生态模型的灵敏度分析

灵敏度分析用于定性或定量地评价模型参数误差对模型结果产生的影响,是模型参数化过程和模型校正过程中的有用工具,具有重要的生态学意义．灵敏度分析包括局部灵敏度分析和全局灵敏度分析．局部灵敏度分析只检验单个参数的变化对模型结果的影响程度;全局灵敏度分析则检验多个参数的变化对模型运行结果总的影响,并分析每一个参数及其参数之间相互作用对模型结果的影响．目前,在对生态模型的灵敏度分析中,越来越倾向于使用全局灵敏度分析的方法．但国内仍多采用局部灵敏度分析方法,很少采用全局灵敏度分析方法．文中详细论述了局部灵敏分析和全局灵敏度分析的主要方法(一次变换法、多元回归法、Morris法、Sobol’法、傅里叶幅度灵敏度检验法和傅里叶幅度灵敏度检验扩展法),希望能为国内生态模型的发展提供一个比较完善的灵敏度分析方法库．结合国内外的灵敏度分析发展现状,指出联合灵敏度研究、灵敏度共性研究及空间直观景观模型的灵敏度分析将为生态模型灵敏度分析研究中的热点和难点．     

Modulation of skin sensitivity by dynamic and isometric exercise in man

The effect of dynamic cycle ergometer exercise and isometric leg exercise on skin sensitivity was studied in man. Exercise was performed at different loads. Cutaneous sensitivity to innocuous and noxious thermal stimuli was tested using a contact thermostimulator and sensitivity to tactile stimuli was tested using electrical stimuli. During isometric exercise a segmental (the exercising limb), but not a multisegmental, phasic decrease of cutaneous thermal sensitivity to innocuous stimuli was found. At the isometric forces used the effect on tactile and heat pain sensitivity was not significant. During dynamic exercise a multisegmental, load-dependent decrease of sensitivity in all tested sensory modalities was found and this attenuation disappeared gradually after the end of exercise. In contrast to isometric exercise, the decrease of sensitivity produced by dynamic exercise was most evident in tactile sensitivity. The size of the stimulus area (7.9 vs 11.8 cm2) did not have a significant effect on the magnitude of the exercise-induced decrease of cutaneous thermal sensitivity to innocuous stimuli. It was concluded that underlying the modulation of skin sensitivity by dynamic and isometric exercise were mechanisms that were different, at least to a small extent. Isometric exercise produced a segmental modulation of skin sensitivity due to central neuronal mechanisms, independent of exercise-induced stress. Exercise-induced stress could have caused the modulation of skin sensitivity by dynamic exercise.     

Adaptive changes in temperature sensitivity in humans under the conditions of cold, heat, and prolonged exercise

In humans adapted for a long time to various conditions—cold, heat, and physical exercise—differently directed changes in temperature sensitivity are observed. During long-term adaptation of humans to cold, a decrease in cold sensitivity is observed. Vice versa, in humans adapted to a hot climate, sensitivity to heat is decreased. Prolonged physical exercise does not change the sensitivity to heat but considerably increases the sensitivity to cold. Some mechanisms and the role of noradrenaline, the postganglionic neurotransmitter of the sympathetic nervous system, in the adaptive processes of a change in temperature sensitivity are considered.     

