In vivo airway surface liquid Cl- analysis with solid-state electrodes.

The pathogenesis of cystic fibrosis (CF) airways disease remains controversial. Hypotheses that link mutations in CFTR and defects in ion transport to CF lung disease predict that alterations in airway surface liquid (ASL) isotonic volume, or ion composition, are critically important. ASL [Cl-] is pivotal in discriminating between these hypotheses, but there is no consensus on this value given the difficulty in measuring [Cl-] in the "thin" ASL (approximately 30 microm) in vivo. Consequently, a miniaturized solid-state electrode with a shallow depth of immersion was constructed to measure ASL [Cl-] in vivo. In initial experiments, the electrode measured [Cl-] in physiologic salt solutions, small volume (7.6 microl) test solutions, and in in vitro cell culture models, with > or =93% accuracy. Based on discrepancies in reported values and/or absence of data, ASL Cl- measurements were made in the following airway regions and species. First, ASL [Cl-] was measured in normal human nasal cavity and averaged 117.3 +/- 11.2 mM (n = 6). Second, ASL [Cl-] measured in large airway (tracheobronchial) regions were as follows: rabbit trachea and bronchus = 114.3 +/- 1.8 mM; (n = 6) and 126.9 +/- 1.7 mM; (n = 3), respectively; mouse trachea = 112.8 +/- 4.2 mM (n = 13); and monkey bronchus = 112.3 +/- 10.9 mM (n = 3). Third, Cl- measurements were made in small (1-2 mm) diameter airways of the rabbit (108.3 +/- 7.1 mM, n = 5) and monkey (128.5 +/- 6.8 mM, n = 3). The measured [Cl-], in excess of 100 mM throughout all airway regions tested in multiple species, is consistent with the isotonic volume hypothesis to describe ASL physiology.     

纳米SiO2对poss复合树脂弯曲和抗压强度的影响

目的：观察纳米SiO2填料对纳米复合树脂poss的弯曲强度和抗压强度的影响,探究纳米SiO2的最佳添加比。方法：将经过硅烷偶联化的纳米SiO2颗粒加入poss复合树脂中,合成SiO2质量分数分别为0．5％,1％,1．5％和2％的Si02／poss复合树脂,分别为BCDE四组,纯poss组为A组（对照组）。每组试件固定于万能材料测试机上,以1．0mm／min的速度垂直加压直至试样破坏,采用SPSSl6．0软件对结果做单因素方差分析。结果：弯曲强度测试结果：C组最高,与其他四组均有统计学差异（P〈0．05）;A、B、D三组无显著性差异,与E组差异明显（P〈0．05）。抗压强度测试结果：D组最高,与其他四组均有统计学差异（P〈0．05）;B组和E组与A组差异显著（P〈0．05）,与C组无显著差异。结论：纳米SiO2在一定范围内能够提高poss复合树脂的弯曲强度和抗压强度。     

Predicting the unexpected: using a qualitative model of a New Zealand dryland ecosystem to anticipate pest management outcomes

Pest management is expensive and there is often uncertainty about the benefits for the resources being protected. There can also be unintended consequences for other parts of the ecosystem, especially in complex food webs. In making decisions managers generally have to rely on qualitative information collected in a piecemeal fashion. A method to assist decision making is a qualitative modelling approach using fuzzy cognitive maps, a directed graphical model related to neural networks that can take account of interactions between pests and conservation assets in complex food webs. Using all available information on relationships between native and exotic resources and consumers, we generated hypotheses about potential consequences of single‐species and multi‐species pest control on the long‐term equilibrium abundances of other biotic components of an ecosystem. We applied the model to a dryland ecosystem in New Zealand because we had good information on its trophic structure, but the information on the strength of species interactions was imprecise. Our model suggested that pest control is unlikely to significantly boost native invertebrates and lizards in this ecosystem, suggesting that other forms of management may be required for these groups. Most of the pest control regimes tested resulted in greater abundances of at least one other pest species, which could potentially lead to other management problems. Some of the predictions were unexpected, such as more birds resulting from possum and mouse control. We also modelled the effects of an increase in invasive rabbits, which led to unexpected declines of stoats, weasels, mice and possums. These unexpected outcomes resulted from complex indirect pathways in the food web. Fuzzy cognitive maps allow rapid construction of prototype models of complex food webs using a wide range of data and expert opinion. Their utility lies in providing direction for future monitoring efforts and generating hypotheses that can be tested with field experiments.     

