Oxygen fractionation in dense molecular clouds.

We have developed the first gas-grain chemical model for oxygen fractionation (also including sulphur fractionation) in dense molecular clouds, demonstrating that gas-phase chemistry generates variable oxygen fractionation levels, with a particularly strong effect for NO, SO, O2, and SO2. This large effect is due to the efficiency of the neutral 18O + NO, 18O + SO, and 18O + O2 exchange reactions. The modeling results were compared to new and existing observed isotopic ratios in a selection of cold cores. The good agreement between model and observations requires that the gas-phase abundance of neutral oxygen atoms is large in the observed regions. The S16O/S18O ratio is predicted to vary substantially over time showing that it can be used as a sensitive chemical proxy for matter evolution in dense molecular clouds.

Clustering the Orion B giant molecular cloud based on its molecular emission.

CONTEXT: Previous attempts at segmenting molecular line maps of molecular clouds have focused on using position-position-velocity data cubes of a single molecular line to separate the spatial components of the cloud. In contrast, wide field spectral imaging over a large spectral bandwidth in the (sub)mm domain now allows one to combine multiple molecular tracers to understand the different physical and chemical phases that constitute giant molecular clouds (GMCs). AIMS: We aim at using multiple tracers (sensitive to different physical processes and conditions) to segment a molecular cloud into physically/chemically similar regions (rather than spatially connected components), thus disentangling the different physical/chemical phases present in the cloud. METHODS: We use a machine learning clustering method, namely the Meanshift algorithm, to cluster pixels with similar molecular emission, ignoring spatial information. Clusters are defined around each maximum of the multidimensional Probability Density Function (PDF) of the line integrated intensities. Simple radiative transfer models were used to interpret the astrophysical information uncovered by the clustering analysis. RESULTS: A clustering analysis based only on the J = 1 - 0 lines of three isotopologues of CO proves suffcient to reveal distinct density/column density regimes (nH ~ 100 cm-3, ~ 500 cm-3, and > 1000 cm-3), closely related to the usual definitions of diffuse, translucent and high-column-density regions. Adding two UV-sensitive tracers, the J = 1 - 0 line of HCO+ and the N = 1 - 0 line of CN, allows us to distinguish two clearly distinct chemical regimes, characteristic of UV-illuminated and UV-shielded gas. The UV-illuminated regime shows overbright HCO+ and CN emission, which we relate to a photochemical enrichment effect. We also find a tail of high CN/HCO+ intensity ratio in UV-illuminated regions. Finer distinctions in density classes (nH ~ 7 × 103 cm-3 ~ 4 × 104 cm-3) for the densest regions are also identified, likely related to the higher critical density of the CN and HCO+ (1 - 0) lines. These distinctions are only possible because the high-density regions are spatially resolved. CONCLUSIONS: Molecules are versatile tracers of GMCs because their line intensities bear the signature of the physics and chemistry at play in the gas. The association of simultaneous multi-line, wide-field mapping and powerful machine learning methods such as the Meanshift clustering algorithm reveals how to decode the complex information available in these molecular tracers.

First Detection of Interstellar S2H.

We present the first detection of gas phase S2H in the Horsehead, a moderately UV-irradiated nebula. This confirms the presence of doubly sulfuretted species in the interstellar medium and opens a new challenge for sulfur chemistry. The observed S2H abundance is ~5×10-11, only a factor 4-6 lower than that of the widespread H2S molecule. H2S and S2H are efficiently formed on the UV-irradiated icy grain mantles. We performed ice irradiation experiments to determine the H2S and S2H photodesorption yields. The obtained values are ~1.2×10-3 and <1×10-5 molecules per incident photon for H2S and S2H, respectively. Our upper limit to the S2H photodesorption yield suggests that photo-desorption is not a competitive mechanism to release the S2H molecules to the gas phase. Other desorption mechanisms such as chemical desorption, cosmic-ray desorption and grain shattering can increase the gaseous S2H abundance to some extent. Alternatively, S2H can be formed via gas phase reactions involving gaseous H2S and the abundant ions S+ and SH+. The detection of S2H in this nebula could be therefore the result of the coexistence of an active grain surface chemistry and gaseous photo-chemistry.

The comet-like composition of a protoplanetary disk as revealed by complex cyanides.

Observations of comets and asteroids show that the solar nebula that spawned our planetary system was rich in water and organic molecules. Bombardment brought these organics to the young Earth's surface. Unlike asteroids, comets preserve a nearly pristine record of the solar nebula composition. The presence of cyanides in comets, including 0.01 per cent of methyl cyanide (CH3CN) with respect to water, is of special interest because of the importance of C-N bonds for abiotic amino acid synthesis. Comet-like compositions of simple and complex volatiles are found in protostars, and can readily be explained by a combination of gas-phase chemistry (to form, for example, HCN) and an active ice-phase chemistry on grain surfaces that advances complexity. Simple volatiles, including water and HCN, have been detected previously in solar nebula analogues, indicating that they survive disk formation or are re-formed in situ. It has hitherto been unclear whether the same holds for more complex organic molecules outside the solar nebula, given that recent observations show a marked change in the chemistry at the boundary between nascent envelopes and young disks due to accretion shocks. Here we report the detection of the complex cyanides CH3CN and HC3N (and HCN) in the protoplanetary disk around the young star MWC 480. We find that the abundance ratios of these nitrogen-bearing organics in the gas phase are similar to those in comets, which suggests an even higher relative abundance of complex cyanides in the disk ice. This implies that complex organics accompany simpler volatiles in protoplanetary disks, and that the rich organic chemistry of our solar nebula was not unique.