基于空间距离指数的青藏高原生态敏感性综合评价及时空演变分析

生态敏感性是生态系统对外界压力的适应性及遭受破坏的恢复力,开展生态敏感性评价是识别区域生态环境问题的有效手段之一。根据青藏高原的区域特性和主要生态环境问题,在定量构建土地荒漠化敏感性、水土流失敏感性、滑坡灾害敏感性和冻融侵蚀敏感性的基础上,通过空间距离指数法对青藏高原生态敏感性进行综合评价,并采用空间自相关分析和生态敏感性变化模式分析,探讨其时空演变特征和保护管理区划。结果表明：（1）青藏高原综合生态敏感性由西北向东南递减,极度和重度敏感区主要集中在西北部和高大山脉区,不敏感区主要集中在东南部;（2）2000-2018年间青藏高原综合生态敏感性指数值从1.49上升到1.51,表明该区域生态敏感性逐步下降,生态环境改善明显;（3）青藏高原生态敏感性存在显著的空间正相关,低-低聚集网格数量波动上升,从2000年的7277增至2018年7357,表明青藏高原部分地区的生态环境仍存在着一定恶化的风险;（4）根据区域生态敏感性变化模式分析,将青藏高原划分为严格保护区、生态退化区、潜在治理区、生态改善区和综合发展区五个区域,并提出了相应保护与管理对策。研究结果可以为青藏高原生态保护和可持续发展提供参考,从而有效推动保护管理措施的制定。     

Comparisons of high, medium, and low feedback sensitivity for the control of heart-rate acceleration

Thirty-four student volunteers were randomly assigned to one of three feedback sensitivity conditions: high sensitivity, medium sensitivity, or low sensitivity. Each subject received four sessions of biofeedback training with instructions to accelerate heart rate. In each condition, analogue feedback was provided during heart-rate acceleration trials. In addition to heart rate, frontal EMG and digital skin temperature were also recorded. Results replicated and extended the findings of a previous study in that medium and low sensitivity feedback was found to be superior to high sensitivity feedback during the final training session. These results confirm previous findings that a high sensitivity feedback produces very poor control of heart-rate acceleration. These data were discussed in terms of motor skills theory and in terms of possible effects of feedback sensitivity upon the motivation of subjects.     

Structural sensitivity of biological models revisited

Enhancing the predictive power of models in biology is a challenging issue. Among the major difficulties impeding model development and implementation are the sensitivity of outcomes to variations in model parameters, the problem of choosing of particular expressions for the parametrization of functional relations, and difficulties in validating models using laboratory data and/or field observations. In this paper, we revisit the phenomenon which is referred to as structural sensitivity of a model. Structural sensitivity arises as a result of the interplay between sensitivity of model outcomes to variations in parameters and sensitivity to the choice of model functions, and this can be somewhat of a bottleneck in improving the models predictive power. We provide a rigorous definition of structural sensitivity and we show how we can quantify the degree of sensitivity of a model based on the Hausdorff distance concept. We propose a simple semi-analytical test of structural sensitivity in an ODE modeling framework. Furthermore, we emphasize the importance of directly linking the variability of field/experimental data and model predictions, and we demonstrate a way of assessing the robustness of modeling predictions with respect to data sampling variability. As an insightful illustrative example, we test our sensitivity analysis methods on a chemostat predator-prey model, where we use laboratory data on the feeding of protozoa to parameterize the predator functional response.     

Comparative study of parameter sensitivity analyses of the TCR-activated Erk-MAPK signalling pathway

Parameter estimation is a major challenge for mathematical modelling of biological systems. Given the uncertainties associated with model parameters, it is important to understand how sensitive the model output is to variations in parameter values. A local sensitivity analysis determines the model sensitivity to parameter variations over a localised region around the nominal parameter values, whereas a global sensitivity analysis (GSA) investigates the sensitivity over the entire parameter space. Using a T-cell receptor-activated Erk-MAPK signalling pathway model as an example, the authors present a comparative study of a variety of different sensitivity analysis techniques. These techniques include: local sensitivity analysis, existing GSA methods of partial rank correlation coefficient, Sobol's, extended Fourier amplitude sensitivity test, as well as a weighted average of local sensitivities and a new GSA method to extract global parameter sensitivities from a parameter identification routine. Results of this study revealed critical reactions in the signalling pathway and their impact on the signalling dynamics and provided insights into embedded regulatory mechanisms such as feedback loops in the pathway. From this study, a recommendation emerges for a general sensitivity analysis strategy to efficiently and reliably infer quantitative, dynamic as well as topological properties from systems biology models.     

