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1.
The addition of a limit to the drought factor used it the equations describing the McArthur forest fire danger meter Mark 5 gives an improved estimation of forest fire behaviour.  相似文献   

2.
In situ optical meters are widely used to estimate leaf chlorophyll concentration, but non‐uniform chlorophyll distribution causes optical measurements to vary widely among species for the same chlorophyll concentration. Over 30 studies have sought to quantify the in situ/in vitro (optical/absolute) relationship, but neither chlorophyll extraction nor measurement techniques for in vitro analysis have been consistent among studies. Here we: (1) review standard procedures for measurement of chlorophyll; (2) estimate the error associated with non‐standard procedures; and (3) implement the most accurate methods to provide equations for conversion of optical to absolute chlorophyll for 22 species grown in multiple environments. Tests of five Minolta (model SPAD‐502) and 25 Opti‐Sciences (model CCM‐200) meters, manufactured from 1992 to 2013, indicate that differences among replicate models are less than 5%. We thus developed equations for converting between units from these meter types. There was no significant effect of environment on the optical/absolute chlorophyll relationship. We derive the theoretical relationship between optical transmission ratios and absolute chlorophyll concentration and show how non‐uniform distribution among species causes a variable, non‐linear response. These results link in situ optical measurements with in vitro chlorophyll concentration and provide insight to strategies for radiation capture among diverse species.  相似文献   

3.
树木花期预报在林果、养蜂、园林和旅游业等方面有很大的实用价值。该文以大山樱(Prunus sargentii)为例,探讨通过花芽形态测量进行花期预报的新方法。通过1998~2000年对北京玉渊潭公园大山樱进行的数据采集和处理,建立了线性和指数两种预报模型。2002年的试报检验表明,采用3株的观测数据,并利用3日滑动平均的方法,对观测数据进行处理后所作的预报,误差在3 d以内的预报达80%以上;2003年连续测报的平均误差,模型1为1.6 d,模型2为2.1 d。这一树木花期预报的物候学新方法,简便易行、建模周期短、预报精度高,在春季芽膨大后,直至露瓣期之前,可以逐日连续发布预报。  相似文献   

4.
The degree of grass curing, i.e. the proportion of dehydrated dead grass per unit grassland area, is one of the most important parameters affecting grassland fire risk and fire behaviour. The objective of the present study was to develop a simple relationship between grass moisture and grass curing to use as an input into the next-generation fire-danger rating models of the Deutscher Wetterdienst. Seasonal changes in yellow and green portions of grass plots were estimated visually at weekly intervals. At the same time, the grass-moisture content was measured gravimetrically after destructive sampling. Regression analysis revealed an exponential relationship between decreasing leaf moisture and increasing yellowing level, in rough agreement with findings reported from Australia and North America.  相似文献   

5.
Near-term freshwater forecasts, defined as sub-daily to decadal future predictions of a freshwater variable with quantified uncertainty, are urgently needed to improve water quality management as freshwater ecosystems exhibit greater variability due to global change. Shifting baselines in freshwater ecosystems due to land use and climate change prevent managers from relying on historical averages for predicting future conditions, necessitating near-term forecasts to mitigate freshwater risks to human health and safety (e.g., flash floods, harmful algal blooms) and ecosystem services (e.g., water-related recreation and tourism). To assess the current state of freshwater forecasting and identify opportunities for future progress, we synthesized freshwater forecasting papers published in the past 5 years. We found that freshwater forecasting is currently dominated by near-term forecasts of water quantity and that near-term water quality forecasts are fewer in number and in the early stages of development (i.e., non-operational) despite their potential as important preemptive decision support tools. We contend that more freshwater quality forecasts are critically needed and that near-term water quality forecasting is poised to make substantial advances based on examples of recent progress in forecasting methodology, workflows, and end-user engagement. For example, current water quality forecasting systems can predict water temperature, dissolved oxygen, and algal bloom/toxin events 5 days ahead with reasonable accuracy. Continued progress in freshwater quality forecasting will be greatly accelerated by adapting tools and approaches from freshwater quantity forecasting (e.g., machine learning modeling methods). In addition, future development of effective operational freshwater quality forecasts will require substantive engagement of end users throughout the forecast process, funding, and training opportunities. Looking ahead, near-term forecasting provides a hopeful future for freshwater management in the face of increased variability and risk due to global change, and we encourage the freshwater scientific community to incorporate forecasting approaches in water quality research and management.  相似文献   