Chemical complexity in the horsehead photodissociation region.

The interstellar medium is known to be chemically complex. Organic molecules with up to 11 atoms have been detected in the interstellar medium, and are believed to be formed on the ices around dust grains. The ices can be released into the gas-phase either through thermal desorption, when a newly formed star heats the medium around it and completely evaporates the ices; or through non-thermal desorption mechanisms, such as photodesorption, when a single far-UV photon releases only a few molecules from the ices. The first mechanism dominates in hot cores, hot corinos and strongly UV-illuminated PDRs, while the second dominates in colder regions, such as low UV-field PDRs. This is the case of the Horsehead were dust temperatures are approximately eual to 20-30 K, and therefore offers a clean environment to investigate the role of photodesorption. We have carried out an unbiased spectral line survey at 3, 2 and 1mm with the IRAM-30m telescope in the Horsehead nebula, with an unprecedented combination of bandwidth, high spectral resolution and sensitivity. Two positions were observed: the warm PDR and a cold condensation shielded from the UV field (dense core), located just behind the PDR edge. We summarize our recently published results from this survey and present the first detection of the complex organic molecules HCOOH, CH2CO, CH3CHO and CH3CCH in a PDR. These species together with CH3CN present enhanced abundances in the PDR compared to the dense core. This suggests that photodesorption is an efficient mechanism to release complex molecules into the gas-phase in far-UV illuminated regions.

Competencia cultural para enfermeras hospitalares que cuidan pacientes con enfermedad crónica / Cultural competence for hospital nurses caring for patients with chronic illness

Antecedentes: Colombia es culturalmente diversa y vive procesos de desplazamiento forzado por la violencia siendo uno de los países con mayor desplazamiento interno del mundo. Colombia tiene alta morbilidad y mortalidad por las enfermedades crónicas. Las enfermeras en los hospitales deben cuidar de esas poblaciones de diversos orígenes pero se desconoce si tienen competencia cultural para hacerlo. Objetivo: Describir la competencia cultural expresada por Enfermeras hospitalares, cuando cuidan a pacientes con Enfermedad Crónica. Metodología: Estudio etnográfico interpretativo. Hicieron parte del estudio diez PE con más de un año de trabajo en el Hospital San Antonio con personas adultas con enfermedad crónica en el hospital. Los datos fueron recogidos de la observación participante, grupo focal, seis entrevistas etnográficas y diez narrativas después de 14 meses de trabajo en campo. El análisis de los datos siguieron las fases propuestas por Leininger en un proceso inductivo ­ deductivo. La confirmabilidad, transferibilidad, auditabilidad y credibilidad hicieron parte del rigor metodológico. Todos los aspectos éticos fueron considerados. Resultados: Los hallazgos muestran un tema cultural: Intento por responder al asunto cultural de los pacientes desde mi ética profesional como algo implícito en la práctica de las EH. Así intentan respetar, aprender, ser sensibles y responder a los pacientes de diversos orígenes buscando dignificarlos, este no es un proceso sistemático. Finalmente se concluye que hay un aprendizaje práctico de la experiencia haciendo que no se tenga el conocimiento, ni la habilidad pero si la conciencia de sí, la parte ética las mueve y es ahí donde responden. (AU)

Background: Colombia is culturally diverse and live processes of forced displacement by violence remains one of the countries with the largest internal displacement in the world. Colombia has high morbidity and mortality from chronic diseases. Nurses in hospitals must care for these populations but whether they have the cultural competence. Objective: To describe cultural competence expressed by nurses hospitals when caring for patients with Chronic Disease. Methodology: Interpretive Ethnographic study. They were part of the study ten nurses more than a year of work in the San Antonio Hospital with adults with chronic disease nurses in the hospital. Data were collected from participant observation, focus groups, and ethnographic interviews with six nurses and ten plots after 14 months of field work. The data analysis followed the steps proposed in an inductive process Leininger - deductive. Confirmability, transferability, auditability and credibility are considered as part of the methodological rigor. All ethical issues were considered. Results: The findings show a cultural issue: I try to respond to the cultural issue of patients from my professional ethics as something implicit in the practice of nurses. So nurses try to respect, learn, be sensitive and respond to patients from diverse backgrounds seeking dignify this is not a systematic process. Finally it is concluded that there is a practical learning experience making knowledge is known, but not the ability of self-consciousness, the ethical part the moves and that is where they respond. (AU)

