Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 88
Filtrar
Más filtros

Intervalo de año de publicación
1.
Sensors (Basel) ; 23(3)2023 Feb 03.
Artículo en Inglés | MEDLINE | ID: mdl-36772780

RESUMEN

The olive tree is an important crop in Portugal, where different levels of intensification coexist. The traditional olive orchards present profitability problems, mainly due to harvesting, so there has been a drastic reconversion towards high-density or super-high-density olive orchards. The latter present major constraints due to very specific needs for their use, being practically destined for new orchards. Consequently, the possibility of using systems based on canopy shakers in high-density olive orchards with local varieties is promising. The objective of this work is to evaluate a prototype canopy shaker for the harvesting of high-density olive orchards of the Portuguese variety 'Cobrançosa'. The evaluation is based on the study of canopy shaking in order to adapt canopy training and the adaptability of the machine. For this purpose, the vibration of 72 points of the tree canopy was recorded and a qualitative assessment of the harvest was carried out. Differences were found between the different zones according to the direction of the forward movement of the harvester and the distance to the trunk. These differences were associated with the values obtained for fruit detachment, and a greater quantity of fruit was harvested in the areas of the canopy in contact with the rods.


Asunto(s)
Olea , Portugal , Frutas
2.
Org Biomol Chem ; 20(5): 1008-1012, 2022 02 02.
Artículo en Inglés | MEDLINE | ID: mdl-34985090

RESUMEN

The 1,3-diethoxycarbonyl-2,4,5-trimethylcyclopentadienyl (CpE) rhodium(III) complex displayed high efficacy in the catalytic oxidative annulation of 1-naphthols with internal alkynes under mild conditions. DFT calculations revealed that lower activation energies for the concerted metalation-deprotonation and the reductive elimination steps are the key to improved reactivity.

3.
Nature ; 533(7604): 521-6, 2016 05 26.
Artículo en Inglés | MEDLINE | ID: mdl-27225125

RESUMEN

Atmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood. Globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours. It is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere, and that ions have a relatively minor role. Some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded. Here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. The highly oxygenated molecules (HOMs) are produced by ozonolysis of α-pinene. We find that ions from Galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. Our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative HOMs. Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution.


Asunto(s)
Aerosoles/química , Atmósfera/química , Cambio Climático , Iones/química , Oxígeno/química , Material Particulado/química , Contaminación del Aire/análisis , Monoterpenos Bicíclicos , Radiación Cósmica , Actividades Humanas , Monoterpenos/química , Oxidación-Reducción , Ozono/química , Tamaño de la Partícula , Teoría Cuántica , Ácidos Sulfúricos/análisis , Volatilización
4.
Nature ; 533(7604): 527-31, 2016 05 26.
Artículo en Inglés | MEDLINE | ID: mdl-27225126

RESUMEN

About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday. Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres. In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles, thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth, leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer. Although recent studies predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon, and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Köhler theory), has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10(-4.5) micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10(-4.5) to 10(-0.5) micrograms per cubic metre). We present a particle growth model that quantitatively reproduces our measurements. Furthermore, we implement a parameterization of the first steps of growth in a global aerosol model and find that concentrations of atmospheric cloud concentration nuclei can change substantially in response, that is, by up to 50 per cent in comparison with previously assumed growth rate parameterizations.

5.
J Am Chem Soc ; 143(30): 11325-11331, 2021 08 04.
Artículo en Inglés | MEDLINE | ID: mdl-34283597

RESUMEN

Photoinduced in situ "oxidation" of half-sandwich metal complexes to "high-valent" cationic metal complexes has been used to accelerate catalytic reactions. Here, we report the unprecedented photoinduced in situ "reduction" of half-sandwich metal [Rh(III)] complexes to "low-valent" anionic metal [Rh(II)] ate complexes, which facilitate ligand exchange with electron-deficient elements (diboron). This strategy was realized by using a functionalized cyclopentadienyl (CpA3) Rh(III) catalyst we developed, which enabled the basic group-directed room temperature ortho-C-H borylation of arenes.

