Het effect van transversale modi in een golfpijp-resonator op de resonantieconditie van een Compton Vrije-Elktronen-Laser

In een Vrije-Elektronen-Laser (FEL), waar de resonator de structuur heeft van een golfpijp, heeft de fasesnelheid van het licht een significante impact op de golflengte van het gegenereerde licht. Dit is een effect dat bekend is in Raman-FEL’s maar het is minder bekend dat het ook een belangrijke rol kan spelen in Compton FEL’s. Het effect is experimenteel geverifieerd in onze 6 MeV Compton FEL. De FEL heeft een golfpijp-resonator met vlakke eindspiegels waarin concentrisch een gat is gemaakt voor de inkoppeling van de elektronen en de uitkoppeling van het licht. Opeenvolgende transversale modes, die elk hun eigen fasesnelheid hebben, zijn duidelijk in het golflengte spectrum te onderscheiden. Gelijktijdige resonanties met een golflengte verschil van 5% zijn gemeten. In gangbare lasers is dit verschil doorgaans niet groter dan 0.1%

The "TEU-FEL" project

The free-electron laser of the TEU-FEL project will be based on a 6 MeV photo-cathode linac as injector, a 25 MeV race-track microtron as main accelerator and a hybrid, 25 mm period undulator. The project will be carried out in two phases. In phase one only the 6 MeV linac will be used, The FEL will then produce tunable radiation around 200 µm. In phase two the linac will be used as an injector for the microtron. The FEL will then produce tunable radiation around 10 µm. Technical information will be presented on the different subsystems

Vrije-Elektronen-Laser werk aan de Universiteit van Twente in samenwerking met het Nederlands Centrum voor Laser Research

In de vakgroep Quantum Elektronica van de Faculteit Technische Natuurkunde aan de Universiteit Twente zijn momenteel drie Vrije-Elektronen-Laser projecten operationeel. De projecten worden uitgevoerd in nauwe samenwerking met het Nederlands Centrum voor Laser Research. Het FEL-onderzoek binnen de vakgroep richt zich met name op de fysische aspecten van het FEL-mechanisme en de technologische ontwikkeling van componenten voor een effectieve produktie van straling. Ook wordt veel aandacht besteed aan de ontwikkeling van diagnostiek, zowel voor de elektronenbundel als voor de optische bundel. Veel componenten zijn in huis ontwikkeld en gebouwd. Op deze wijze wordt getracht FEL’s aantrekkelijk te maken voor industriële toepassingen. Dit laatste aspect krijgt met name veel aandacht in de samenwerking met het NCLR. Hieronder volgt een korte beschrijving van de verschillende projecten

Orthostatic hypotension and novel blood pressure-associated gene variants: Genetics of Postural Hemodynamics (GPH) Consortium

Aims Orthostatic hypotension (OH), an independent predictor of mortality and cardiovascular events, strongly correlates with hypertension. Recent genome-wide studies have identified new loci influencing blood pressure (BP) in populations, but their impact on OH remains unknown. Methods and resultsA total of 38 970 men and women of European ancestry from five population-based cohorts were included, of whom 2656 (6.8) met the diagnostic criteria for OH (systolic/diastolic BP drop <20/10 mmHg within 3 min of standing). Thirty-one recently discovered BP-associated single nucleotide polymorphisms (SNPs) were examined using an additive genetic model and the major allele as referent. Relations between OH, orthostatic systolic BP response, and genetic variants were assessed by inverse variance-weighted meta-analysis. We found Bonferroni adjusted (P < 0.0016) significant evidence for association between OH and the EBF1 locus (rs11953630, per-minor-allele odds ratio, 95 confidence interval: 0.90, 0.850.96; P=0.001), and nominal evidence (P < 0.05) for CYP17A1 (rs11191548: 0.85, 0.750.95; P=0.005), and NPR3-C5orf23 (rs1173771: 0.92, 0.870.98; P=0.009) loci. Among subjects not taking BP-lowering drugs, three SNPs within the NPPA/NPPB locus were nominally associated with increased risk of OH (rs17367504: 1.13, 1.021.24; P=0.02, rs198358: 1.10, 1.011.20; P=0.04, and rs5068: 1.22, 1.041.43; P=0.01). Moreover, an ADM variant was nominally associated with continuous orthostatic systolic BP response in the adjusted model (P=0.04). ConclusionThe overall association between common gene variants in BP loci and OH was generally weak and the direction of effect inconsistent with resting BP findings. These results suggest that OH and resting BP share few genetic components

The diagnostic work-up and outcomes of ‘presumed’ idiopathic acute pancreatitis: A post-hoc analysis of a multicentre observational cohort

Introduction: After standard diagnostic work-up, the aetiology of acute pancreatitis remains unknown in 16–27% of cases, a condition referred to as idiopathic acute pancreatitis (IAP). Determining the aetiology of pancreatitis is essential, as it may direct treatment in the acute phase and guides interventions to prevent recurrent pancreatitis. Methods: Between 2008 and 2015, patients with acute pancreatitis were registered prospectively in 19 Dutch hospitals. Patients who had a negative initial diagnostic work-up with regard to the underlying aetiology of their pancreatitis were labelled ‘presumed’ IAP. The aim of this study was to assess the use of diagnostic modalities and their yield to establish an aetiology in ‘presumed’ IAP, and to assess recurrence rates both with and without treatment. Results: Out of the 1632 registered patients, 191 patients had a first episode of ‘presumed’ IAP, of whom 176 (92%) underwent additional diagnostic testing: CT (n = 124, diagnostic yield 8%), EUS (n = 62, yield 35%), MRI/MRCP (n = 56, yield 33%), repeat ultrasound (n = 97, yield 21%), IgG4 (n = 54, yield 9%) and ERCP (n = 15, yield 47%). In 64 of 176 patients (36%) an aetiological diagnosis was established, mostly biliary (n = 39). In 13 out of 176 of patients (7%) a neoplasm was diagnosed. If additional diagnostic workup revealed an aetiology, the recurrence rate was lower in the treated patients than in the patients without a definite aetiology (15% versus 43%, p = 0.014). Conclusion: Additional diagnostic testing revealed an aetiology in one-third of ‘presumed’ IAP patients. The aetiology found was mostly biliary, but occasionally neoplasms were found. Identification of an aetiology with subsequent treatment reduced the rate of recurrence