6.
Huang M  Ma Y  Wan J  Zhang H  Wang Y  Chen Y  Yoo C  Guo W 《Bioresource technology》2011,102(19):8907-8913
A hybrid artificial neural network - genetic algorithm numerical technique was successfully developed to model, and to simulate the biodegradation process of di-n-butyl phthalate in an anaerobic/anoxic/oxic (AAO) system. The fate of DnBP was investigated, and a removal kinetic model including sorption and biodegradation was formulated. To correlate the experimental data with available models or some modified empirical equations, the steady state model equations describing the biodegradation process have been solved using genetic algorithm (GA) and artificial neural network (ANN) from the water quality characteristic parameters. Compared with the kinetic model, the performance of the GA-ANN for modeling the DnBP was found to be more impressive. The results show that the predicted values well fit measured concentrations, which was also supported by the relatively low RMSE (0.2724), MAPE (3.6137) and MSE (0.0742)and very high R (0.9859) values, and which illustrates the GA-ANN model predicting effluent DnBP more accurately than the mechanism model forecasting.  相似文献   

7.
山西闻喜早更新世的哺乳动物化石发现并不十分丰富,由于地层出露较好,层位清楚,虽然地层较薄,但对确定早更新世,为今后进一步深入研究汾渭盆地的第四纪下限,古气候、古地理环境可提供依据。  相似文献   

8.
1. Under laboratory conditions Limulus from 20 to 60 mm. in diameter are positively phototropic, and execute circus movements towards the normal side, when the median and the opposite lateral eyes are removed or covered. 2. The phototropism of Limulus may be modified or obliterated by (a) fright, (b) hunger, (c) stereotropism, (d) photokinesis, and (e) unknown stimuli. 3. Quantitative measurements of the paths of animals doing circus movements demonstrate that the amount of turning varies directly with the light intensity as follows: for 8,000 candle meters the degrees turned per centimeter were 6.73; for 2,000 candle meters, 5.23; and for 900 candle meters, 4.78. In other words, the diameter of the circle varies inversely with the light intensity. 4. The rate of locomotion per minute also varies directly with the light intensity, being 178 cm. for 8,000 candle meters, 167 for 2,000, and 157 for 900. 5. These reactions are satisfactorily explained by the tropism theory.  相似文献   

9.
《Journal of neurochemistry》2018,144(2):112-114
The 2016 Mark Smith Award winner is Sunmin Jung (Seoul National University), for the pa per Dual‐specificity phosphatase 26 (DUSP26) stimulates Aβ42 generation by promoting amyloid precursor protein axonal transport during hypoxia . Journal of Neurochemistry (2016) 137(5): 770‐781, Sunmin Jung, Jihoon Nah, Jonghee Han, Seon‐Guk Choi, Hyunjoo Kim, Jaesang Park, Ha‐Kyung Pyo, Yong‐Keun Jung. https://doi.org/10.1111/jnc.13597  相似文献   

10.
This paper studies the effectiveness of a class of linear statistical estimators called autoregressive and autoregressive-moving averages equations for mimicking and predicting the abundance fluctuations of three species of Drosophila censused at a pine plantation near Bogota, Colombia. A short introductory justification for the use of linear estimators is given followed by a brief discussion of the theoretical basis of statistical prediction. The assumptions of the method, fitting techniques, and use of the equations in forecasting are discussed. The mimicking ability of the equations is tested by comparing monte carlo simulations employing the fitted models to the observed fluctuations of the three species. Of the autoregressive equations fitted to each species two are judged successful and one less than successful. Autoregressive-moving averages models were found to be significantly worse predictors than the simpler autoregressive equations for these three species. The parameter estimates given by the preliminary estimation techniques are compared with the statistically efficient least squares estimates. The estimates compare well for most of the autoregressive models, but the parameter estimates for the autoregressive-moving averages models were misleading.  相似文献   

11.
Skene L 《Bioethics》1991,5(2):113-117
In a preceding article, Mark Wicclair suggested that where patient preferences clash with the doctor's recommendations, a minimal understanding of the task at hand, rather than the risks involved, should be the basis for standards of patient competence in decision-making (Bioethics 5(2):91-104, April 1991). Skene, Principal Law Reform Officer of the Victoria, Australia, Law Reform Commission, questions Wicclair's minimum standard from a legal standpoint, pointing out contradictions in the effects of such a standard. Skene concludes that legal protection and the education of both doctors and patients are the most suitable safeguards of patient autonomy.  相似文献   

