gliomas are the most prevalent malignant primary brain tumors in adults and remain incurable despite standard therapy. Tumor recurrence is currently inevitable, which contributes to a persistent high morbidity and mortality in these patients. In this study, we examined the genome-wide DNA methylation profiles of primary and recurrent adult-type IDH-mutant gliomas to elucidate DNA methylation changes associated with tumor progression (with or without malignant transformation). We analyzed DNA methylation profiles of 37 primary IDH-mutant gliomas and 42 paired recurrences using the DNA methylation EPIC beadChip array. DNA methylation-based classification reflected the tumor progression over time. We observed a methylation subtype switch in a proportion of IDH-mutant astrocytomas; the primary tumors were subclassified as low-grade astrocytomas, which progressed to high-grade astrocytomas in the recurrent tumors. The CNS WHO grade 4 IDH-mutant astrocytomas did not always resemble methylation subclasses of higher grades. The number of differentially methylated CpG sites increased over time, and astrocytomas accumulated more differentially methylated CpG sites than oligodendrogliomas during tumor progression. Few differentially methylated CpG siteswere shared between patients. We demonstrated that DNA methylation profiles are mostly maintained during IDH-mutant glioma progression, but CpG site-specific methylation alterations can occur.
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| 3. |
- Ferreyra Vega, Sandra, et al.
(författare)
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Spatial heterogeneity in DNA methylation and chromosomal alterations in diffuse gliomas and meningiomas
- 2022
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Ingår i: Modern Pathology. - : Elsevier BV. - 0893-3952. ; 35:11, s. 1551-1561
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Tidskriftsartikel (refereegranskat)abstract
- Adult-type diffuse gliomas and meningiomas are the most common primary intracranial tumors of the central nervous system. DNA methylation profiling is a novel diagnostic technique increasingly used also in the clinic. Although molecular heterogeneity is well described in these tumors, DNA methylation heterogeneity is less studied. We therefore investigated the intratumor genetic and epigenetic heterogeneity in diffuse gliomas and meningiomas, with focus on potential clinical implications. We further investigated tumor purity as a source for heterogeneity in the tumors. We analyzed genome-wide DNA methylation profiles generated from 126 spatially separated tumor biopsies from 39 diffuse gliomas and meningiomas. Moreover, we evaluated five methods for measurement of tumor purity and investigated intratumor heterogeneity by assessing DNA methylation-based classification, chromosomal copy number alterations and molecular markers. Our results demonstrated homogeneous methylation-based classification of IDH-mutant gliomas and further corroborates subtype heterogeneity in glioblastoma IDH-wildtype and high-grade meningioma patients after excluding samples with low tumor purity. We detected a large number of differentially methylated CpG sites within diffuse gliomas and meningiomas, particularly in tumors of higher grades. The presence of CDKN2A/B homozygous deletion differed in one out of two patients with IDH-mutant astrocytomas, CNS WHO grade 4. We conclude that diffuse gliomas and high-grade meningiomas are characterized by intratumor heterogeneity, which should be considered in clinical diagnostics and in the assessment of methylation-based and molecular markers.
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| 4. |
- Kling, Teresia, 1985, et al.
(författare)
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Refinement of prognostication for IDH-mutant astrocytomas using DNA methylation-based classification
- 2024
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Ingår i: BRAIN PATHOLOGY. - 1015-6305 .- 1750-3639.
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Tidskriftsartikel (refereegranskat)abstract
- The 2021 World Health Organization (WHO) grading system of isocitrate dehydrogenase (IDH)-mutant astrocytomas relies on histological features and the presence of homozygous deletion of the cyclin-dependent kinase inhibitor 2A and 2B (CDKN2A/B). DNA methylation profiling has become highly relevant in the diagnosis of central nervous system (CNS) tumors including gliomas, and it has been incorporated into routine clinical diagnostics in some countries. In this study, we, therefore, examined the value of DNA methylation-based classification for prognostication of patients with IDH-mutant astrocytomas. We analyzed histopathological diagnoses, genome-wide DNA methylation array data, and chromosomal copy number alteration profiles from a cohort of 385 adult-type IDH-mutant astrocytomas, including a local cohort of 127 cases and 258 cases from public repositories. Prognosis based on WHO 2021 CNS criteria (histological grade and CDKN2A/B homozygous deletion status), other relevant chromosomal/gene alterations in IDH-mutant astrocytomas and DNA methylation-based subclassification according to the molecular neuropathology classifier were assessed. We demonstrate that DNA methylation-based classification of IDH-mutant astrocytomas can be used to predict outcome of the patients equally well as WHO 2021 CNS criteria. In addition, methylation-based subclassification enabled the identification of IDH-mutant astrocytoma patients with poor survival among patients with grade 3 tumors and patients with grade 4 tumors with a more favorable outcome. In conclusion, DNA methylation-based subclassification adds prognostic information for IDH-mutant astrocytomas that can further refine the current WHO 2021 grading scheme for these patients.
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| 5. |
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| 6. |
- Olsson, Teresia, et al.
