Optimización del proceso kraft en maderas de Eucalyptus globulus

Se ha estudiado en maderas de E. globulus como afecta el factor H y la carga de álcali activo en cocción sobre la facilidad de la deslignificación, el contenido en carbohidratos y la eliminación de extractos de las pastas crudas obtenidas a un mismo nivel de lignina residual. Los resultados obtenidos mostraron que trabajar con bajas cargas de álcali activo y temperaturas en cocción más elevadas, aumenta el rendimiento de pasta en cocción y eliminan más sitosterol. Sin embargo, las blancuras más altas se obtienen trabajando con alta carga de álcali activo. Los xilanos son los compuestos más sensibles a la alta carga de álcali y se eliminan en gran extensión. Las pastas obtenidas con bajo álcali residual en cocción tienen mejor estallido y tracción pero peor drenabilidad, volumen, opacidad y porosidad.___________________________________This paper studies how H factor and active alkali loads in cooking affect E. globulus woods with regard to ease of delignification, carbohydrate content or removal of extractives. The results obtained demonstrated that working with low alkali loads and higher cooking temperatures increase pulp production and remove greater amounts of sitosterol. However, the greatest brightness is achieved by working with a high active alkali load. Xylans are the most sensitive compounds to high alkali loads and to a large extent are removed. Pulp produced with low residual alkali in the cooking stage has better burst index and tensile strength, but lower dewatering, bulk, opacity and air permeability

Trauma Exposure Among Women in the Pacific Rim

Purpose Healthcare professionals who provide services in the immediate or long‐term aftermath of traumatic events need to understand the nature and frequency of traumatic events in the lives of women. However, research on trauma exposure in women has only recently begun to assess events other than intimate partner and sexual violence and has not supported direct statistical comparison of cross‐national and cross‐cultural data. The purpose of this descriptive, correlational study was to describe and compare trauma exposure prevalence and type in community‐based samples of women in the United States, Colombia, and Hong Kong. Design Women were recruited through posted notices at community health sites, snowball sampling, and online advertisements (N = 576). The Life Stressor Checklist‐Revised (total score range 0 to 30) was used to determine the type and prevalence of trauma exposure. Data were collected by native language members of the research team. Methods Descriptive statistics were used to summarize demographic characteristics and trauma exposure for the total sample and each community‐based sample (location). Between‐location differences were tested using Fisher\u27s exact tests for categorical measures and general linear models with pairwise a posteriori least squares t‐test for continuous measures. Responses to open‐ended questions were translated and categorized. Findings Over 99% of women in the total sample reported at least one traumatic life event. The mean number of traumatic life events per participant was 7, ranging from 0 to 24. Although there was consistency in the most commonly reported trauma exposures across locations, the rates of specific events often differed. Conclusions Historical, political, geographic, and cultural factors may explain differences in trauma exposure among women in the four locations studied. Clinical Relevance This study offers relevant knowledge for providers in diverse locations who provide services to women who have experienced traumatic events and provides evidence for the need for future research to further enhance knowledge of trauma exposure among women, and on the effects of trauma in women\u27s lives

Leasing o arrendamiento financiero

Tesis (Economista).--Universidad de Cartagena. Facultad de Ciencias Económicas. Programa de Economía, 1983.El presente estudio tiene por objeto determinar que es realmente esta modalidad de recursos financieros y la incidencia que esta pueda tener en la reactivacion del sector productivo

First eddy covariance flux measurements of semi-volatile organic compounds with the PTR3-TOF-MS

We present first eddy covariance flux measurements with the PTR3-TOF-MS, a novel proton transfer time of flight reaction mass spectrometer. During 3 weeks in spring 2016, the instrument recorded 10 Hz data of biogenic volatile organic compounds above a boreal forest, on top of a measurement tower at the SMEAR (Station for Measuring Ecosystem -Atmosphere Relations) II station in Hyytiala, Finland. Flux and concentration data of isoprene, monoterpenes, and sesquiterpenes were compared to the literature. Due to the improved instrument sensitivity and a customized wall-less inlet design, we could detect fluxes of semi-volatile and low-volatility organic compounds with less than singledigit picomol per square meter per second (pmolm(-2) s(-1)) values for the first time. These compounds include sesquiterpene oxidation products and diterpenes. Daytime diterpene fluxes were in the range of 0.05 to 0.15 pmolm(-2) s(-1), which amounts to about 0.25% to 0.5% of the daytime sesquiterpene flux above canopy.Peer reviewe