12.
Focusing on one family from a study of dual-earner middle-class families carried out in Los Angeles, California, this article draws on interview and video-recorded data of everyday interactions to explore illness and healing as embedded in the microcultural context of the Morris family. For this family, an important aspect of what is at stake for them in their daily lives is best understood by focusing on 9-year-old Mark, who has been diagnosed with attention-deficit/hyperactivity disorder (ADHD). In this article, we grapple with the complexity of conveying some sense of how Mark’s condition is experienced and relationally enacted in everyday contexts. Through illuminating connections between lives as lived and lives as told, we explore the narrative structuring of healing in relation to Mark’s local moral world with the family at its center. We examine how his parents understand the moral consequences of the child’s past for his present and future, and work to encourage others to give due weight to his troubled beginnings before this child joined the Morris family. At the same time, we see how the Morris parents act to structure Mark’s moral experience and orient to a desired future in which Mark’s “success” includes an appreciation of how he is accountable to others for his actions. Through our analyses, we also seek to contribute to discussions on what is at stake in everyday life contexts for children with ADHD and their families, through illuminating aspects of the cultural, moral and relational terrain that U.S. families navigate in contending with a child’s diagnosis of ADHD. Further, given that ADHD is often construed as a “disorder of volition,” we seek to advance anthropological theorizing about the will in situations where volitional control over behavior is seen to be disordered.  相似文献   

13.
目的探讨谷氨酰胺对急进高原大鼠小肠黏膜形态结构及肠道微生态的影响。方法W istar大鼠50只,随机分为5组:对照组(A组)、3848米未干预组(B组)、3848米谷氨酰胺干预组(C组)、4767米未干预组(D组)和4767米谷氨酰胺干预组(E组),每组10只,急进海拔3848米和4767米造成大鼠急性缺氧模型,检测小肠黏膜上皮细胞形态结构、肠道菌群失衡及细菌易位的变化。结果高海拔缺氧组大鼠小肠黏膜变薄、肠黏膜水肿、绒毛短缩,肠道菌群失衡显著高于对照组(P0.05),且随着海拔升高,菌群失衡更明显。不同海拔高度细菌易位率也有差异。经谷氨酰胺干预后,肠道的菌群失衡及细菌易位率与高海拔缺氧组比较差异有显著性(P0.05)。结论急进高原缺氧环境可导致小肠黏膜损伤、肠道菌群失衡及细菌易位,肠黏膜屏障破坏,且随着海拔升高而上述改变更明显。谷氨酰胺具有保护肠黏膜屏障及调节肠道菌群失衡的作用。  相似文献   

14.
The 5-jump test (5JT) was proposed to evaluate lower limb explosive power of athletes competing in various disciplines. Although 5JT performance is usually expressed in absolute terms as the overall distance covered (i.e., in meters), subject size can play a significant role in the performance. The aims of the present study were to test the relationship of 5JT absolute performance with laboratory tests for explosive power and to develop performance notations useful to improve the diagnostic value of 5JT. Fifteen elite soccer players, members of the Under-23 Tunisian national team, were tested for 5JT, force platform vertical jumping (squat jump [SJ] and arm-aided countermovement jump [Arm-CMJ]), and concentric isokinetic leg extension/flexion (90 degrees x s(-1) and 240 degrees x s(-1)). 5JT performance was expressed in absolute terms (meters), relative to leg length (5JT-relative) and with body mass-dependent notations (Body mass x 5JT, 5JT-body mass). 5JT performance was significantly correlated with SJ height and scaled (W x kg) peak power (0.72 and 0.77, respectively, p < 0.01). 5JT-relative values were significantly related to SJ and Arm-CMJ height (0.61 and 0.71, respectively, p < 0.05) and scaled peak power (0.57 and 0.59, respectively, p < 0.05). 5JT-body mass revealed significantly related of SJ (0.82, p < 0.0001) and Arm-CMJ peak power (0.54, p < 0.05) and to SJ and Arm-CMJ peak force (0.67 and 0.65, respectively p < 0.05). 5JT-relative and 5JT-body mass correlated significantly with knee extensors 240 degrees x s(-1) (0.60, p < 0.05) and knee flexors 90 degrees x s(-1) (0.67, p < 0.01) isokinetic acceleration time, respectively. The results of this study suggest that the 5JT may be regarded as an explosive strength diagnostic tool under field conditions in elite soccer players. The use of performance notation accounting for body size differences may improve the diagnostic ability of 5JT.  相似文献   

15.
利用周期分析法预测稻纵卷叶螟的发生程度   总被引:7,自引:1,他引:7  
陈观浩 《昆虫知识》2004,41(3):258-260
根据化州市早稻稻纵卷叶螟CnaphalocrocismedinalisGuenee主害代的历年发生程度资料 ,采用方差分析方法寻找其显著周期 ,并提取其周期数组 ,重复这一过程 ,直到没有显著周期时为止 ,共提取出2个显著周期的周期数组。将这些周期数组外延和叠加后 ,进行拟合检验 ,结果表明 ,周期分析方法适用于拟合并预测化州市稻纵卷叶螟发生的年变化情况。于是对该市早稻稻纵卷叶螟发生程度进行了多年预测 ,其中最初 3年的预测结果已得到证实 ,表明用周期分析方法进行预测是可行的  相似文献   