(författare)
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Bunch Length Measurements with Passive Harmonic Cavities for Non-Uniform Fill Patterns in a 100 MHz RF
- 2016
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Ingår i: IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference. - 9783954501472 ; , s. 2918-2921
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The MAX IV facility includes two storage rings operated at 1.5 GeV and 3 GeV, which are both designed to operate with a uniform, multibunch fill pattern. Both rings have a 100 MHz RF system and employ passive harmonic cavities to damp instabilities and increase Touschek lifetime. Recently, a discussion on timing modes at the MAX IV storage rings has been initiated by the user community. Creating opportunities for timing experiments implies operating the rings with other fill patterns than the planned multibunch mode. Such operation can, however, cause transient effects in the passive harmonic cavities which affect the performance of the machine. It is therefore of interest to study the effect on the beam when operating with non-uniform fill patterns. This paper presents bunch length measurements at the 100 MHz MAX II storage ring for fill patterns with gaps. The purpose of the measurements was to evaluate the employed measurement method and simulation codes for future studies of various alternate fill patterns in the MAX IV storage rings.
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| 7. |
- Olsson, Teresia, et al.
(författare)
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Bunch Length Measurements with Passive Harmonic Cavities for Uniform Fill Patterns in a 100 MHz RF System
- 2016
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Ingår i: Proceedings of IPAC2016, Busan, Korea. - 9783954501472 ; , s. 2914-2917
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The MAX IV facility includes two storage rings operated at 1.5 GeV and 3 GeV. Both rings make use of a 100 MHz RF system and are designed to operate with a uniform multibunch fill pattern aswell as employ passive harmonic cavities to damp instabilities and increase Touschek lifetime. Recently, a discussion on timing modes at the MAX IV storage rings has been initiated by the user community. This implies operating the rings with other fill patterns than the originally planned multibunch mode and therefore detailed studies of the performance of the harmonic cavities are of interest. This paper presents bunch length measurements at the 100 MHz MAX II storage ring for uniform fill patterns. The purpose of the measurements was to evaluate the employed measurement method and simulation codes for future studies of fill patterns in the MAX IV storage rings.
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| 8. |
- Olsson, Teresia, et al.
(författare)
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First Measurements of Pulse Picking by Resonant Excitation (PPRE) at the MAX IV 3 GeV Storage Ring
- 2017
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Ingår i: Proceedings of IPAC2017, Copenhagen, Denmark. ; , s. 2750-2752
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- At synchrotron light storage rings there is demand for serving high-brilliance users requesting multibunch operation while simultaneously serving timing users who require single-bunch operation. One method to accomplish this is PPRE developed and currently in user operation at BESSY II. In the method, the transverse emittance of one of the bunches in the bunch train is increased by an incoherent betatron excitation. Part of the light from this bunch can then be separated from the multibunch light by an aperture in the beamline, resulting in single-bunch light for the experiment. Methods such as this expand the scope of storage rings without requiring special fill patterns. This is of growing interest due to the upgrade trend towards diffraction-limited storage rings where it becomes more challenging to operate with inhomogeneous fill patterns. Measurements of PPRE were performed at the MAX IV 3 GeV storage ring utilizing the bunch-by-bunch feedback system both for excitation and as a diagnostic. Furthermore, measurements involving direct beam imaging at the diagnostics beamline allowed quantifying the effect of this excitation on the horizontal and vertical emittance.
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| 9. |
- Olsson, Teresia, et al.
(författare)
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High-chromaticity Optics for the MAX IV 1.5 GeV Storage Ring
- 2014
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Ingår i: Proceedings of IPAC’14. - 9783954501151 ; , s. 3053-3055
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The MAX IV facility currently under construction in Lund, Sweden will include a 1.5 GeV storage ring. To prevent head-tail instability, the negative natural chromaticities of the MAX IV 1.5 GeV storage ring have been corrected to positive values using sextupole gradients in the focusing quadrupoles along with dedicated sextupole magnets. To allow adjustment of the chromaticity correction, weak correction sextupoles have been inserted into the lattice. A high-chromaticity optics has been developed for the MAX IV 1.5 GeV storage ring in case instability issues arise during commissioning. Two chromatic sextupole families were used to correct the linear chromaticity. The tune footprint was then tailored using the remaining two sextupole families with the goal of maximizing dynamic aperture and Touschek lifetime. This paper describes the recently developed high-chromaticity optics for the MAX IV 1.5 GeV storage ring and discusses performance limitations of the optics constrained by available gradient strength in the sextupoles.
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| 10. |
- Olsson, Teresia, et al.
(författare)
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High-Chromaticity Optics for the MAX IV 3 GeV Storage Ring
- 2013
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Ingår i: PAC 2013 Proceedings. - 9783954501380 ; , s. 592-594
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The ultralow emittance lattice of the MAX IV 3 GeV storage ring has a large negative natural chromaticity. This has to be corrected to positive values to prevent head-tail instabilities. On the other hand, high linear chromaticity can lead to a large tune footprint which limits Touschek lifetime. Therefore, the linear chromaticity is corrected to +1.0 in both planes with sextupoles while octupoles are used to further reduce the tune footprint. Studies indicate this design leads to threshold currents for resistive wall and transverse mode coupling instabilities beyond what is expected during regular user operation. However, since these are only preliminary studies based on approximations, the possibility of instability issues during commissioning needs to be considered. An inexpensive, short term solution is to operate the storage ring at a higher chromaticity. This paper describes the development of a high-chromaticity optics for the MAX IV 3 GeV storage ring. It focuses on reduction of chromatic and amplitude-dependent tune shifts to maximize dynamic aperture and Touschek lifetime. A comparison between the performance of the new high-chromaticity optics and the design optics is also presented.
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