17 O-excess and d-excess of atmospheric water vapor measured by cavity ring-down spectrometry: Evidence of a matrix effect and implication for the calibration procedure.

RATIONALE: Producing robust high-frequency time series of raw atmospheric water vapor isotope data using laser spectrometry requires accurate calibration. In particular, the chemical composition of the analyzed sample gas can cause isotope bias. This study assesses the matrix effect on calibrated δ17 O, δ18 O, δ2 H, 17 O-excess, and d-excess values of atmospheric water vapor. METHODS: A Picarro L2140-i cavity ring-down spectrometer with an autosampler and a vaporizer is used to analyze δ17 O, δ18 O, δ2 H, 17 O-excess, and d-excess of two water standards. Isotope data obtained using synthetic air and dry ambient air as carrier gas at water mixing ratios ranging from 2000 to 30 000 ppmv are compared. Based on the results, atmospheric water vapor measurements are calibrated. The expected precision is estimated by Monte Carlo simulation. RESULTS: The dry air source strongly impacts raw isotope values of the two water standards but has no effect on the mixing ratio dependency functions. When synthetic air is used, δ17 O, δ18 O, and 17 O-excess of calibrated atmospheric water vapor are overestimated by 0.6‰, 0.7‰, and 217 per meg, respectively, whereas δ2 H and d-excess are underestimated by 1.5‰ and 7.3‰. Optimum precisions for the calibrated δ17 O, δ18 O, δ2 H, 17 O-excess, and d-excess values and 12 min integration time are 0.02‰, 0.03‰, 0.4‰, 14 per meg, and 0.4‰, respectively. CONCLUSIONS: Regarding the obtained results, recommendations for the calibration of atmospheric water vapor isotope measurements are presented. The necessity to use dry ambient air as dry air source when running the standards for calibration is pointed out as a prerequisite for accurate atmospheric water vapor 17 O-excess and d-excess measurements.

Dynamic Nuclear Polarization NMR as a new tool to investigate the nature of organic compounds occluded in plant silica particles.

The determination of the chemical nature of the organic matter associated with phytoliths remains a challenge. This difficulty mainly stems from amounts of organic carbon (C) that are often well below the detection limit of traditional spectroscopic tools. Conventional solid-state 13C Nuclear Magnetic Resonance (NMR) is widely used to examine the nature and structure of organic molecules, but its inherent low sensitivity prohibits the observation of diluted samples. The recent advent of commercial microwave source in the terahertz range triggered a renewed interest in the Dynamic Nuclear Polarization (DNP) technique to improve the signal to noise ratio of solid-state NMR experiments. With this technique, the 13C spectrum of a phytolith sample containing 0.1% w/w C was obtained overnight with sufficient quality to permit a semi-quantitative analysis of the organic matter, showing the presence of peptides and carbohydrates as predominant compounds. Considering the natural abundance of the 13C isotope, this experiment demonstrates that DNP NMR is sufficiently sensitive to observe spin systems present in amounts as low as a few tens of ppm.

Environmental factors related to the production of a complex set of spicules in a tropical freshwater sponge.

Adverse natural conditions will, generally, induce gemmulation in freshwater sponges. Because of this environmental dependence, gemmoscleres are given exceptional value in taxonomic, ecological and paleoenvironmental studies. Other spicules categories such as microscleres and beta megascleres have received little attention with regard to their occurrence and function during the sponge biological cycle. Metania spinata, a South American species common to bog waters in the Cerrado biome, produces alpha and beta megascleres, microscleres and gemmoscleres. To detect the environmental factors triggering the production of all these kinds of spicules, the species annual seasonal cycle was studied. Artificial substrates were devised, supplied with gemmules and placed in Lagoa Verde pond which contained a natural population of M. spinata. Field monitoring was conducted for eight months in order to observe the growth of sponges and spicules formation. Samples of water were taken monthly for physical and chemical parameters determination. The appearance of the alpha megascleres was sequentially followed by that of microscleres, gemmoscleres and beta megascleres. The first ones built the new sponge skeleton, the last three were involved in keeping inner moisture in the sponge body or its gemmules. The water level, temperature and the silicon (Si) concentration in the pond were the most important factors related to this sequential production of spicules, confirming environmental reconstructions based on the presence or absence of alpha megascleres and gemmoscleres in past sediments.