16.
Tsortos A  Papadakis G  Gizeli E 《Biopolymers》2011,95(12):824-832
We measured the intrinsic viscosity of very small synthetic DNA molecules, of 20-395 base pairs, and incorporated them in a nearly complete picture for the whole span of molecular weights reported in the literature to date. A major transition is observed at M approximately 2 × 10(6) . It is found that in the range of approximately 7 × 10(3) ≤ M ≤ 2 × 10(6) , the intrinsic viscosity scales as [η] approximately M(1.05) , suggesting that short DNA chains are not as rigid as generally thought. The corresponding scaling for the range of 2 × 10(6) ≤ M ≤ 8 × 10(10) is [η] approximately M(0.69) . A comparison of our results with existing equations, for much narrower data distributions, is made, and the agreement is very satisfactory considering the huge range of data analyzed here. Experimental concerns such as the effect of ionic strength, polydispersity, temperature, and shear rate are discussed in detail. Some issues concerning the Huggins coefficient, polymer chain stiffness, and the relationship between the Mark-Houwink constants K, α are also presented; it is found that log K = 1.156 - 6.19α.  相似文献   

17.
从福建梅花山自然保护区海拔450m和1 200m的常绿阔叶林中选取17种常绿乔、灌木,对其叶片虫食状和取食强度进行分析,结果如下:(1)17种植物叶片共有15种虫食状类型,每种叶片虫食状类型为8~14;虫食状出现频率0.02%~37.01%,其中缘食状出现频率最高(37.01%),叶中脉食状出现频率最低(0.02%)。(2)木荷(Schima superba)的取食强度最大(9.60%),栲树(Castanopsis fargesii)次之(6.61%),油茶(Camellia Oleifera)最小(0.34%)。(3)15种虫食状类型中有6对虫食状呈显著正相关,2对呈显著负相关。(4)海拔1 200m处的甜槠(Castanopsis eyrei)、木荷、栲树和连蕊茶(Camellia fraterna)比海拔450m处的同种植物叶片的虫食强度高,其中木荷差异最大,从13.81%降至2.93%。  相似文献   

18.
本研究主要探讨黄龙自然保护区森林生态系统年净初级生产力水平和栖息地复杂程度对小型兽类物种多样性的影响。将调查区按海拔高度分为4 个调查点,每点的年净初级生产力水平各不相同,分别为: 24.9 MJ / (m2·a) ; 21.5 MJ / (m2·a) ; 17.5 MJ / (m2·a) 和14.1 MJ / (m2·a) 。在选择调查点时,同时考虑栖息地复杂程度,在生产力水平较高的调查点选择栖息地复杂程度较低的地点,而在生产力较低的调查点选择栖息地复杂程度较高的地点调查,以便分析森林生态系统年净初级生产力水平与栖息地复杂程度对小型兽类物种多样性的影响。采用鼠铗捕获小型兽类。结果表明,小型兽类物种多样性与森林生态系统年净初级生产力水平有密切关系,随着海拔升高,森林生态系统年净初级生产力的降低,所捕获的小型兽类生物量随之降低,其物种多样性也随之下降。小型兽类物种多样性也与栖息地复杂程度有关,森林生态系统年净初级生产力水平在一定范围内,大于17.5 MJ / (m2·a) ,栖息地复杂度的增加可以降低年净初级生产力水平对小型兽类物种多样性的影响。然而,森林生态系统年净初级生产力水平降低到一定程度时,小于14.1 MJ / (m2·a) ,生产力水平则为影响小型兽类物种多样性的主要因子。此外,小型兽类的生物量与森林生态系统年净初级生产力和栖息地复杂程度也有类似的关系。  相似文献   

19.
Toxocity of ampicillin trihydrate was studied in acute and chronic experiments. It was shown that the antibiotic had low acute toxicity, did not cumulate and had no skin-irritating effect. On its inhalation in concentrations of 5 mg/m3 for 4 months, ampicillin induced allergization of albino rats, decreased their immunity. The general toxic effect of the drug was slightly pronounced. Ampicillin in a concentration of 0.1 mg/m3 induced tension of the immunological reactivity of the organism. The maximum permissible concentration (MPC) of ampicillin in the working premises equal to 0.1 mg/m3 is recommended. Mark "Allergen" is necessary.  相似文献   

20.
Dr. Mark Cockett is Vice President of Infectious Diseases and Applied Genomics at Bristol-Myers Squibb (BMS). In this interview, we ask Dr. Cockett about considerations that major pharmaceutical companies such as BMS make when screening for and developing antiviral small molecule therapeutics. We discuss the rationale behind an unbiased screening approach that led to recent published work identifying a hepatitis C-specific NS5A inhibitor. We conclude by asking about the emerging role of academia in antiviral drug discovery and future directions of pathogen drug discovery in general.  相似文献   

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