Cyclobutenes by Platinum-Catalyzed Cycloisomerization Reactions of Enynes

1,6-Enynes bearing (electron-rich) aryl substituents on their alkyne moiety rearrange to cyclobutene derivatives in the presence of catalytic amounts of PtCl2 in toluene. The reaction is significantly accelerated when performed under an atmosphere of CO (1 atm), most likely by increasing the electrophilicity of the metal template by temporary coordination to this π-acidic ligand. This transformation allows the build up of considerable strain in the products as witnessed by the productive formation of tricyclic skeletons, such as 7 or 9. Moreover, these products provide evidence for the mechanistic scenario of platinum-catalyzed cycloisomerization reactions previously proposed, which are thought to proceed via organo−platinum species that mimic the reactivity of metal-complexed “nonclassical” carbocations

Improving the efficiency of CTDIw annual measurements with established 16 cm: 32 cm phantom ratios

Purpose: To validate the use of the 16 cm CTDI phantom to estimate the 32 cm phantom CTDIw with tabulated data from previous years.Methods: A retrospective analysis of CTDI measurements was performed from the annual physics testing reports of four Siemens Symbia (Emotion) T6, one Siemens Symbia (Emotion) T16, one Siemens Sensation Open, one Siemens Sensation 16, one Siemens Sensation 32, two GE LightSpeed 16 and five GE VCT CT scanners. For each annual report, the ratio of the 16 cm: 32 cm CTDI phantom measurements was calculated from mAs-normalized CTDI100. The ratios from a) the acceptance test, b) one year after the acceptance test or c) an average ratio of all of the previous years (range 4-8 years), were then used to estimate 32 cm CTDI phantom measurements based on active 16 cm CTDI measurements. The average percent difference between measured and calculated CTDIw was determined per scanner for all years.Results: The most accurate results were obtained when using the average ratios of all the previous years, -2% to 3% difference across all scanner models. For the ratios of the year after the acceptance test, the difference ranged from -3% to 7%, while the data estimated from the acceptance testing results yielded the largest percent difference -4% to 8%. The 64-detector row system estimates displayed the greatest variation, followed by the 16-detector row scanners, while the 6-detector row system estimates were the most accurate.Conclusion: Compared to the Siemens and GE specified CTDI limits of ± 15-30% , the variation in the estimated 32 cm phantom CTDIw values was 2-15 times lower, dependent on the scanner model and method of estimation. The variation was considerably less (2-3%) with ratios of all the previous years, perhaps indicative of year to year variations that can result in greater error.------------------------------Cite this article as: Dodge C, Gress D. Improving the efficiency of CTDIw annual measurements with established 16 cm: 32 cm phantom ratios. Int J Cancer Ther Oncol 2014; 2(2):020220. DOI: 10.14319/ijcto.0202.2

Emerging concepts in pancreatic cancer medicine: targeting the tumor stroma

Pancreatic ductal adenocarcinoma is a stroma-rich and highly challenging cancer to treat. Over recent years, it has become increasingly evident that the complex network of soluble cytokines, growth factors, proteases, and components of the extracellular matrix collaboratively interact within the tumor microenvironment, sustaining and driving cancer cell proliferation, invasion, and early metastasis. More recently, the tumor microenvironment has also been appreciated to mediate therapeutic resistance in pancreatic ductal adenocarcinoma, thus opening numerous avenues for novel therapeutic explorations. Inert and soluble components of the tumor stroma have been targeted in order to break down the extracellular matrix scaffold, relieve vessel compression, and increase drug delivery to hypovascular tumors. Moreover, targeting of antiapoptotic, immunosuppressive, and pro-proliferative effects of the tumor stroma provides novel vantage points of attack. This review focuses on current and future developments in pancreatic cancer medicine, with a particular emphasis on biophysical and biochemical approaches that target the tumor microenvironment

Primary Energy Spectrum and Mass Composition Determined with the Tunka EAS Cherenkov Array

New results of 300 hours of operation of the Tunka array are presented. An improved parametrization of the Cherenkov light lateral distribution function (LDF), based on CORSIKA Monte Carlo simulations and the experiment QUEST, has been used for the reconstruction of EAS parameters. The corrected energy spectrum in the knee region is obtained. The mean depth of the EAS maximum has been derived both from the analysis of LDF steepness and the FWHM of Cerenkov light pulse. The mean mass composition around the knee is estimated.Comment: 3 pages, 3 figures, to be published in IJMP