6.
Proc Natl Acad Sci U S A ; 115(37): 9122-9127, 2018 09 11.
Artículo en Inglés | MEDLINE | ID: mdl-30154167

RESUMEN

Nucleation and growth of aerosol particles from atmospheric vapors constitutes a major source of global cloud condensation nuclei (CCN). The fraction of newly formed particles that reaches CCN sizes is highly sensitive to particle growth rates, especially for particle sizes <10 nm, where coagulation losses to larger aerosol particles are greatest. Recent results show that some oxidation products from biogenic volatile organic compounds are major contributors to particle formation and initial growth. However, whether oxidized organics contribute to particle growth over the broad span of tropospheric temperatures remains an open question, and quantitative mass balance for organic growth has yet to be demonstrated at any temperature. Here, in experiments performed under atmospheric conditions in the Cosmics Leaving Outdoor Droplets (CLOUD) chamber at the European Organization for Nuclear Research (CERN), we show that rapid growth of organic particles occurs over the range from [Formula: see text]C to [Formula: see text]C. The lower extent of autoxidation at reduced temperatures is compensated by the decreased volatility of all oxidized molecules. This is confirmed by particle-phase composition measurements, showing enhanced uptake of relatively less oxygenated products at cold temperatures. We can reproduce the measured growth rates using an aerosol growth model based entirely on the experimentally measured gas-phase spectra of oxidized organic molecules obtained from two complementary mass spectrometers. We show that the growth rates are sensitive to particle curvature, explaining widespread atmospheric observations that particle growth rates increase in the single-digit-nanometer size range. Our results demonstrate that organic vapors can contribute to particle growth over a wide range of tropospheric temperatures from molecular cluster sizes onward.

7.
Clin Oral Investig ; 25(5): 2727-2735, 2021 May.
Artículo en Inglés | MEDLINE | ID: mdl-32974775

RESUMEN

OBJECTIVES: Limited long-term data are available when comparing the esthetic outcomes of coronally advanced flap (CAF) with or without a connective tissue graft (CTG). The aim of this study was to compare the 4-year esthetic outcomes of CAF vs CAF + CTG for the treatment of isolated maxillary gingival recessions. MATERIAL AND METHODS: Forty-eight patients were randomly assigned for treatment either with CAF (control; N = 24) or to CAF + CTG (test group; N = 24). Patients were followed after the surgery until the final evaluation. A professional esthetic evaluation was performed using the Root coverage Esthetic Score (RES). Recession reduction, mean root coverage, and complete root coverage were also evaluated. RESULTS: Forty-two patients completed the study at the 4-year recall. A significant recession reduction was evident at 4 years, without significant intergroup differences. The CAF group showed a statistically significant higher final RES compared with the CAF + CTG group (9.14 ± 1.08 vs 7.25 ± 1.29, respectively, p < 0.001). Regarding the individual components of RES, gingival margin and marginal tissue contour were significantly higher in the CAF group compared with that in the CAF + CTG group. CONCLUSIONS: CAF presented with a significantly higher overall esthetic score than CAF + CTG, and in the individual RES components of marginal tissue contour and gingival margin after 4 years. CLINICAL RELEVANCE: CAF without the addition of CTG provided higher esthetic outcomes for the treatment of isolated gingival recessions.


