Real-time determination of laser beam quality by modal decomposition

We present a real-time method to determine the beam propagation ratio M2 of laser beams. The all-optical measurement of modal amplitudes yields M2 parameters conform to the ISO standard method. The experimental technique is simple and fast, which allows to investigate laser beams under conditions inaccessible to other methods.Comment: 8 pages, 4 figures, published in Optics Expres

Metamagnetic phase transition of the antiferromagnetic Heisenberg icosahedron

The observation of hysteresis effects in single molecule magnets like Mn$_{12}$-acetate has initiated ideas of future applications in storage technology. The appearance of a hysteresis loop in such compounds is an outcome of their magnetic anisotropy. In this Letter we report that magnetic hysteresis occurs in a spin system without any anisotropy, specifically, where spins mounted on the vertices of an icosahedron are coupled by antiferromagnetic isotropic nearest-neighbor Heisenberg interaction giving rise to geometric frustration. At T=0 this system undergoes a first order metamagnetic phase transition at a critical field \Bcrit between two distinct families of ground state configurations. The metastable phase of the system is characterized by a temperature and field dependent survival probability distribution.Comment: 4 pages, 4 figures, submitted to Physical Review Letter

Response to combination therapy with interferon alfa-2a and ribavirin in chronic hepatitis C according to a TNF-alpha promoter polymorphism

Background. Tumor necrosis factor-alpha (TNF-alpha) is involved in the pathogenesis of chronic active hepatitis C. Polymorphisms in the promoter region of the TNF-alpha gene can alter the TNF-alpha expression and modify the host immune response. The present study aimed at the correlation of the G308A TNF-alpha polymorphism with the response to antiviral combination therapy in chronic hepatitis C. Patients and Methods: 62 patients with HCV and 119 healthy unrelated controls were genotyped for the G308A TNF-alpha promoter polymorphism. The patients received 3 x 3 million units of interferon alfa-2a and 1,0001,200 mg ribavirin daily according to their body weight. A response was defined as absence of HCV-RNA and normalization of S-ALT after 6 months of combination therapy. Results:With respect to the allele and genotype frequency, a significant difference was not observed between controls and patients with chronic hepatitis C. Furthermore, such a difference was also not observed if responders and non-responders to antiviral therapy were compared. Conclusions: The promoter polymorphism of the TNF-alpha gene investigated herein is equally distributed in healthy individuals and patients with hepatitis C and does not seem to predict the response to therapy with interferon alfa-2a and ribavirin. Copyright (C) 2003 S. Karger AG, Basel

Multifocal High-Grade Pancreatic Precursor Lesions: A Case Series and Management Recommendations

Background: The risk of developing invasive cancer in the remnant pancreas after resection of multifocal high-grade pancreatic precursor lesions is not well known. We report three patients who were followed up after resection of multifocal high-grade pancreatic intraepithelial neoplasia (PanIN)-3 or intraductal papillary mucinous neoplasia (IPMN), two of whom eventually developed invasive carcinoma. Presentation: 1) 68-year-old woman who had a laparoscopic distal pancreatectomy for multifocal mixed-type IPMN, identified as high-grade on final pathology, with negative surgical margins. During semiannual monitoring, eight years from the first surgery, the patient developed suspicious features prompting surgical resection of the body with final pathology revealing invasive ductal adenocarcinoma in the setting of IPMN. 2) 48-year-old woman who had a distal pancreatectomy for severe acute/chronic symptomatic pancreatitis, with final pathology revealing multifocal high-grade PanIN-3, with negative surgical margins. Despite semiannual monitoring, two years from the first surgery, the patient developed pancreatic adenocarcinoma with liver metastasis. 3) 55-year-old woman who had a Whipple procedure for symptomatic chronic pancreatitis, with multifocal PanIN-3 on final pathology. The patient underwent completion pancreatectomy due to symptomatology and her high-risk profile, with final pathology confirming multifocal PanIN-3. Conclusion: Multifocal high-grade dysplastic lesions of the pancreas might benefit from surgical resection

Assessing the Hydraulics of Water Heaters by Adding Fluoride as a Tracer to Inform its Overall Effect on Water Quality

As residential water heaters are the primary source of waterborne disease outbreaks in the U.S. there is a need to better understand how they are contributing to decreased water quality in buildings. Previous work has indicated that intermittent stagnation, low disinfection residual and operation temperatures promote the growth of pathogens in water heaters. The overall effect of hydrodynamics of water heaters on these factors remains unclear. Therefore, a tracer study was performed to determine the effect of and characterize hydraulics of the typical residential water heater on water quality. Controlling temperature and flow rate, a pilot-scale hot water system (50 gal) with specially adapted fittings was used. The fittings allowed for injection of fluoride as a tracer. 4.40 mg/L fluoride solution was injected at room temperature into the inlet line, set at 2.50 gal/min, to derive a step input fluoride concentration. Samples were obtained at the outlet of the tank, then fluoride concentration was measured by ion chromatography. A model was derived numerically in Matlab to validate if the experimental data reflected the behavior of a continuous stirred tank reactor. The data was consistent with the model but deviated at high flow rate and temperature conditions indicating that dispersion effects may be a factor. Additional tests with this tracer can help to better evaluate hydrodynamics of the system and thus its impact on water quality before it reaches the point of use