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491.
In talipes equino-varus the diminished bulk of the calf muscle suggests a neuromuscular defect. Accordingly, biopsies were taken from the postero-medial and peroneal muscle groups, and occasionally from abductor hallucis, in sixty patients mostly under the age of five years; 111 were studied histochemically and histologically, and a further fifty-three by electron-microscopy. Histochemical anomalies were revealed in ninety-two specimens; the muscle fibres in the other nineteen varied in size but were abnormal at the ultramicroscopic level, as were all specimens examined with the electron microscope. Evidence of neurogenic disease was seen in most instances and was more obvious in the older patients. The pattern of abnormality was similar in both muscle groups. It is thought that shortening of the postero-medial muscles may result from a small increase of fibrosis due to minor innervation changes occurring in intra-uterine life. There is evidence that immobilisation, stretching or relaxation of muscles does not account for the anomalies observed. This study of the extrinsic muscles in talipes equino-varus indicates a dominant neurogenic factor in its causation. 相似文献
492.
Karla Calfumán Maria Jesús Aguirre Paulina Cañete-Rosales Soledad Bollo Rosa Llusar Mauricio Isaacs 《Electrochimica acta》2011,56(24):8484
This paper describes the electrochemical reduction of nitrite ion in neutral aqueous solution mediated by tetraruthenated metalloporphyrins (Co(II), Ni(II) and Zn(II)) electrostatically assembled onto a Nafion film previously adsorbed on glassy carbon or ITO electrodes. Scanning electron microscope (SEM-EDX) and transmission electron microscopy (TEM) results have shown that on ITO electrodes the macrocycles forms multiple layers with a disordered stacking orientation over the Nafion film occupying hydrophobic and hydrophilic sites in the polyelectrolyte. Atomic force microscopy (AFM) results demonstrated that the Nafion film is 35 nm thick and tetraruthenated metalloporphyrins layers 190 nm thick presenting a thin but compacted morphology. Scanning electrochemical microscopy (SECM) images shows that the Co(II) tetraruthenated porphyrins/Nf/GC modified electrode is more electrochemically active than their Ni and Zn analogues.These modified electrodes are able to reduce nitrite at −660 mV showing enhanced reduction current and a decrease in the required overpotential compared to bare glassy carbon electrode. Controlled potential electrolysis experiments verify the production of ammonia, hydrazine and hydroxylamine at potentials where reduction of solvent is plausible demonstrating some selectivity toward the nitrite ion. Rotating disc electrode voltammetry shows that the factor that governs the kinetics of nitrite reduction is the charge propagation in the film. 相似文献
493.
In Rwanda, farmers’ traditional farming systems based on intercropping and varietal mixtures are designed to meet a variety of livelihood objectives and withstand risks associated with fluctuation in market and agro-climatic conditions. However, these mixed systems have been disappearing since 2008 when government mandated intensification strategies. In this paper we use a mixed methods approach to evaluate intercropping and sole cropping systems against farmers’ criteria for success: yield, market value, contribution to nutritional quality, and land-use efficiency. We used qualitative interviews to understand the criteria by which farmers evaluate cropping systems, and data from crop trials to assess common bean ((Phaseolus vulgaris L.) and maize (Zea mays L.)) sole crops and intercrops against those criteria. We found that an improved intercropping system tends to outperform the government-mandated system of alternating sole-cropped bean and maize season-by-season, on all four of the criteria tested. Although Rwanda’s agricultural intensification strategy aims to improve rural livelihoods through agricultural modernization, it fails to acknowledge the multiple and currently non-replaceable benefits that diverse cropping systems provide, particularly food security and risk management. Agricultural policies need to be based on a better understanding of smallholders’ objectives and constraints. Efforts to improve farming systems require innovative and inclusive approaches that enable adaptation to the socio-ecological context. 相似文献
494.
New perspectives on nanomaterial aquatic ecotoxicity: production impacts exceed direct exposure impacts for carbon nanotoubes 总被引:1,自引:0,他引:1
Eckelman MJ Mauter MS Isaacs JA Elimelech M 《Environmental science & technology》2012,46(5):2902-2910
Environmental impacts due to engineered nanomaterials arise both from releases of the nanomaterials themselves as well as from their synthesis. In this work, we employ the USEtox model to quantify and compare aquatic ecotoxicity impacts over the life cycle of carbon nanotubes (CNTs). USEtox is an integrated multimedia fate, transport, and toxicity model covering large classes of organic and inorganic substances. This work evaluates the impacts of non-CNT emissions from three methods of synthesis (arc ablation, CVD, and HiPco), and compares these to the modeled ecotoxicity of CNTs released to the environment. Parameters for evaluating CNT ecotoxicity are bounded by a highly conservative "worst case" scenario and a "realistic" scenario that draws from existing literature on CNT fate, transport, and ecotoxicity. The results indicate that the ecotoxicity impacts of nanomaterial production processes are roughly equivalent to the ecotoxicity of CNT releases under the unrealistic worst case scenario, while exceeding the results of the realistic scenario by 3 orders of magnitude. Ecotoxicity from production processes is dominated by emissions of metals from electricity generation. Uncertainty exists for both production and release stages, and is modeled using a combination of Monte Carlo simulation and scenario analysis. The results of this analysis underscore the contributions of existing work on CNT fate and transport, as well as the importance of life cycle considerations in allocating time and resources toward research on mitigating the impacts of novel materials. 相似文献
495.
ML Steinhauser CM Hogaboam SL Kunkel NW Lukacs RM Strieter TJ Standiford 《Canadian Metallurgical Quarterly》1999,162(1):392-399
To explore the mechanism of immunosuppression associated with sepsis, we developed a murine model of sepsis-induced Pseudomonas aeruginosa pneumonia. CD-1 mice underwent either cecal ligation and 26-gauge needle puncture (CLP) or sham surgery, followed by the intratracheal (i.t.) administration of P. aeruginosa or saline. Survival in mice undergoing CLP followed 24 h later by the i.t. administration of saline or P. aeruginosa was 58% and 10%, respectively, whereas 95% of animals undergoing sham surgery followed by P. aeruginosa administration survived. Increased mortality in the CLP/P. aeruginosa group was attributable to markedly impaired lung bacterial clearance and the early development of P. aeruginosa bacteremia. The i.t. administration of bacteria to CLP-, but not sham-, operated mice resulted in an impressive intrapulmonary accumulation of neutrophils. Furthermore, P. aeruginosa challenge in septic mice resulted in a relative shift toward enhanced lung IL-10 production concomitant with a trend toward decreased IL-12. The i.p., but not i.t., administration of IL-10 Abs given just before P. aeruginosa challenge in septic mice significantly improved both survival and clearance of bacteria from the lungs of septic animals administered P. aeruginosa. Finally, alveolar macrophages isolated from animals undergoing CLP displayed a marked impairment in the ability to ingest and kill P. aeruginosa ex vivo, and this defect was partially reversed by the in vivo neutralization of IL-10. Collectively, these observations indicate that the septic response substantially impairs lung innate immunity to P. aeruginosa, and this effect is mediated primarily by endogenously produced IL-10. 相似文献