The Swift X-ray Telescope Cluster Survey II. X-ray spectral analysis

(Abridged) We present a spectral analysis of a new, flux-limited sample of 72 X-ray selected clusters of galaxies identified with the X-ray Telescope (XRT) on board the Swift satellite down to a flux limit of ~10-14 erg/s/cm2 (SWXCS, Tundo et al. 2012). We carry out a detailed X-ray spectral analysis with the twofold aim of measuring redshifts and characterizing the properties of the Intra-Cluster Medium (ICM). Optical counterparts and spectroscopic or photometric redshifts are obtained with a cross-correlation with NED. Additional photometric redshifts are computed with a dedicated follow-up program with the TNG and a cross-correlation with the SDSS. We also detect the iron emission lines in 35% of the sample, and hence obtain a robust measure of the X-ray redshift zX. We use zX whenever the optical redshift is not available. Finally, for all the sources with measured redshift, background-subtracted spectra are fitted with a mekal model. We perform extensive spectral simulations to derive an empirical formula to account for fitting bias. The bias-corrected values are then used to investigate the scaling properties of the X-ray observables. Overall, we are able to characterize the ICM of 46 sources. The sample is mostly constituted by clusters with temperatures between 3 and 10 keV, plus 14 low-mass clusters and groups with temperatures below 3 keV. The redshift distribution peaks around z~0.25 and extends up to z~1, with 60% of the sample at 0.1<z<0.4. We derive the Luminosity-Temperature relation for these 46 sources, finding good agreement with previous studies. The quality of the SWXCS sample is comparable to other samples available in the literature and obtained with much larger X-ray telescopes. Our results have interesting implications for the design of future X-ray survey telescopes, characterised by good-quality PSF over the entire field of view and low background.Comment: 27 pages, 15 figures; minor typos corrected. To be published in A&A, Volume 567, July 2014. Websites of the SWXCS project: http://www.arcetri.astro.it/SWXCS/ and http://swxcs.ustc.edu.cn

Chlorine-free synthesis: An overview

Since the Industrial Revolution, chlorine has featured as an iconic molecule in process chemistry even though its production by electrolysis of sodium chloride is very energy-intensive. Owing to its high energy and reactivity, chlorine allows the manufacture of chlorinated derivatives in a very easy way: AlCl3, SnCl4, TiCl4, SiCl4, ZnCl2, PCl3, PCl5, POCl3, COCl2, etc. in turn are pillar intermediates in the production of numerous everyday goods. This kind of chloride chemistry is widely used because the energy is transferred to these intermediates, making further syntheses easy. The environmental and health constraints (toxicity and eco-toxicity, ozone layer depletion) and the growing need for energy (energy efficiency, climate change) force us to take advantage from available knowledge to develop new chemical strategies. Substitution of chlorine in end products in compounds where "chlorine is used in the making" means that we avoid electrolysis as primary energetic source; this makes chemistry "without chlorine" considerably more difficult and illustrates why it has not found favor in the past. The rationale behind this Special Topic issue is to seek useful and industrially relevant examples for alternatives to chlorine in synthesis, so as to facilitate the development of industrially relevant and implementable breakthrough technologies

Selective monomethylation reactions of methylene-active compounds with dimethylcarbonate. An example of clean synthesis

Dimethylcarbonate (DMC), an environmentally friendly substitute for dimethylsulfate and methyl halides in methylation reactions, is also a very selective reagent. Under batch conditions, with potassium carbonate as the catalyst, the reactions of DMC, used as the solvent of the reactions, with methylene-active compounds (arylacetonitriles and arylacetoesters, aroxyacetonitriles and methyl aroxyacetates, benzylaryl- and alkylaryl-sulfones) produce monomethylated derivatives, with a selectivity not previously observed (i.e., >99%). These are examples of "green chemistry"

New developments in dimethyl carbonate chemistry

Dimethylcarbonate (DMC) is a valuable methylating reagent which can replace methyl halides and dimethylsulfate in the methylation of a variety of nucleophiles. It couples tunable reactivity and unprecedented selectivity toward mono-C- and mono-N-methylation in the reactions of acidic CH2 and primary aromatic amines, respectively. In addition, it is a prototype example of a green reagent, since it is nontoxic, made by a clean process, and biodegradable, and it reacts in the presence of a catalytic amount of base thereby avoiding the formation of undesirable inorganic salts as by-products. Other remarkable reactions are those where DMC behaves as an oxidant: cyclic ketones are transformed into alpha,omega -dimethyl esters with a reaction of atom efficiency of 1.0

Low serum phosphate levels are related to increased cardiovascular risk in HIV-1 infected patients

Purpose of the study Hypophosphatemia may contribute directly to the devel- opment of obesity, hypertension and dyslipidemia. Hyperglycemia, insulin resistance, hyperlipidemia and hypertension, which are components of metabolic syn- drome, are also recognized as strong risk factors for car- diovascular disease [1]. This study was performed to determine whether serum phosphate levels are asso- ciated with increased risk for cardiovascular events. Methods We enrolled 125 consecutive HIV-1-infected patients in a cross-sectional study. All patients were receiving highly active antiretroviral therapy (HAART) for more than six months. Fasting phosphate, lipids (cholesterol, HDL, triglycerides), Homeostasis Model Assessment (HOMA), blood pressure were evaluated. Framingham 10 years risk of general cardiovascular disease was used to assess three cardiovascular risk (CVR) categories (low CVR 20%). Summary of results We observed a statistically significant decrease in serum phosphate levels in the three different CVR groups (low risk: 3.5 mg/dl; medium risk: 3.3 mg/dl; high risk: 2.9 mg/dl; p=0.001). There was a strong negative correlation between Framingham score and phosphate levels (r:- 0.37, p<0.0001). Figure 1 Multiple regression analysis, including age, months of HAART, CD4 cells count, cholesterol, HDL, HOMA, systolic pressure, months of Tenofovir use, showed that only HOMA (r:-0.30, p<0.01) and age (r:-0.3, p<0.01) were the most important determinants of serum phos- phate values. Conclusions We found that lower phosphate level is correlated with cardiovascular risk and insulin resistance. Therefore, when serum phosphate levels are too low the patients is at risk for cardiovascular events and/or metabolic syndrome

Low Energy STEM of Multi-Layers and Dopant Profiles

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