Asunto(s)
Recesión Gingival , Tejido Conectivo , Estética Dental , Estudios de Seguimiento , Encía , Recesión Gingival/cirugía , Humanos , Pérdida de la Inserción Periodontal , Raíz del Diente , Resultado del Tratamiento
8.
Adv Mind Body Med ; 35(3): 10-19, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34237025

RESUMEN

CONTEXT: Students are vulnerable to developing anxiety, a psychiatric disorder closely related to emotional stress, when systematically stressed by classes, homework, and evaluations. Qigong integrates physical, respiratory, and mental exercises, inducing vegetative biofeedback with significant effects on physiological regulation. OBJECTIVE: The current study aimed to assess the potential effects of specific Qigong exercises on students' anxiety levels and evaluate the feasibility of practical integration in a daily school context. DESIGN: The research team developed a randomized controlled trial. SETTING: This study was performed in Cedros and Horizonte private schools located in Vila Nova de Gaia in Portugal. PARTICIPANTS: Participants were 104 high-school students at the schools. INTERVENTION: Participants were randomly divided into three groups: (1) an intervention group, the Qigong (QG) group (n = 34), which performed Qigong exercises; (2) a control group, the TV documentary (TVD) group (n = 34), which watched a TV documentary; and (3) a second control group, the typical school duties (TSD) group (n = 36), which performed regular school duties. OUTCOME MEASURES: Anxiety levels were assessed through a psychological test, the State-Trait Anxiety Inventory (STAI) and salivary cortisol tests. RESULTS: Psychological and biochemical variables assessed at baseline and postintervention showed a greater decrease in anxiety levels in the QG group than in the other two groups. CONCLUSIONS: Qigong seems to be an efficient tool to reduce anxiety and control the stress of high-school students.


Asunto(s)
Qigong , Adolescente , Ansiedad/terapia , Humanos , Portugal , Instituciones Académicas , Estudiantes
9.
Waste Manag Res ; 39(1): 93-100, 2021 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-33208056

RESUMEN

The investigation of the views of the stakeholders involved in the municipal solid waste separate collection programme (CP) performed in the East Zone of the city of São Paulo is presented in this paper. Aiming to obtain the necessary information to be analysed, interviews with the manager of the Municipal Urban Cleaning Authority (MUCA) of the city, with leaders of recycling worker cooperatives (WCs), and citizens were performed using semi-structured questionnaires. The analysis was performed using the software "IRAMUTEQ". The results show that, in the view of the manager of the MUCA of the city and the WCs' leaders, the low adhesion of the population to the separate CP is the greatest obstacle to a further expansion of the existing programme. At the same time, the citizens have blamed the low diffusion made by the municipality about the separate CP in the East Zone of São Paulo. Thus, it can be concluded that the separate CP available in the East Zone of São Paulo is still flawed; since neither the public power, the WCs, nor the population are satisfied and point out several flaws. This situation highlights the need to establish better venues for discussion between the population, WCs, and the municipality to jointly design a separate collection system with a more participatory approach.


Asunto(s)
Reciclaje , Administración de Residuos , Brasil , Ciudades , Residuos Sólidos
10.
Inter Econ ; 56(3): 167-173, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34103762

RESUMEN

Multinational companies are now obliged to deliver an annual report to the tax authorities with information disaggregated by country (country-by-country reporting) in order to show where the assets and workers are allocated, how profits are distributed and to whom taxes are paid. Unfortunately, these reports are not made public in the European Union, thus preventing public scrutiny about the strategies used by multinational companies to displace profits to tax havens. This article applies the Unitary Taxation regime proposed by the European Commission to US multinational companies. The results confirm a strong bias among the profits distribution towards countries with lower corporate tax rates. Likewise, they confirm the capacity of the Unitary Taxation to promote a fairer distribution of tax revenues. These results can be a good contribution to the current Portuguese presidency of the European Union, which managed to gather important support to move forward with the European public country-by-country reporting directive.