Effects of environment during growth on the sensitivity of leaf conductance to changes in humidity

Soybeans (Glycine max) and grain amaranth (Amaranthus hypochondriacus) were grown at a range of temperatures, carbon dioxide concentrations and light conditions in controlled environment chambers, and the response of leaf conductance to water vapour to changes in humidity was then measured under a standard set of conditions. The sensitivity of conductance was analysed in terms of (i) the absolute sensitivity of conductance to changes in leaf to air water vapour pressure difference (LAVPD), (ii) the sensitivity of conductance relative to the absolute value of conductance, and (iii) the slope of the relationship between conductance and an index incorporating assimilation rate, carbon dioxide concentration and relative humidity. The sensitivity of conductance varied substantially with growth conditions for all three analyses in both species. The growth temperature of 25 °C increased the sensitivity of conductance by all three measures compared with growth at 20 or 30 °C in amaranth, with little difference between 25 and 30 °C in soybean. Growth at elevated carbon dioxide decreased sensitivity in amaranth by all three measures, and decreased the absolute but not the relative sensitivity in soybean. Growth at reduced photon flux density and growth at high stand density reduced sensitivity in amaranth by all three measures. In soybean, growth at high stand density reduced sensitivity by all three measures, but growth at low photon flux density increased the relative sensitivity. The sensitivity of leaf conductance to changes in humidity varied by a factor of two or more with growth environment by all measures of sensitivity in both the C3 and the C4 species.     

Measurement of sensitivity to olfactory flavor: application in a study of aging and dentures

Olfaction involves a dual sensory process for perceiving odors orthonasally (through the nostrils) and retronasally (through the mouth). This investigation entailed developing a measure of sensitivity to an odor delivered in an orally sampled food (orange flavoring in a sucrose-sweetened gelatin) and examining sensitivity in the elderly. In experiment 1, olfactory flavor sensitivity was 49 times lower in elderly (n = 21) than in young (n = 28) subjects. In experiment 2, with 73 elderly women, higher olfactory flavor sensitivity correlated significantly with higher orthonasal perception (Connecticut Chemosensory Clinical Research Center test). Some women, however, exhibited low olfactory flavor sensitivity despite high orthonasal perception; none had high olfactory flavor sensitivity and low orthonasal perception. Those who wore complete or palatal covering dentures had lower olfactory flavor sensitivity than those who were dentate or wore dentures that did not cover the palate. Through multiple regression analysis, orthonasal perception and denture status were found to be independent contributors to predicting olfactory flavor sensitivity. In summary, elderly subjects showed depressed olfactory flavor sensitivity (i.e. retronasal sensitivity) that related to poor orthonasal olfactory perception and denture characteristic. Thus, while good orthonasal olfaction may be necessary for good olfactory flavor sensitivity, it is not sufficient. Other factors, some associated with oral conditions, may impede release and retronasal transport of odors from the mouth to the olfactory receptors.     

The effect of membrane-bound beta-lactamase on linoleic acid sensitivity in Staphylococcus aureus

The presence of a plasmid conferring resistance to penicillin (PC plasmid, e.g. pI258blaI-) in Staphylococcus aureus NCTC 8325 increases the sensitivity of such a bacterium to the growth inhibitory effects of linoleic acid, whereas a plasmid conferring resistance to tetracycline does not affect linoleic acid sensitivity. The increased linoleic acid sensitivity of bacteria containing a PC plasmid may be related to the penicillinase protein itself since (i) strains having inducible penicillinase show increased sensitivity only after induction, (ii) strains in which penicillinase is directed from chromosomal or plasmid-borne genes show similar increased linoleic acid sensitivity and (iii) notwithstanding the above, the linoleic acid inhibitory effect is enhanced in a strain in which penicillinase activity is greatly reduced by a point mutation in the structural gene for penicillinase. The enhanced linoleic acid sensitivity seems to require the membrane-bound penicillinase since added extracellular penicillinase does not confer this sensitivity, and there appears to be a specific interaction between the membrane-bound penicillinase activity and linoleic acid.     

