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Well characterised tephra horizons deposited in various sedimentary environments provide a means of synchronising sedimentary archives. The use of tephra as a chronological tool is however still widely underutilised in southern Chile and Argentina. In this study we develop a postglacial tephrochronological model for the Chilean Lake District (ca. 38 to 42°S) by integrating terrestrial and lacustrine records. Tephra deposits preserved in lake sediments record discrete events even if they do not correspond to primary fallout. By combining terrestrial with lacustrine records we obtain the most complete tephrostratigraphic record for the area to date. We present glass geochemical and chronological data for key marker horizons that may be used to synchronise sedimentary archives used for palaeoenvironmental palaeoclimatological and palaeoseismological purposes. Most volcanoes in the studied segment of the Southern Volcanic Zone between Llaima and Calbuco have produced at least one regional marker deposit resulting from a large explosive eruption (magnitude = 4) some of which now have a significantly improved age estimate (e.g. the 10.5 ka Llaima Pumice eruption from Llaima volcano). Others including several units from Puyehue Cordón Caulle are newly described here. We also find tephra related to the Cha1 eruption from Chaitén volcano in lake sediments up to 400 km north from source. Several clear marker horizons are now identified that should help refine age model reconstructions for various sedimentary archives. Our chronological model suggests three distinct phases of eruptive activity impacting the area with an early to mid Holocene period of relative quiescence. Extending our tephrochronological framework further south into Patagonia will allow a more detailed evaluation of the controls on the occurrence and magnitude of explosive eruptions throughout the postglacial.

Reye syndrome, characterised by the combination of liver disease and noninflammatory encephalopathy, is a non-specific clinicopathological entity and a descriptive term covering a group of heterogeneous disorders. Nowadays, some of these patients are diagnosed more correctly as having infectious, metabolic, toxic or other disease. The non-specific case definition implies that the epidemiological studies suggesting a link with acetylsalicylic acid have been performed on a heterogeneous group of children, whereby the value of these studies and their ensuing hypothesis is weakened. Moreover, a detailed analysis of the epidemiological surveys of the Centers for Disease Control, the Yale study and of the British risk factor study provides evidence that not only the use of acetylsalicylic acid but also that of phenothiazines and other anti-emetics is significantly greater in Reye syndrome cases than in controls. As to the decline of Reye syndrome, recent literature data reveal that this is related to more accurate modern diagnosis of infectious, metabolic or toxic disease, reducing the percentage of idiopathic or true cases of Reye syndrome.Reye syndrome is a non-specific descriptive term covering a group of heterogeneous disorders. Moreover, not only the use of acetylsalicylic acid but also of antiemetics is statistically significant in Reye syndrome cases. Both facts weaken the validity of the epidemiological surveys suggesting a link with acetylsalicylic acid.

Editor—The paper by McGovern et al is based on a non-specific definition and an outdated concept of Reye's syndrome in spite of recent convincing data relating to this issue.1 Reye's syndrome is no longer a specific clinicopathological entity but a descriptive term covering a group of heterogeneous disorders of infectious, metabolic, or toxic aetiology.2 All symptoms in the first case, including the neurological complications, can be explained by the influenza A infection.2 Moreover, the confusion lasting for only 48 hours might have been the result of using antiemetics in a patient who had been vomiting almost hourly for 24 hours.2 Urine toxicology screening does not exclude this additional complication. In the second case, exhaustive virological investigations and liver biopsy were not performed, and the metabolic screening is incomplete. In both patients the diagnosis of Reye's syndrome is therefore put forward—in the best case—by default. We are surprised that McGovern et al ignore the misleading biases in the epidemiological studies suggesting a link between Reye's syndrome and aspirin.2,3 The studies were performed on series of children with heterogeneous disorders, which already invalidates their results. In the studies that recorded correctly all drugs given before admission, the use of not one but two drugs was significant—namely, aspirin and antiemetics.2 Neither is the decline of Reye's syndrome an argument for a link with aspirin; evidence shows that this decline is the result of medical progress leading to more correct diagnosis of infectious, metabolic, or toxic disease.2,4 When promoting paracetamol and ibuprofen it would be wise not to conceal their side effects—for example, the hepatotoxicity of paracetamol, which can occur even at minor overdoses given during a few days. This was documented by Rivera-Penera et al and discussed in an accompanying editorial by Heubi and Bien, who assumed that the estimates of the occurrence of paracetamol toxicity are the tip of the iceberg of the total number of cases seen in the United States.5 We end with a question about the five cases seen over 13 years mentioned by McGovern et al in their introduction. Two cases occurred in February 1999, and in both the child had been given aspirin. What had been given to the other children?