11.
Environ Sci Technol ; 54(13): 7911-7921, 2020 07 07.
Artículo en Inglés | MEDLINE | ID: mdl-32515954

RESUMEN

To better understand the role of aromatic hydrocarbons in new-particle formation, we measured the particle-phase abundance and volatility of oxidation products following the reaction of aromatic hydrocarbons with OH radicals. For this we used thermal desorption in an iodide-adduct Time-of-Flight Chemical-Ionization Mass Spectrometer equipped with a Filter Inlet for Gases and AEROsols (FIGAERO-ToF-CIMS). The particle-phase volatility measurements confirm that oxidation products of toluene and naphthalene can contribute to the initial growth of newly formed particles. Toluene-derived (C7) oxidation products have a similar volatility distribution to that of α-pinene-derived (C10) oxidation products, while naphthalene-derived (C10) oxidation products are much less volatile than those from toluene or α-pinene; they are thus stronger contributors to growth. Rapid progression through multiple generations of oxidation is more pronounced in toluene and naphthalene than in α-pinene, resulting in more oxidation but also favoring functional groups with much lower volatility per added oxygen atom, such as hydroxyl and carboxylic groups instead of hydroperoxide groups. Under conditions typical of polluted urban settings, naphthalene may well contribute to nucleation and the growth of the smallest particles, whereas the more abundant alkyl benzenes may overtake naphthalene once the particles have grown beyond the point where the Kelvin effect strongly influences the condensation driving force.


Asunto(s)
Hidrocarburos Aromáticos , Compuestos Orgánicos Volátiles , Aerosoles , Gases , Volatilización
12.
Waste Manag Res ; 38(12): 1321-1330, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-32414305

RESUMEN

Construction and demolition wastes have been studied by technical means aiming at the development of management tools to reduce their environmental impacts. Among these, recycling can be highlighted. This paper aims at the technical assessment of basket gabions filled with construction and demolition solid waste. Gabions are usually used for retaining walls construction, and these are commonly filled with rocks. Retaining walls are essential for earthfill slopes stabilization, and they must have proper characteristics of strength. However, depending on the slope height or the technical responsibility of the retaining wall, alternative materials with proper characteristics could be used to fill the gabions. The use of recycled material for gabion filling could reduce environmental impacts and costs caused by retaining wall construction. So, basket gabion cells were filled with construction solid waste and basaltic rocks, both crushed into coarse granulometry aiming to compare technical characteristics among them. The performed laboratory tests showed that the horizontal and vertical displacements determined for gabion filled with wastes were near to those obtained for gabions filled with basaltic rocks for a retaining wall of 5 m and up. In conclusion, it can be drawn that basket gabions filled with construction and demolition waste may be a technical alternative for civil construction, reducing environmental impacts and raw material consumption for retaining wall execution.


Asunto(s)
Industria de la Construcción , Administración de Residuos , Materiales de Construcción , Ambiente , Residuos Industriales , Reciclaje , Residuos Sólidos
13.
Environ Sci Technol ; 53(21): 12357-12365, 2019 Nov 05.
Artículo en Inglés | MEDLINE | ID: mdl-31553886

RESUMEN

We use a real-time temperature-programmed desorption chemical-ionization mass spectrometer (FIGAERO-CIMS) to measure particle-phase composition and volatility of nucleated particles, studying pure α-pinene oxidation over a wide temperature range (-50 °C to +25 °C) in the CLOUD chamber at CERN. Highly oxygenated organic molecules are much more abundant in particles formed at higher temperatures, shifting the compounds toward higher O/C and lower intrinsic (300 K) volatility. We find that pure biogenic nucleation and growth depends only weakly on temperature. This is because the positive temperature dependence of degree of oxidation (and polarity) and the negative temperature dependence of volatility counteract each other. Unlike prior work that relied on estimated volatility, we directly measure volatility via calibrated temperature-programmed desorption. Our particle-phase measurements are consistent with gas-phase results and indicate that during new-particle formation from α-pinene oxidation, gas-phase chemistry directly determines the properties of materials in the condensed phase. We now have consistency between measured gas-phase product concentrations, product volatility, measured and modeled growth rates, and the particle composition over most temperatures found in the troposphere.