基于空间距离指数的中国西北干旱内陆河流域生态敏感性时空演变特征——以石羊河流域为例

生态敏感性是生态系统对自然环境变化和人类活动干扰的反映程度及生态环境问题发生难易程度和可能性大小的重要因素之一。以中国西北地区典型的干旱内陆河流域-石羊河流域为例,通过借鉴前人研究成果及实地调查研究,将石羊河流域生态敏感性分为生态风险敏感性、水土流失敏感性和生物多样性敏感性三个方面,并系统构建生态风险敏感性指数、水土流失敏感性指数和生物多样性敏感性指数三个定量评价指标,对石羊河流域综合生态敏感性进行研究。并通过格网编码、圈层分析,探讨近30年石羊河流域生态敏感性的时空变化。研究结果表明:(1)1987—2016年间石羊河流域生态敏感性总体上逐年降低,综合生态敏感性指数(Comprehensive ecological sensitivity index,CESI)值从1987年的1.143上升到2016年的1.287,反映出流域生态环境当前还是向着可持续发展的方向发展;(2)流域生态敏感性整体偏高,常年极度敏感区和常年重度敏感区占流域总面积的42.26%。此外,敏感性空间分异明显,流域上游及下游荒漠区敏感性相对稳定,中下游绿洲区敏感性波动变化较为频繁,且波动变化区占总面积的51.24%,这表明流域生态敏感性与人类活动及工农业生产有较为密切的关系;(3)目前流域生态敏感性整体趋于好转,但局部地区有恶化的趋势,敏感性波动降低的区域面积为11693.57km~2,占流域总面积的28.82%,敏感性波动升高的区域面积为9099.66km~2,占流域总面积的22.43%,这表明一方面在国家宏观政策的引导下,当地在生态环境保护方面做了大量工作,另一方面也表现出在全球生态环境逐渐恶化的大背景下,当地的生态环境治理工作仍然任重道远。     

Breast imaging using 3D electrical impedence tomography

Aim: To determine the diagnostic efficiency of 3D Eletrical Impedance Tomography (EIT) compared to Mammography (MG) and Ultrasonography (USG) in imaging the breast. Materials and Methods: A group of 88 patients presenting with various breast complaints was examined using combined Mammography and Ultrasonography (MG & USG) or either of these modalities alone. The same patients were then examined using the 3D EIT imaging system "MEIK". The findings were then compared. The sensitivity of these modalities for this group of patients were later determined and statistically analysed. Results: Of the total of 88 patients, 59 findings were "suspicious" by any of the 3 modalities alone or by their combination. EIT had a sensitivity of 77.8 % compared to MG with a sensitivity of 83.3 % and USG with a sensitivity of 94.4 % regarding cases of fibrocystic mastitis. For cases involving cysts, EIT had 100 % sensitivity which was the same as that for USG compared to MG with a sensitivity of only 81 %. Among cases of fibroadenoma, EIT had a sensitivity of just 68.8 % compared to MG with a sensitivity of 87.5 % and USG with a sensitivity of 75 %. Finally among cases of carcinoma, EIT had a sensitivity of 75 % compared to the sensitivity of 100 % of MG and USG in our group of patients. The study revealed that there was no overall significant difference in sensitivity between MG-USG (p = 0.219) and MG-EIT (p = 0.779) and USG-EIT (p = 0.169). However, in regard to identifying cysts there was significant difference in the sensitivity of MG compared to USG & EIT suggesting that EIT has a role in these cases. Conclusion: Electrical impedance could be used as an adjunct to Mammography and Ultrasonography for breast cancer detection. However, the differentiation of malignant from benign lesions based on impedance measurements needs further investigation. Multifrequency electrical impedance imaging appears the most promising for detecting breast malignancies but methodological improvements need to be made to realise its potential.     