Sublacustrine landslide stratigraphy is considered useful for quantitative paleoseismology in low seismicity settings. However as the recharging of underwater slopes with sediments is one of the factors that governs the recurrence of slope failures it is not clear if landslide deposits can provide continuous paleoseismic records in settings of frequent strong shaking. To test this we selected three lakes in south central Alaska that experienced a strong historical megathrust earthquake (the 1964 Mw9.2 Great Alaska Earthquake) and exhibit high sedimentation rates in their main basins (0.2 cm yr- 1–1.0 cm yr- 1). We present high resolution reflection seismic data (3.5 kHz) and radionuclide data from sediment cores in order to investigate factors that control the establishment of a reliable landslide record. Seismic stratigraphy analysis reveals the presence of several landslide deposits in the lacustrine sedimentary infill. Most of these landslide deposits can be attributed to specific landslide events as multiple landslide deposits sourced from different lacustrine slopes occur on a single stratigraphic horizon. We identify numerous events in the lakes: Eklutna Lake proximal basin (14 events) Eklutna Lake distal basin (8 events) Skilak Lake (7 events) and Kenai Lake (7 events). The most recent event in each basin corresponds to the historic 1964 megathrust earthquake. All events are characterized by multiple landslide deposits which hints at a regional trigger mechanism such as an earthquake (the synchronicity criterion). This means that the landslide record in each basin represents a record of past seismic events. Based on extrapolation of sedimentation rates derived from radionuclide dating we roughly estimate a mean recurrence interval in the Eklutna Lake proximal basin Eklutna Lake distal basin Skilak Lake and Kenai Lake at 250 yrs. 450 yrs. 900 yrs. and 450 yrs. respectively. This distinct difference in recording can be explained by variations in preconditioning factors like slope angle slope recharging (sedimentation rate) and the sediment source area: faster slope recharging and a predominance of delta and alluvial fan failures increase the sensitivity and lower the intensity threshold for slope instability. Also the seismotectonic setting of the lakes has to be taken into account. This study demonstrates that sublacustrine landslides in several Alaskan lakes can be used as reliable recorders of strong earthquake shaking when a multi lake approach is used and can enhance the temporal and spatial resolution of the paleoseismic record of south central Alaska.

A case of Moya-Moya disease confirmed by cerebral angiography in a 10-year-old girl is reported. Hypertrophic collateral circulation is easily visualized by MRI. MR angiography very accurately demonstrated the vascular obstruction and the collateral circulation. As MR angiography is not invasive, it promises to become a valuable alternative to conventional angiography in the diagnosis of Moya-Moya.

Between December 1981 and March 1994, 24 patients with a myelodysplastic syndrome (MDS) underwent allogeneic bone marrow transplantation (BMT) for RA with trilineage dysplasia (n = 4), CMML (n = 1), RAEB (n = 4), RAEBt (n = 9) and AML following MDS (n = 6). Fifteen patients (two RAEB, seven RAEBt and six sAML) received chemotherapy before BMT resulting in complete remission in 10 patients (six RAEBt and four sAML) at the time of BMT. Sixteen marrow donors were genotypically HLA-identical siblings. Remaining donors were other family members (five) or unrelated donors (three). The status of the underlying disease at the time of conditioning was the major factor determining long-term survival. The disease-freed survival of RA patients and patients presenting with RAEB, RAEBt and AML but transplanted in complete remission, was respectively 50 and 60%. On the contrary, none of the nine high-risk MDS patients transplanted with persistent disease, survived. Outcome after transplantation with alternative donors was inferior with one long-term survivor, mainly related to the high incidence of severe acute GVHD and its accompanying infectious complications. Six patients relapsed resulting in an actuarial probability of relapse of 28%. Twelve patients died of transplant-related complications leading to a non-relapse mortality at 5 years of 50%. At present eight patients are alive and disease-free 20 to 132 months post-transplantation resulting in an actuarial 5-year disease-free survival of 40.7%. Our results suggest that allogeneic bone marrow transplantation is a feasible treatment option for patients with MDS. However, improvement in GVHD prophylaxis and supportive care to reduce transplant-treated mortality and improved relapse prevention are imperative.

In dit proefschrift beschrijven we een specifieke klasse van numerieke methoden voor het oplossen van Sturm-Liouville en Schrodinger vergelijkingen. Ook de Matlab-implementatie van de methoden wordt besproken.