Plant surface reactions: an opportunistic ozone defence mechanism impacting atmospheric chemistry

Elevated tropospheric ozone concentrations are considered a toxic threat to plants, responsible for global crop losses with associated economic costs of several billion dollars per year. Plant injuries have been linked to the uptake of ozone through stomatal pores and oxidative damage of the internal leaf tissue. But a striking question remains: can surface reactions limit the stomatal uptake of ozone and therefore reduce its detrimental effects to plants? In this laboratory study we could show that semi-volatile organic compounds exuded by the glandular trichomes of different Nicotiana tabacum varieties are an efficient ozone sink at the plant surface. In our experiments, different diterpenoid compounds were responsible for a strongly variety-dependent ozone uptake of plants under dark conditions, when stomatal pores are almost closed. Surface reactions of ozone were accompanied by a prompt release of oxygenated volatile organic compounds, which could be linked to the corresponding precursor compounds: ozonolysis cis-abienol (C20H34O) – a diterpenoid with two exocyclic double bonds – caused emissions of formaldehyde (HCHO) and methyl vinyl ketone (C4H6O). The ring-structured cembratrien-diols (C20H34O2) with three endocyclic double bonds need at least two ozonolysis steps to form volatile carbonyls such as 4-oxopentanal (C5H8O2), which we could observe in the gas phase, too. Fluid dynamic calculations were used to model ozone distribution in the diffusion-limited leaf boundary layer under daylight conditions. In the case of an ozone-reactive leaf surface, ozone gradients in the vicinity of stomatal pores are changed in such a way that the ozone flux through the open stomata is strongly reduced. Our results show that unsaturated semi-volatile compounds at the plant surface should be considered as a source of oxygenated volatile organic compounds, impacting gas phase chemistry, as well as efficient ozone sink improving the ozone tolerance of plants

Does asymptomatic mean without symptoms for those living with HIV infection?

Throughout the history of the HIV epidemic, HIV-positive patients with relatively high CD4 counts and no clinical features of opportunistic infections have been classified as asymptomatic by definition and treatment guidelines. This classification, however, does not take into consideration the array of symptoms that an HIV-positive person can experience long before progressing to AIDS. This short report describes two international multi-site studies conducted in 2003-2005 and 2005-2007. The results from the studies show that HIV-positive people may experience symptoms throughout the trajectory of their disease, regardless of CD4 count or classification. Providers should discuss symptoms and symptom management with their clients at all stages of the disease

Infecciones del tracto urinario bajo en adultos y embarazadas: consenso para el manejo empírico

Introducción: La infección no complicada del tracto urinario bajo y la bacteriuria asintomática son causas frecuentes de consulta médica ambulatoria y en el servicio de urgencias en Colombia y el mundo. La falta de pautas y consenso para el manejo, así como la emergencia de resistencia a las múltiples opciones terapéuticas disponibles en los uropatógenos provenientes de la comunidad, hacen necesario elaborar unas recomendaciones que orienten al clínico sobre el abordaje óptimo de estas entidades. Objetivo: Definir un consenso sobre el manejo empírico de la bacteriuria asintomática y la infección del tracto urinario (ITU) bajo en adultos y mujeres embarazadas en Colombia. Metodología: Se lleva a cabo una metodología de consenso con expertos en urología, infectología, medicina interna, ginecología y microbiología basada en la revisión de las referencias bibliográficas disponibles en los términos de búsqueda relacionados, haciendo énfasis en estudios locales. Resultados: Se elaboró un algoritmo de manejo para el tratamiento empírico de la ITU baja no complicada en adultos con antisépticos urinarios como nitrofurantoína y fosfomicina trometamol como primera línea, con recomendaciones terapéuticas específicas para el tratamiento de la bacteriuria asintomática en mujeres embarazadas. Adicionalmente, se formuló un algoritmo de decisión para el procesamiento de cultivos de orina. La recurrencia o recaída frecuente justifica remisión a urología e infectología. Conclusiones: Se generan recomendaciones prácticas de fácil implementación en el diagnóstico y manejo de la ITU bajo en adultos y embarazadas, y de los casos donde es necesario tratar la bacteriuria asintomática, con opciones terapéuticas efectivas y de espectro reducido