miR-181a is an intrinsic modulator of T cell sensitivity and selection

T cell sensitivity to antigen is intrinsically regulated during maturation to ensure proper development of immunity and tolerance, but how this is accomplished remains elusive. Here we show that increasing miR-181a expression in mature T cells augments the sensitivity to peptide antigens, while inhibiting miR-181a expression in the immature T cells reduces sensitivity and impairs both positive and negative selection. Moreover, quantitative regulation of T cell sensitivity by miR-181a enables mature T cells to recognize antagonists-the inhibitory peptide antigens-as agonists. These effects are in part achieved by the downregulation of multiple phosphatases, which leads to elevated steady-state levels of phosphorylated intermediates and a reduction of the T cell receptor signaling threshold. Importantly, higher miR-181a expression correlates with greater T cell sensitivity in immature T cells, suggesting that miR-181a acts as an intrinsic antigen sensitivity "rheostat" during T cell development.     

Organ culture of rat heart: maintained high sensitivity of fetal atria before innervation to norepinephrine

Changes in sensitivity to norepinephrine (NE) of fetal and neonatal rat right atria placed in organ culture were examined. The high sensitivity to NE of the 17-day fetal atria was maintained during organ culture for 5 days. The pD2 value for NE at the 17th day of gestation was 8.66 +/- 0.09, and that after organ culture for 5 days was 8.62 +/- 0.09. The sensitivity of 1-day-old neonatal artia was significantly lower than that of fetal atria; but when they were cultured for 24 h, there was a 10-fold increase in sensitivity. The pD2 value before culture was 7.59 +/- 0.05, and that after culture was 8.54 +/- 0.04. NE added to the culture medium prevented this increase in sensitivity. Similar changes were observed in the sensitivity to isoproterenol, but not in the sensitivity to forskolin, indicating that these sensitivity changes were of a postjunctional nature and most likely due to some changes in the beta-receptor and (or) its coupling to adenylate cyclase. Therefore, the decrease in myocardial sensitivity to NE observed during the late fetal period is most likely to be caused by factor(s) related to sympathetic innervation.     

OGTT-derived measures of insulin sensitivity are confounded by factors other than insulin sensitivity itself

Insulin resistance is an important risk factor for diabetes and other diseases. It has been important to estimate insulin resistance in epidemiological and genetic studies involving significant number of individuals. Complex and invasive protocols are impractical. Therefore, insulin sensitivity indices based on the oral glucose-tolerance test (OGTT) have been introduced. The aim of the present study was to assess the accuracy with which OGTT-derived indices would reflect changes in insulin sensitivity in the face of changes in other factors, such as rate of glucose absorption and/or B-cell function. A computer model was employed to predict excursions of plasma glucose and insulin after a 75-g oral glucose load. The model was then used to predict changes in these excursions, which would be observed with altered insulin resistance, with alterations in beta-cell sensitivity to glucose and/or alterations in glucose absorption rates. Published indices of insulin sensitivity could then be calculated from the predicted curves, to ask whether changes in beta-cell function or glucose absorptions rates might be misinterpreted (using the indices) as changes in insulin sensitivity. The model accurately represented OGTT data for a normal glucose tolerant subject, closely matching published data. Imposed 50% reductions or increases in insulin sensitivity alone in the model were reflected in only small changes in OGTT-derived insulin sensitivity values. More important, imposed alterations in beta-cell sensitivity and glucose absorption without simulated changes in insulin sensitivity did change insulin sensitivity indices. These results indicate that caution is required for the interpretation of differences in OGTT-derived values of insulin sensitivity, because variation in factors other than insulin sensitivity per se appear to have the greatest effects on indices calculated from the OGTT alone.     