Asunto(s)
Contaminantes Atmosféricos , Ozono , Aerosoles , Monoterpenos Bicíclicos , Monoterpenos , Volatilización
14.
Proc Natl Acad Sci U S A ; 113(43): 12053-12058, 2016 10 25.
Artículo en Inglés | MEDLINE | ID: mdl-27790989

RESUMEN

The magnitude of aerosol radiative forcing caused by anthropogenic emissions depends on the baseline state of the atmosphere under pristine preindustrial conditions. Measurements show that particle formation in atmospheric conditions can occur solely from biogenic vapors. Here, we evaluate the potential effect of this source of particles on preindustrial cloud condensation nuclei (CCN) concentrations and aerosol-cloud radiative forcing over the industrial period. Model simulations show that the pure biogenic particle formation mechanism has a much larger relative effect on CCN concentrations in the preindustrial atmosphere than in the present atmosphere because of the lower aerosol concentrations. Consequently, preindustrial cloud albedo is increased more than under present day conditions, and therefore the cooling forcing of anthropogenic aerosols is reduced. The mechanism increases CCN concentrations by 20-100% over a large fraction of the preindustrial lower atmosphere, and the magnitude of annual global mean radiative forcing caused by changes of cloud albedo since 1750 is reduced by [Formula: see text] (27%) to [Formula: see text] Model uncertainties, relatively slow formation rates, and limited available ambient measurements make it difficult to establish the significance of a mechanism that has its dominant effect under preindustrial conditions. Our simulations predict more particle formation in the Amazon than is observed. However, the first observation of pure organic nucleation has now been reported for the free troposphere. Given the potentially significant effect on anthropogenic forcing, effort should be made to better understand such naturally driven aerosol processes.


Asunto(s)
Aerosoles/análisis , Atmósfera/análisis , Modelos Estadísticos , Aerosoles/química , Contaminantes Atmosféricos/análisis , Contaminantes Atmosféricos/química , Atmósfera/química , Clima , Simulación por Computador , Historia del Siglo XVIII , Historia del Siglo XIX , Historia del Siglo XX , Historia del Siglo XXI , Humanos , Desarrollo Industrial/historia , Incertidumbre
15.
Rheumatology (Oxford) ; 56(7): 1189-1199, 2017 07 01.
Artículo en Inglés | MEDLINE | ID: mdl-28398504

RESUMEN

Objectives: To assess the prevalences across Europe of radiological indices of degenerative inter-vertebral disc disease (DDD); and to quantify their associations with, age, sex, physical anthropometry, areal BMD (aBMD) and change in aBMD with time. Methods: In the population-based European Prospective Osteoporosis Study, 27 age-stratified samples of men and women from across the continent aged 50+ years had standardized lateral radiographs of the lumbar and thoracic spine to evaluate the severity of DDD, using the Kellgren-Lawrence (KL) scale. Measurements of anterior, mid-body and posterior vertebral heights on all assessed vertebrae from T4 to L4 were used to generate indices of end-plate curvature. Results: Images from 10 132 participants (56% female, mean age 63.9 years) passed quality checks. Overall, 47% of men and women had DDD grade 3 or more in the lumbar spine and 36% in both thoracic and lumbar spine. Risk ratios for DDD grades 3 and 4, adjusted for age and anthropometric determinants, varied across a three-fold range between centres, yet prevalences were highly correlated in men and women. DDD was associated with flattened, non-ovoid inter-vertebral disc spaces. KL grade 4 and loss of inter-vertebral disc space were associated with higher spine aBMD. Conclusion: KL grades 3 and 4 are often used clinically to categorize radiological DDD. Highly variable European prevalences of radiologically defined DDD grades 3+ along with the large effects of age may have growing and geographically unequal health and economic impacts as the population ages. These data encourage further studies of potential genetic and environmental causes.