Prevalência e práticas preventivas em infertilidade entre mulheres atendidas em um serviço público de saúde / Prevalence and preventive practices in infertility among women attending a public health service

Objetivo: O estudo foi feito a fim de avaliar o conhecimento e a prática de medidas preventivas em infertilidade. Método: Durante um mês foi aplicado um questionário às pacientes que frequentam o Ambulatório de Ginecologia da Universidade Federal de Pelotas, de modo consentido e sem se identificar, com perguntas relacionadas à prevenção de infertilidade. Resultados: Os resultados mostram que entre 134 mulheres entrevistadas, 68% nunca se preocuparam com não conseguir ter filhos, 62% responderam saber da existência de medidas que podem prevenir a infertilidade, 49% são sedentárias, 72% fazem uso de preservativos, 36% fumam, 84% evitam ingesta de bebida alcoólica em excesso, 94% não fazem uso de drogas ilícitas, 61% controlam o peso, 77% pensam em ter filhos antes dos 35 anos e 87% consultam regularmente um ginecologista. Conclusão: O índice de apenas 32% das mulheres entrevistadas que se preocupam com não conseguir ter filhos revela a falta de conhecimentos sobre o problema. Embora 62% delas referiram ter conhecimento de medidas que podem prevenir a infertilidade, acredita-se que esse percentual seja menor na população em geral.

Objective: This study was conducted to assess the knowledge and practice of preventive measures in infertility. Methods: For one month a questionnaire was administered to patients who attend the Gynecology, Federal University of Pelotas, so consented and without identifying themselves, with questions related to prevention of infertility. Results: The results show that among 134 women interviewed, 68% never bothered to not be able to have children, 62% said they knew about the measures that can prevent infertility, 49% is sedentary, 72% makes use of condoms, 36% smoke, 84% avoid ingestion of alcohol in excess, 94% did not use illegal drugs, 61% controls weight, 77% think having children before 35 years and 87% of the group regularly consults a gynecologist. Conclusion: Since only 32% of women are concerned with can’t have children, reveals a lack of knowledge about the problem. Although 62% of them reported that he is aware of measures which can prevent infertility, it is believed that this percentage is smaller in the general population.

IR laser extraction technique applied to oxygen isotope analysis of small biogenic silica samples.

An IR-laser fluorination technique is reported here for analyzing the oxygen isotope composition (delta18O) of microscopic biogenic silica grains (phytoliths and diatoms). Performed after a controlled isotopic exchanged (CIE) procedure, the laser fluorination technique that allows one to visually check the success of the fluorination reaction is faster than the conventional fluorination technique and allows analyzing delta18O of small to minute samples (1.6-0.3 mg) as required for high-resolution paleoenvironmental reconstructions. The long-term reproducibility achieved with the IR laser-heating fluorination/O2 delta18O analysis is lower than or equal to +/-0.26 per thousand (1 SD; n = 99) for phytoliths and +/-0.17 per thousand (1 SD; n = 47) for diatoms. When several CIE are taken into account in the SD calculation, the resulting reproducibility is lower than or equal to +/-0.51 per thousand for phytoliths (1 SD; n = 99; CIE > 5) and +/-0.54 per thousand (1 SD; n = 47; CIE = 13) for diatoms. A minimum reproducibility of +/-0.5 per thousand leads to an estimated uncertainty on delta18Osilica close to +/-0.5 per thousand. Resulting uncertainties on reconstructed temperature and delta18Oforming water are, respectively, +/-2 degrees C and +/-0.5 per thousand and fit in the precisions required for intertropical paleoenvironmental reconstructions. Several methodological points such as optimal extraction protocols and the necessity or not of performing two CIE prior to oxygen extraction are assessed.