Accuracy of specimen-specific nonlinear finite element analysis for evaluation of radial diaphysis strength in cadaver material

The feasibility of a user-specific finite element model for predicting the in situ strength of the radius after implantation of bone plates for open fracture reduction was established. The effect of metal artifact in CT imaging was characterized. The results were verified against biomechanical test data. Fourteen cadaveric radii were divided into two groups: (1) intact radii for evaluating the accuracy of radial diaphysis strength predictions with finite element analysis and (2) radii with a locking plate affixed for evaluating metal artifact. All bones were imaged with CT. In the plated group, radii were first imaged with the plates affixed (for simulating digital plate removal). They were then subsequently imaged with the locking plates and screws removed (actual plate removal). Fracture strength of the radius diaphysis under axial compression was predicted with a three-dimensional, specimen-specific, nonlinear finite element analysis for both the intact and plated bones (bones with and without the plate captured in the scan). Specimens were then loaded to failure using a universal testing machine to verify the actual fracture load. In the intact group, the physical and predicted fracture loads were strongly correlated. For radii with plates affixed, the physical and predicted (simulated plate removal and actual plate removal) fracture loads were strongly correlated. This study demonstrates that our specimen-specific finite element analysis can accurately predict the strength of the radial diaphysis. The metal artifact from CT imaging was shown to produce an overestimate of strength.     

Performance of oak,beech and spruce beams after more than 100 years in service

The aim of this study was to investigate differences in the mechanical and fungicidal properties of three different wood species (English oak (Quercus sp.), common beech (Fagus sylvatica) and Norway spruce (Picea abies)) that had been in indoor use for several decades, compared to control specimens of freshly cut timber. The collected material was cut into smaller samples prior to further analysis. Extractive content, mechanical, fungicidal and sorption properties were determined according to standard procedures. The obtained results showed that the mechanical properties of oak wood do not deteriorate over the investigated time frame. On the other hand, the resistance of oak wood against fungi decreases over time. The reason for this is yet to be confirmed; it may be due to degradation of secondary metabolites. Similar results have been reported for spruce wood. There were no statistically significant differences in the mechanical properties of old and new spruce wood. In contrast to oak wood, there were also no significant differences in fungicidal properties, bearing in mind that spruce wood has lower durability than oak wood. Aging of beech wood resulted in a considerable decrease in the tested mechanical properties but showed no significant differences in fungicidal properties. Old beech wood specimens were moderately deteriorated by insects and fungi, which was the reason for the loss of bending and compressive strength. Our results confirm that most of the relevant properties do not deteriorate with time and that wood can be reused for a variety of other applications even after decades in service.     

Genetic differences in fruit-set patterns are determined by differences in fruit sink strength and a source : sink threshold for fruit set

Background and Aims

Fruit set in indeterminate plant species largely depends on the balance between source and sink strength. Plants of these species show fluctuations in fruit set during the growing season. It was tested whether differences in fruit sink strength among the cultivars explained the differences in fruit-set patterns.

Methods

Capsicum was chosen as a model plant. Six cultivars with differences in fruit set, fruit size and plant growth were evaluated in a greenhouse experiment. Fruit-set patterns, generative and vegetative sink strength, source strength and the source : sink ratio at fruit set were determined. Sink strength was quantified as potential growth rate. Fruit set was related to total fruit sink strength and the source : sink ratio. The effect of differences observed in above-mentioned parameters on fruit-set patterns was examined using a simple simulation model.

Key Results

Sink strengths of individual fruits differed greatly among cultivars. Week-to-week fruit set in large-fruited cultivars fluctuated due to large fluctuations in total fruit sink strength, but in small-fruited cultivars, total fruit sink strength and fruit set were relatively constant. Large variations in week-to-week fruit set were correlated with a low fruit-set percentage. The source : sink threshold for fruit set was higher in large-fruited cultivars. Simulations showed that within the range of parameter values found in the experiment, fruit sink strength and source : sink threshold for fruit set had the largest impact on fruit set: an increase in these parameters decreased the average percentage fruit set and increased variation in weekly fruit set. Both were needed to explain the fruit-set patterns observed. The differences observed in the other parameters (e.g. source strength) had a lower effect on fruit set.

Conclusions

Both individual fruit sink strength and the source : sink threshold for fruit set were needed to explain the differences observed between fruit-set patterns of the six cultivars.     

Immobilization and bone structure in humans

Long-term immobilization is known to result in substantial bone loss. The present review examined the existing evidence for deterioration of bone structure during long-term disuse in humans. Paralysis due to spinal cord injury, long-term exposure to microgravity in space or tightly restricted mobility during bed rest provide reasonable models to assess the influence of immobilization on bone structure. Expectedly, the duration of immobilisation was the major determinant of bone loss, but irrespective of whether the skeletal unloading was due to irrecoverable paralysis, long-term spaceflight or bed rest, the mean pattern of structural deterioration of bone, mainly manifest as substantial cortical thinning and trabecular bone loss, was quite similar. However, skeletal responses to disuse can be highly variable between individuals. Apparently the relative decline in individual’s bone loading in relation to loading prior to immobilization accounts for inter-individual variation.