Presencia de Listeria monocytogenes en alimentos listos para el consumo, procedentes de plazas de mercado y delicatessen de supermercados de cadena, Bogotá, D. C, 2002-2008 / Presence of Listeria monocytogenes in ready-to-eat foods available in open markets, delicatessens and supermarkets, Bogotá, 2002-2008

Introducción. El aumento de las enfermedades transmitidas por alimentos se ha constituido en un problema de salud pública. La listeriosis, cuyo agente etiológico es Listeria monocytogenes, es considerada de gran relevancia entre las ellas y los alimentos listos para el consumo de ventas al por menor son de gran riesgo. Objetivo. Identificar la presencia de L. monocytogenes en alimentos listos para el consumo, procedentes de plazas de mercado y delicatessen de Bogotá.Materiales y métodos. Se llevó a cabo un estudio descriptivo transversal con componente analítico, en el cual se analizaron 600 alimentos, 300 de delicatessen y 300 de plazas de mercado. Se utilizaron metodologías de referencia de presencia o ausencia de L. monocytogenes en 25 g o mililitros de alimento. Resultados. De las 600 muestras analizadas, 68 fueron positivas para L. monocytogenes (11,3 %), 26 (38,25 %) procedieron de delicatessen, 42 (61,76 %) de plazas de mercado. El serotipo aislado con mayor frecuencia fue 4b en 53 (78 %) aislamientos. Los quesos frescos y los quesos madurados mostraron mayor contaminación de L. monocytogenes que el resto de alimentos del estudio (p=0,0009/0,0003).Conclusión. Los resultados indican que estos alimentos son vehículos de transmisión del microorganismo, convirtiéndolos en potenciales alimentos de alto riesgo; deben ser vigilados y controlados por la autoridad competente. Se requieren programas para implementar la normativa sobre vigilancia, reducción y control de este microorganismo con miras hacia la prevención de las enfermedades transmitidas por alimentos.

Introduction. The increase in diseases transmitted by foods has become a public health problem. Listeria monocytogenes, the etiological agent of listeriosis or typical food poisoning, is considered to be among the most important food borne illnesses. High risk foods for L.monocytogenes have been recognized as foods already prepared for consumption and made available in retail outlets. Objective. The presence of L. monocytogenes was identified in prepared foods found in open markets and delicatessens in the city of Bogotá.Material and methods. A transverse descriptive study over a 7-year period, with an analytic component, in which 600 foods were analyzed--300 from delicatessens and 300 from open market places. Reference methods were used to determine the presence or absence of L. monocytogenes in 25 grams or milliliters a food sample. Results. Of the 600 samples, 68 were positive for L. monocytogenes (11.3%). Twenty-six (38.2%) were taken from delicatessens and 42 (61.8%) from open market places. The serotype most frequently isolated was 4b, with 53 (78.0%) isolations. Fresh cheeses and matured cheeses showed greater contamination with L. monocytogenes than the other foods (p<0.001 in both cases).Conclusions. The results indicate that prepared foods are vehicles for the transmission of the Listeria bacterium. These potentially high risk foods are candidates for control and monitoring by public health authorities. Programs must be instituted to implement surveillance norms that lead to the reduction and control of this microorganism and geared toward the prevention of food borne diseases.

[Presence of Listeria monocytogenes in ready-to-eat foods available in open markets, delicatessens and supermarkets, Bogotá, 2002-2008]. / Presencia de Listeria monocytogenes en alimentos listos para el consumo, procedentes de plazas de mercado y delicatessen de supermercados de cadena, Bogotá, D.C, 2002-2008.

INTRODUCTION: The increase in diseases transmitted by foods has become a public health problem. Listeria monocytogenes, the etiological agent of listeriosis or typical food poisoning,is considered to be among the most important food borne illnesses. High risk foods for L.monocytogenes have been recognized as foods already prepared for consumption and made available in retail outlets. OBJECTIVE: The presence of L. monocytogenes was identified in prepared foods found in open markets and delicatessens in the city of Bogotá. MATERIAL AND METHODS: A transverse descriptive study over a 7-year period, with an analytic component, in which 600 foods were analyzed--300 from delicatessens and 300 from open market places. Reference methods were used to determine the presence or absence of L. monocytogenes in 25 grams or milliliters a food sample. RESULTS: Of the 600 samples, 68 were positive for L. monocytogenes (11.3%). Twenty-six (38.2%) were taken from delicatessens and 42 (61.8%) from open market places. The serotype most frequently isolated was 4b, with 53 (78.0%) isolations. Fresh cheeses and matured cheeses showed greater contamination with L. monocytogenes than the other foods (p<0.001 in both cases). CONCLUSIONS: The results indicate that prepared foods are vehicles for the transmission of the Listeria bacterium. These potentially high risk foods are candidates for control and monitoring by public health authorities. Programs must be instituted to implement surveillance norms that lead to the reduction and control of this microorganism and geared toward the prevention of food borne diseases.