Search results for "mass"
showing 10 items of 9693 documents
Metamorfosis de la prensa de referencia en el contexto digital: clickbait y estrategias de tabloide en Elpais.com
2016
En un contexto marcado por la incertidumbre tecnológica y la búsqueda de un modelo de negocio viable, los medios digitales han sucumbido a diversas estrategias para captar audiencia, reflejada en los clicks que genera cada titular. Este artículo centra la atención en un medio de referencia como El País para analizar qué opciones ha incorporado para atraer visitas a la web. A partir de una metodología cuantitativa y cualitativa, se estudian los contenidos de cuatro secciones que ha sumado Elpais.com en los últimos dos años (SModa, Icon, BuenaVida y Verne), que han logrado generar –en especial la última– un tráfico importante. Las conclusiones del análisis muestran una apuesta por la tabloidi…
L'exemplum di Scipione l'Africano in Sen. dial. XII 12 6: una proposta di esegesi.
2012
The analysis of literary source shows in the exemplum paupertatis of P.Cornelius Scipio Africanus, included by Seneca in Consolatio ad Heluiam matrem, a structure which conforms to a greek rhetorical pattern(commander virtous, but poor, which leaves no dowry to his daughters). In our opinion, Seneca's paternity justifiesthe absence of exemplum into other works prior to Seneca.
Concentration of chromium and nickel in serum of patients with orthopedic implant: An analysis
2021
Introduction: Surgical corrections of fracture using fixation devices made from various alloys (stainless steel, cobalt-chromium alloys, and titanium) carry a risk of these alloys leaching into circulation, potentially causing undesired health effects. Hence, monitoring the levels of metal ions in the serum of postoperative patients with metal implants is mandated. Materials and Methods: Blood samples from seventy patients with orthopedic metal implants was collected after a minimum postoperative period of 1 year. The samples were subjected to triple acid digestion and serum levels of chromium and nickel were analyzed using inductively coupled plasma-mass spectrometry. Results: The concentr…
A new general fragmentation reaction in mass spectrometry: The hydrogen-carbon, carbon-carbon double rearrangement of 2 heteroalkyl substituted diphe…
1995
Diphenylmethyl cations formed by benzylic cleavage of the molecular ions of ortho heteroalkyl substituted 1,1-diphenylalkanes undergo the double rearrangement process (H to C followed by C to C) previously reported for ortho-methoxy derivatives. Hence the formation of substituted benzyl (or tropylium) ions allowing this double rearrangement process constitutes an interesting type of fragmentation reaction characteristic for 1,1-diphenylalkanes bearing ortho substituents (OMe, OEt, OiPr, SMe, NHMe, NMe2) which are able to transfer a hydride to the charged benzyl carbon of diphenylmethyl cations formed by benzylic cleavage of the molecular ion.
Enhanced Heterogeneous Catalytic Conversion of Furfuryl Alcohol into Butyl Levulinate
2014
We study the catalytic condensation of furfuryl alcohol with 1-butanol to butyl levulinate. A screening of several commercial and as-synthesized solid acid catalysts shows that propylsulfonic acid-functionalized mesoporous silica outperforms the state-of-the-art phosphotungstate acid catalysts. The catalyst is prepared via template-assisted sol-gel polycondensation of TEOS and MPTMS. It gives 96 % yield (and 100 % selectivity) of butyl levulinate in 4h at 110 °C. Reaction profiles before and after a hot filtration test confirm that the active catalytic species do not leach into the solution. The catalyst synthesis, characterization, and mode of operation are presented and discussed. Sour ca…
Complexation of Uranium by Cells and S-Layer Sheets of Bacillus sphaericus JG-A12
2005
ABSTRACT Bacillus sphaericus JG-A12 is a natural isolate recovered from a uranium mining waste pile near the town of Johanngeorgenstadt in Saxony, Germany. The cells of this strain are enveloped by a highly ordered crystalline proteinaceous surface layer (S-layer) possessing an ability to bind uranium and other heavy metals. Purified and recrystallized S-layer proteins were shown to be phosphorylated by phosphoprotein-specific staining, inductive coupled plasma mass spectrometry analysis, and a colorimetric method. We used extended X-ray absorption fine-structure (EXAFS) spectroscopy to determine the structural parameters of the uranium complexes formed by purified and recrystallized S-laye…
Effects of NH3 and alkaline metals on the formation of particulate sulfate and nitrate in wintertime Beijing
2020
Sulfate and nitrate from secondary reactions remain as the most abundant inorganic species in atmospheric particle matter (PM). Their formation is initiated by oxidation (either in gas phase or particle phase), followed by neutralization reaction primarily by NH3, or by other alkaline species such as alkaline metal ions if available. The different roles of NH3 and metal ions in neutralizing H2SO4 or HNO3, however, are seldom investigated. Here we conducted semi-continuous measurements of SO4 2−, NO3 −, NH4 +, and their gaseous precursors, as well as alkaline metal ions (Na+, K+, Ca2+, and Mg2+) in wintertime Beijing. Analysis of aerosol acidity (estimated from a thermodynamic model) indicat…
Catalytic Activity of Char Obtained from Fast Pyrolysis in Esterification Reactions
2021
In this study different pathways for obtaining activated carbon with catalytical activity were analysed. Industrially fast pyrolysis is an efficient way of lignocellulosic biomass processing, since in this process various important high value chemicals are obtained. Biochar is obtained as the by-product in fast pyrolysis process from which activated carbon can be acquired with further chemical activation. Different methods for chemical activation of biochar were tested with the obtained activated charcoals being used as a catalyst in esterification reactions to evaluate their potential use as a heterogenic catalyst. Highest catalytical activity was observed when biochar was pre-treated with…
Validation of a method for neutron dosimetry and spectrometry using neutron activation of metal discs
2009
A technique for neutron dosimetry and spectrometry based on neutron activation of different metal discs has been studied. After exposure to a neutron field, the radionuclides produced in the discs are detected using low-level gamma-ray spectrometry and the neutron spectrum is obtained using a spectrum unfolding technique. In order to validate the method, irradiation was performed in a well-characterised (252)Cf neutron reference field. Furthermore, the detector was used to determine the neutron fluence rate and spectrum at a storage place for MOX nuclear fuel. The results of the two measurements are reported and discussed.
P056 Occupational exposure to metals and risk of breast, chronic lymphocytic leukaemia, colorectal, prostate, and stomach cancer in the MCC-spain cas…
2016
Arsenic, cadmium, chromium, and nickel are classified by IARC as human carcinogens (Group 1), while lead as a probable/possible carcinogen to humans (Group 2A). We explored associations between occupational exposure to metals and breast, chronic lymphocytic leukaemia (CLL), colorectal, prostate, and stomach cancer in the MCC-Spain population based case-control study. Methods The analyses were based on 3047 controls, and 1499 breast, 1539 colorectal, 332 CLL, 1070 prostate, and 382 stomach cancer cases. Occupational exposure to arsenic, cadmium, chromium, iron, lead and nickel was assessed using the MatEmEsp job-exposure matrix. Logistic regression models accounting for education, sex, geogr…