Experimental analysis of Raman-induced transverse mode instability in a core-pumped Raman fiber amplifier.

The effect of transverse mode instability is a limitation for the power scaling of fiber laser systems, that can originate due to heat caused by stimulated Raman scattering. In this contribution, we experimentally investigate the threshold of transverse mode instability caused by stimulated Raman scattering in a passive fiber. Both, the Stokes seed power and the fiber length of a core-pumped Raman fiber amplifier are varied to systematically study this effect.

Influence of pedestal diameter on mode instabilities in Yb/Ce/Al-doped fibers.

In this paper we present numerical and experimental results revealing that the mode instability threshold of highly Yb-doped, Ce/Al co-doped pedestal fibers is affected by the size of the index-increased pedestal structure surrounding the core. An alternative preparation technology for the realization of large mode area fibers with very large Al-doped silica pedestals is introduced. Three different pedestal fiber design iterations characterized by low photodarkening were manufactured and tested in counter-pumped amplifier setups.

Transverse mode instability in a passive fiber induced by stimulated Raman scattering.

Transverse mode instabilities are a major limitation for power scaling of fiber lasers but have so far only been observed in laser-active fibers. In this contribution we present experimental observations of transverse mode instabilities in a passive fiber. In this fiber, stimulated Raman scattering acted as heat source.

Natural quasicrystal with decagonal symmetry.

We report the first occurrence of a natural quasicrystal with decagonal symmetry. The quasicrystal, with composition Al71Ni24Fe5, was discovered in the Khatyrka meteorite, a recently described CV3 carbonaceous chondrite. Icosahedrite, Al63Cu24Fe13, the first natural quasicrystal to be identified, was found in the same meteorite.

Impact-induced shock and the formation of natural quasicrystals in the early solar system.

The discovery of a natural quasicrystal, icosahedrite (Al63Cu24Fe13), accompanied by khatyrkite (CuAl2) and cupalite (CuAl) in the CV3 carbonaceous chondrite Khatyrka has posed a mystery as to what extraterrestrial processes led to the formation and preservation of these metal alloys. Here we present a range of evidence, including the discovery of high-pressure phases never observed before in a CV3 chondrite, indicating that an impact shock generated a heterogeneous distribution of pressures and temperatures in which some portions reached at least 5 GPa and 1,200 °C. The conditions were sufficient to melt Al-Cu-bearing minerals, which then rapidly solidified into icosahedrite and other Al-Cu metal phases.

Parents' and children's perspectives of a children's hospice bereavement program.

The provision of some form of bereavement services is an integral part of any pediatric hospice program. The Canuck Place hospice program has offered bereavement services since it began in 1995. A mixed-method evaluation of the impact of the Canuck Place program on the families it served during its first two-and-a-half years of operation was conducted.

Aberrant somatic hypermutation in tumor cells of nodular-lymphocyte-predominant and classic Hodgkin lymphoma.

Aberrant somatic hypermutation (SHM) has been identified as a mechanism for genomewide instability in diffuse large B-cell lymphoma (DLBCL). To assess whether aberrant SHM plays a role in the molecular pathogenesis of Hodgkin lymphoma (HL), we investigated microdissected neoplastic cells of nodular lymphocyte-predominant HL (NLPHL; n = 10) and classic HL (cHL; n = 9) for the presence of mutations in the 5' sequences of 4 previously identified aberrant SHM targets (PIM1, PAX5, RhoH/TTF, c-MYC). Mutations in one or more genes were detected in 80% of NLPHLs and 55% of cHLs, with 50% and 30% of patients carrying mutations in 2 or more genes, respectively.

Pathogenesis of Hodgkin's lymphoma.

In Hodgkin's lymphoma (HL), the B cell origin of the tumour cells, the Hodgkin and Reed-Sternberg (HRS) cells, has been disclosed by molecular single cell analysis about 10 yr ago. This finding formed the basis for various studies aimed to better understand the pathogenesis of this peculiar malignancy and the pathophysiology of the HRS cells. Work of our groups in this regard was focussed recently on two main topics, namely the study of differential gene expression in HRS cells and the pathogenesis of composite lymphomas.

Insights into the multistep transformation process of lymphomas: IgH-associated translocations and tumor suppressor gene mutations in clonally related composite Hodgkin's and non-Hodgkin's lymphomas.

Clonally related composite lymphomas of Hodgkin's lymphoma (HL) and Non-Hodgkin's lymphoma (NHL) represent models to study the multistep transformation process in tumorigenesis and the development of two distinct tumors from a shared precursor. We analyzed six such lymphomas for transforming events. The HLs were combined in two cases with follicular lymphoma (FL), and in one case each with B-cell chronic lymphocytic leukemia, splenic marginal zone lymphoma, mantle cell lymphoma (MCL) and diffuse large B-cell lymphoma (DLBCL).

Profiling of Hodgkin's lymphoma cell line L1236 and germinal center B cells: identification of Hodgkin's lymphoma-specific genes.

The malignant cells of classical Hodgkin's lymphoma (cHL), Hodgkin and Reed-Sternberg (HRS) cells, appear to be derived from germinal center (GC) B cells in most cases of the disease. Apart from recent findings of constitutive activation of some transcription factors and autocrine stimulation by cytokine receptors, the mechanisms of malignant transformation in cHL still remain poorly understood. We performed a large scale gene expression study using serial analysis of gene expression (SAGE), comparing the cHL cell line L1236 and human GC B cells.

Identification of Hodgkin and Reed-Sternberg cell-specific genes by gene expression profiling.

Hodgkin lymphoma (HL) is a malignancy of unknown pathogenesis. The malignant Hodgkin and Reed/Sternberg (HRS) cells derive from germinal center B cells (or rarely, T cells) but have a heterogeneous and largely uncharacterized phenotype. Using microarrays, we compared the gene expression profile of four HL cell lines with profiles of the main B cell subsets and B cell non-HLs to find out whether HRS cells, despite their described heterogeneity, show a distinct gene expression, to study their relationship to other normal and malignant B cells, and to identify genes aberrantly or overexpressed by HRS cells.

Evidence that Hodgkin and Reed-Sternberg cells in Hodgkin disease do not represent cell fusions.

In most cases, Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin disease (HD) carry rearranged immunoglobulin (Ig) genes and thus derive from B cells. In rare cases, HRS cells originate from T cells. However, based on the unusual immunophenotype of HRS cells, often showing coexpression of markers typical for different hematopoietic lineages, and the regular detection of numerical chromosomal abnormalities, it has been speculated that HRS cells might represent cell fusions.