Asunto(s)
Degeneración del Disco Intervertebral/diagnóstico por imagen , Degeneración del Disco Intervertebral/epidemiología , Osteocondrosis/diagnóstico por imagen , Osteocondrosis/epidemiología , Osteoporosis/diagnóstico por imagen , Distribución por Edad , Anciano , Densidad Ósea , Estudios de Cohortes , Europa (Continente) , Femenino , Humanos , Masculino , Persona de Mediana Edad , Prevalencia , Estudios Prospectivos , Radiografía/métodos , Reproducibilidad de los Resultados , Índice de Severidad de la Enfermedad , Distribución por Sexo
17.
J Phys Chem A ; 120(27): 5220-9, 2016 Jul 14.
Artículo en Inglés | MEDLINE | ID: mdl-27045948

RESUMEN

In this work, hydrogen peroxide has been studied with threshold photoelectron (TPE) spectroscopy and photoelectron (PE) spectroscopy. The TPE spectrum has been recorded in the 10.0-21.0 eV ionization energy region, and the PE spectrum has been recorded at 21.22 eV photon energy. Five bands have been observed which have been assigned on the basis of UCCSD(T)-F12/VQZ-F12 and IP-EOM CCSD calculations. Vibrational structure has only been resolved in the TPE spectrum of the first band, associated with the X̃(2)Bg H2O2(+) ← X̃(1)A H2O2 ionization, on its low energy side. This structure is assigned with the help of harmonic Franck-Condon factor calculations that use the UCCSD(T)-F12a/VQZ-F12 computed adiabatic ionization energy (AIE), and UCCSD(T)-F12a/VQZ-F12 computed equilibrium geometric parameters and harmonic vibrational frequencies for the H2O2 X̃(1)A state and the H2O2(+) X̃(2)Bg state. These calculations show that the main vibrational structure on the leading edge of the first TPE band is in the O-O stretching mode (ω3) and the HOOH deformation mode (ω4), and comparison of the simulated spectrum to the experimental spectrum gives the first AIE of H2O2 as (10.685 ± 0.005) eV and ω4 = (850 ± 30) and ω3 = (1340 ± 30) cm(-1) in the X̃(2)Bg state of H2O2(+). Contributions from ionization of vibrationally excited levels in the torsion mode have been identified in the TPE spectrum of the first band and the need for a vibrationally resolved TPE spectrum from vibrationally cooled molecules, as well as higher level Franck-Condon factors than performed in this work, is emphasized.

18.
BMC Gastroenterol ; 15: 105, 2015 Aug 19.
Artículo en Inglés | MEDLINE | ID: mdl-26285593

RESUMEN

BACKGROUND: Biliary leaks have been treated with endoscopic management using different techniques with conflicting results. Furthermore the appropriate rescue therapy for refractory leaks has not been established. We evaluated the clinical effectiveness of initial endotherapy for postcholecystectomy biliary leaks using an homogenous approach (sphincterotomy + placement of a 10-French plastic stent) in a large series of patients as well as the optimal and efficacy of rescue endotherapy for refractory biliary leaks. METHODS: This was a multicenter, retrospective study of 178 patients who underwent endoscopic management of postcholecystectomy biliary leaks with a combination of biliary sphincterotomy and the placement of a large-bore (10-French) plastic stent. Data were collected to analyze the clinical outcomes and technical success, efficacy of the rescue endotherapy and the need for surgery, adverse events and prognostic factors for clinical success of endotherapy. RESULTS: Following endotherapy, closure of the leak was accomplished in 162/178 patients (91.0%). The multivariate logistic model showed that the type of leak, namely a high-grade biliary leak, was the only independent prognostic factor associated with treatment failure (OR = 26.78; 95% CI = 6.59-108.83; P < 0.01). The remaining 16 patients were treated with multiple plastic stents (MPSs) with a success rate of 62.5% (10 patients). The use of fewer than 3 plastic stents (P = 0.023) and a high-grade biliary leak (P = 0.034) were shown to be significant predictors of treatment failure with MPSs in refractory bile leaks. The 6 patients in whom the placement of MPSs failed were retreated with a fully cover self-expandable metallic stent (FCSEMS), resulting in closure of the leak in all cases. CONCLUSIONS: Endotherapy of biliary leaks with a combination of biliary sphincterotomy and the placement of a large-bore plastic stent is associated with a high rate of success (90%). However in our series there were several failures using MPSs as a strategy for rescue endotherapy suggesting that refractory biliary leaks should be treated with FCSEMS especially in patients with high-grade leaks.