Parental origin of sequence variants associated with complex diseases

To access publisher full text version of this article. Please click on the hyperlink in Additional Links fieldEffects of susceptibility variants may depend on from which parent they are inherited. Although many associations between sequence variants and human traits have been discovered through genome-wide associations, the impact of parental origin has largely been ignored. Here we show that for 38,167 Icelanders genotyped using single nucleotide polymorphism (SNP) chips, the parental origin of most alleles can be determined. For this we used a combination of genealogy and long-range phasing. We then focused on SNPs that associate with diseases and are within 500 kilobases of known imprinted genes. Seven independent SNP associations were examined. Five-one with breast cancer, one with basal-cell carcinoma and three with type 2 diabetes-have parental-origin-specific associations. These variants are located in two genomic regions, 11p15 and 7q32, each harbouring a cluster of imprinted genes. Furthermore, we observed a novel association between the SNP rs2334499 at 11p15 and type 2 diabetes. Here the allele that confers risk when paternally inherited is protective when maternally transmitted. We identified a differentially methylated CTCF-binding site at 11p15 and demonstrated correlation of rs2334499 with decreased methylation of that site.info:eu-repo/grantAgreement/EC/FP7/21807

Endoscopic Versus Surgical Step-Up Approach for Infected Necrotizing Pancreatitis (ExTENSION): Long-term Follow-up of a Randomized Trial

BACKGROUND & AIMS: Previous randomized trials, including the Transluminal Endoscopic Step-Up Approach Versus Minimally Invasive Surgical Step-Up Approach in Patients With Infected Pancreatic Necrosis (TENSION) trial, demonstrated that the endoscopic step-up approach might be preferred over the surgical step-up approach in patients with infected necrotizing pancreatitis based on favorable short-term outcomes. We compared long-term clinical outcomes of both step-up approaches after a period of at least 5 years. METHODS: In this long-term follow-up study, we reevaluated all clinical data on 83 patients (of the originally 98 included patients) from the TENSION trial who were still alive after the initial 6-month follow-up. The primary end point, similar to the TENSION trial, was a composite of death and major complications. Secondary end points included individual major complications, pancreaticocutaneous fistula, reinterventions, pancreatic insufficiency, and quality of life. RESULTS: After a mean followup period of 7 years, the primary end point occurred in 27 patients (53%) in the endoscopy group and in 27 patients (57%) in the surgery group (risk ratio [RR], 0.93; 95% confidence interval [CI], 0.65-1.32; P = .688). Fewer pancreaticocutaneous fistulas were identified in the endoscopy group (8% vs 34%; RR, 0.23; 95% CI, 0.08-0.83). After the initial 6-month follow-up, the endoscopy group needed fewer reinterventions than the surgery group (7% vs 24%; RR, 0.29; 95% CI, 0.09-0.99). Pancreatic insufficiency and quality of life did not differ between groups. CONCLUSIONS: At long-term follow-up, the endoscopic step-up approach was not superior to the surgical step-up approach in reducing death or major complications in patients with infected necrotizing pancreatitis. However, patients assigned to the endoscopic approach developed overall fewer pancreaticocutaneous fistulas and needed fewer reinterventions after the initial 6-month follow-up.Cellular mechanisms in basic and clinical gastroenterology and hepatolog

Meta-analysis of type 2 Diabetes in African Americans Consortium

Type 2 diabetes (T2D) is more prevalent in African Americans than in Europeans. However, little is known about the genetic risk in African Americans despite the recent identification of more than 70 T2D loci primarily by genome-wide association studies (GWAS) in individuals of European ancestry. In order to investigate the genetic architecture of T2D in African Americans, the MEta-analysis of type 2 DIabetes in African Americans (MEDIA) Consortium examined 17 GWAS on T2D comprising 8,284 cases and 15,543 controls in African Americans in stage 1 analysis. Single nucleotide polymorphisms (SNPs) association analysis was conducted in each study under the additive model after adjustment for age, sex, study site, and principal components. Meta-analysis of approximately 2.6 million genotyped and imputed SNPs in all studies was conducted using an inverse variance-weighted fixed effect model. Replications were performed to follow up 21 loci in up to 6,061 cases and 5,483 controls in African Americans, and 8,130 cases and 38,987 controls of European ancestry. We identified three known loci (TCF7L2, HMGA2 and KCNQ1) and two novel loci (HLA-B and INS-IGF2) at genome-wide significance (4.15 × 10(-94)<P<5 × 10(-8), odds ratio (OR)  = 1.09 to 1.36). Fine-mapping revealed that 88 of 158 previously identified T2D or glucose homeostasis loci demonstrated nominal to highly significant association (2.2 × 10(-23) < locus-wide P<0.05). These novel and previously identified loci yielded a sibling relative risk of 1.19, explaining 17.5% of the phenotypic variance of T2D on the liability scale in African Americans. Overall, this study identified two novel susceptibility loci for T2D in African Americans. A substantial number of previously reported loci are transferable to African Americans after accounting for linkage disequilibrium, enabling fine mapping of causal variants in trans-ethnic meta-analysis studies.Peer reviewe