Chronosensitivity to absolute hypercapnia in various light regimens

The studies of mice on the natural regimen of day and night alterations have revealed a daily rhythm of hypercapnia toxicity, with the maximum sensitivity observed at 6 a.m. and the minimum sensitivity at 6 p.m.-2 a.m. and 2 p.m.-6 p.m. The experiments on animals kept for 2 weeks-1 month on the constant light regimen have demonstrated the shift in sensitivity acrophase to 10 a.m.-4 p.m. and the prolongation of the daily period of increased sensitivity. With the animals' return to the natural regimen, a two-peak rhythm with the maximum sensitivity at 2 a.m. and 10 a.m.-2 p.m. and the minimum sensitivity at 22 p.m. and 6 a.m. was observed during the first 2 weeks-1 month. 2 months later the rhythm curve flattening was recorded, with the initial daily sensitivity rhythm to absolute hypercapnia recovering in 2 1/2 months.     

Nonverbal Communication and Human–Dog Interaction

Human–dog interaction relies to a large extent on nonverbal communication, and it is therefore plausible that human sensitivity to nonverbal signals affects interactions between human and dog. Experience with dogs is also likely to influence human–dog interactions, and it has been suggested that it influences human social skills. The present study investigated possible links between human nonverbal sensitivity, experience with dogs, and the quality of human–dog interactions. Two studies are reported. In study 1, 97 veterinary students took a psychometric test assessing human nonverbal sensitivity and answered a questionnaire on their experience with dogs. The data obtained were then used to investigate the relationship between experience with dogs and sensitivity to human nonverbal communication. The results did not indicate that experience with dogs improves human nonverbal sensitivity. In study 2, 16 students with high, and 15 students with low, levels of human nonverbal sensitivity were selected. Each of the 31 students interacted once with an unknown dog in a greeting situation, and these human–dog interactions were videoed. We found that a combined score of dog behaviors relating to insecurity was associated with the students' level of nonverbal sensitivity and experience with dogs: the dog showed more of the insecure behavior when interacting with students with a low level of nonverbal sensitivity and no experience with dogs than it did when interacting with students with a high level of nonverbal sensitivity (irrespective of experience with dogs).     

Role of short-chain saturated fatty acids in the control of ethylene sensitivity in senescing carnation flowers

In cut carnations ( Dianthus caryophyllus L. cv. Cally). petal senescence was associated with a climacteric pattern in ethylene production and an increase in ethylene sensitivity during the preclimacteric stage. The increase in ethylene sensitivity was caused by short-chain saturated fatty acids (C₇ to C₁₀) produced in the petals during the early stages of senescence. Pollination or application of octanoic acid to the styles of unpollinated flowers resulted in a sudden increase in ethylene sensitivity and a marked acceleration of senescence. Treatment with silver thiosulfate (STS) resulted in a suppression of ethylene sensitivity and a marked reduction in the levels of these fatty acids. However, even in STS-treated flowers pollination or treatment with octanoic acid gave rise to a drastic increase in ethylene sensitivity. Exposure of carnation flowers to 2. 5-norbornadicne (NBD) vapours resulted in a dramatic suppression of ethylene sensitivity which was also overridden by stylar application of octanoic acid. Exposure to NBD suppressed the increase in ethylene sensitivity caused by treatment with octanoic acid. It appears that short-chain saturated fatty acids increased ethylene sensitivity by increasing the ability of the tissue to bind ethylene.     

Dynamics of x-ray-induced reversion in heterogeneous S. cerevisiae populations.

The survival and frequency of adenine and homoserine revertants after X-irradiation have been studied in starved and growing populations of haploid S. cerevisiae (strain 5483/1b). A growing population is heterogeneous to cell killing, and a mathematical model can be used to determine possible correlation between sensitivity to killing and sensitivity to mutation induction. The results indicate correlation between sensitivity to ade2-1 reversion and sensitivity to cell killing, whereas no such correlation was found between sensitivity to hom3-10 reversion and sensitivity to killing. The difference in the dynamics of homoserine and adenine reversions was reduced by adding caffeine to the post-irradiation media.