Asunto(s)
Conductos Biliares/lesiones , Colangiopancreatografia Retrógrada Endoscópica , Colecistectomía Laparoscópica/efectos adversos , Esfinterotomía Endoscópica , Stents , Adulto , Anciano , Anciano de 80 o más Años , Colangiopancreatografia Retrógrada Endoscópica/efectos adversos , Femenino , Humanos , Modelos Logísticos , Masculino , Persona de Mediana Edad , Reoperación , Estudios Retrospectivos , Stents Metálicos Autoexpandibles , Stents/efectos adversos , Resultado del Tratamiento , Heridas y Lesiones/cirugía , Adulto Joven
19.
J Phys Chem A ; 119(18): 4118-26, 2015 May 07.
Artículo en Inglés | MEDLINE | ID: mdl-25898938

RESUMEN

We study the gas-phase pyrolysis of benzyl azide (BA, C6H5CH2N3) using ultraviolet photoelectron spectroscopy (UVPES) and matrix-isolation infrared (IR) spectroscopy, together with electronic structure calculations and Rice-Ramsperger-Kassel-Marcus (RRKM) calculations. It is found that BA decomposes via N2 elimination at ca. 615 K, primarily yielding benzenemethaninime. Other end products include HCN and C6H6. N-Methyleneaniline is not detected, although its formation at higher temperature is foreseen by RRKM calculations.

20.
Dig Dis Sci ; 59(11): 2779-89, 2014 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-24821464

RESUMEN

BACKGROUND: Self-expandable metal stents (SEMSs) can be used for palliation of combined malignant biliary and duodenal obstructions. However, the results of the concomitant stent placement for the duration of the patients' lives, as well as the need for and efficacy of endoscopic revision, are unclear. AIM: This study evaluated the clinical effectiveness of SEMS placement for combined biliary and duodenal obstructions throughout the patients' lives and the need for endoscopic revision. METHODS: This study is a retrospective multicenter study of 50 consecutive patients who underwent simultaneous or sequential SEMS placement for malignant biliary and duodenal obstructions. The data were collected to analyze the sustained relief of obstructive symptoms until the patients' death and the efficacy of endoscopic revision, as well as stent patency, adverse events, survival and prognostic factors for stent patency. RESULTS: Technical and immediate clinical success was achieved in all of the patients. Duodenal stricture occurred before the papilla in 35 patients (70 %), involved the papilla in 11 patients (22 %) and was observed distal to the papilla in four patients (8 %). Initial biliary stenting was performed endoscopically in 42 patients (84 %) and percutaneously in eight patients. After combined stenting, 30 patients (60 %) required no additional intervention until the time of their death. The remaining 20 patients were successfully treated using endoscopic stent reinsertion: nine patients needed biliary revision, three patients needed duodenal restenting and eight patients needed both biliary and duodenal reinsertion. The median duodenal stent patency and median biliary stent patency were 34 and 27 weeks, respectively. The median survival after combined stent placement was 18 weeks. A Cox multivariate analysis showed that duodenal stent obstruction after combined stenting was a risk factor for biliary stent obstruction (hazard ratio 6.85; 95 % confidence interval 1.43-198.98; P = 0.025). CONCLUSIONS: Endoscopic bilio-duodenal bypass is clinically effective, and the majority of the patients need no additional intervention until their death. Endoscopic revision is feasible and has a high success rate.


Asunto(s)
Procedimientos Quirúrgicos del Sistema Biliar/métodos , Colestasis/patología , Obstrucción Duodenal/patología , Duodeno/cirugía , Stents , Adolescente , Anciano , Anciano de 80 o más Años , Colestasis/cirugía , Obstrucción Duodenal/cirugía , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Resultado del Tratamiento
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA