Limiting Factors and Countermeasures for the Development of Biological Herbicides

This paper mainly analyzes the main limiting factors in the development of biological herbicides,such as narrow herbicidal spectrum,vulnerable to environmental impacts,difficulties in preparing dosage forms,difficult separation and low yield of active substances,biological safety,etc.Moreover,countermeasures and suggestions are put forward,including strengthening the study of biological screening of herbicidal activity,microbial metabolites and their use as lead compounds,dosage forms,fungi complex formulation,fungi and herbicide complex formulation,and fermentation technology.

Limiting climatic factors in shaping the distribution pattern and niche differentiation of Prunus dielsiana in subtropical China

Subtropical forest in China has received much attention due to its complex geologic environment and bioclimatic heterogeneity.There have been very few studies addressing which climatic factors have shaped both distribution patterns and niche differentiation of species from this region.It also remains unclear whether phylogenetic niche conservatism retains in plant species from this biodiversityrich subtropical region in China.In this study,we used geographic occurrence records and bioclimatic factors of Prunus dielsiana(Rosaceae),a wild cherry species,combined with the classical ENM-based DIVA-GIS software to access contemporary distribution and richness patterns of its natural populations.The current distribution of P.dielsiana occupied a relatively wide range but exhibited an uneven pattern eastward in general,and the core distribution zone of its populations are projected to concentrate in the Wushan and Wuling Mountain ranges of western China.Hydrothermic variables,particularly the Temperature Seasonality(bio4)are screened out quantitatively to be the most influential factors that have shaped the current geographical patterns of P.dielsiana.By comparison with other sympatric families,climatic niche at regional scale showed a pattern of phylogenetic niche conservatism within cherry species of Ros aceae.The effect of habitat filtering from altitude is more significant than those of longitude and latitude.We conclude that habitat filtering dominated by limiting hydrothermic factors is the primary driving process of the diversity pattern of P.dielsiana in subtropical China.

Attitudes, Practices and Factors Affecting the Use of the Partogram by Professionals Attending to Women in Labour and Delivery in the Bafut Health District

Introduction: Given that the provision of care to the childbirth process is not purely in the hands of educated and trained midwives, the competency in application of midwifery tools may be inadequate and consequently affect the quality of care. The Partogram is the single most important tool which has been scientifically proven to reduce maternal and foetal morbidity and mortality. Though important, many healthcare providers do not use it regularly in the monitoring of labour. Objectives: Our objectives were to determine the attitudes, practices, proportion of parturients monitored using a Partogram and the factors limiting the use of the Partogram by professionals attending to women in labour and delivery (PAWLD) in the Bafut Health District. Methods: This was a cross-sectional study carried out amongst 65 Professionals attending to women in labour and delivery in the Bafut Health District that lasted 6 months. All the data were collected by our self. First through a face to face interview with a questionnaire, secondly with an observational guide used to assess Partograms filled and lastly using delivery registers to obtain the proportion of parturients monitored with a Partogram. The data analysis was done using the statistic software Epi Info version 7 and Microsoft Excel. Results: This study revealed that 47 (72.3%) of participants had good attitudes, 34 (52%) had good practices, 375 (79.3%) parturients were monitored using a Partogram, and the lack of in-service training, low number of staff and poor knowledge on Partogram use were identified as the main limiting factors to the use of the Partogram. Being a health assistant was statistically significantly associated with having a poor practice with a p-value of 0.047 and odds ratio 5.33 [1.03 - 26.45] we obtained just 1 (1.54%) filled according to the WHO standards. Conclusions and Recommendations: In the Bafut Health District, 7 out of 10 PAWLDs have a positive attitude towards the use of the Partogram, while a poor practice is predominant as a result 4 out of 5 deliveries were monitored using a Partogram with only 1.54% of the Partograms filled according to WHO standards. The lack of in-service training, lack of PAWLD and poor knowledge on Partogram usage are the major drawbacks to the use of the Partogram. We therefore recommend that continues medical education (CME) be organised on the use of the Partogram.

Discussion on the limit recovery factor of carbon dioxide flooding in a permanent sequestration scenario

Based on practices of CO_(2) flooding tests in China and abroad,the recovery factor of carbon dioxide capture,utilization in displacing oil and storage(CCUS-EOR)in permanent sequestration scenario has been investigated in this work.Under the background of carbon neutrality,carbon dioxide injection into geological bodies should pursue the goal of permanent sequestration for effective carbon emission reduction.Hence,CCUS-EOR is an ultimate development method for oil reservoirs to maximize oil recovery.The limit recovery factor of CCUS-EOR development mode is put forward,the connotation differences between it and ultimate recovery factor and economically reasonable recovery factor are clarified.It is concluded that limit recovery factor is achievable with mature supporting technical base for the whole process of CCUS-EOR.Based on statistics of practical data of CO_(2) flooding projects in China and abroad such as North H79 block CO_(2) flooding pilot test at small well spacing in Jilin Oilfield etc.,the empirical relationship between the oil recovery factor of miscible CO_(2) flooding and cumulative CO_(2) volume injected is obtained by regression.Combined with the concept of oil production rate multiplier of gas flooding,a reservoir engineering method calculating CO_(2) flooding recovery factor under any miscible degree is established by derivation.It is found that when the cumulative CO_(2) volume injected is 1.5 times the hydrocarbon pore volume(HCPV),the relative deviation and the absolute difference between the recovery percentage and the limit recovery factor are less than 5%and less than 2.0 percentage points respectively.The limit recovery factor of CCUS-EOR can only be approached by large pore volume(PV)injection based on the technology of expanding swept volume.It needs to be realized from three aspects:large PV injection scheme design,enhancing miscibility degree and continuously expanding swept volume of injected CO_(2).

Plant hormesis and Shelford’s tolerance law curve

Shelford’s law of tolerance is illustrated by a bell-shaped curve depicting the relationship between environmental factor/factors’intensity and its favorability for species or populations.It is a fundamental basis of ecology when considering the regularities of environment impacts on living systems,and applies in plant biology,agriculture and forestry to manage resistance to environmental limiting factors and to enhance productivity.In recent years,the concept of hormesis has been increasingly used to study the dose-response relationships in living organisms of different complexities,including plants.This requires the need for an analysis of the relationships between the hormetic dose-response model and the classical understanding of plant reactions to environments in terms of Shelford’s law of tolerance.This paper analyses various dimensions of the relationships between the hormetic model and Shelford’s tolerance law curve under the influence of natural environmental factors on plants,which are limiting for plants both in deficiency and excess.The analysis has shown that Shelford’s curve and hormetic model do not contradict but instead complement each other.The hormetic response of plants is localized in the stress zone of the Shelford’s curve when adaptive mechanisms are disabled within the ecological optimum.At the same time,in a species range,the ecological optimum is the most favorable combination of all or at least the most important environmental factors,each of which usually deviates slightly from its optimal value.Adaptive mechanisms cannot be completely disabled in the optimum,and hormesis covers optimum and stress zones.Hormesis can modify the plant tolerance range to environmental factors by preconditioning and makes limits of plant tolerance to environmental factors flexible to a certain extent.In turn,as a result of tolerance range evolution,quantitative characteristics of hormesis(width and magnitude of hormetic zone)as well as the range of stimulating doses,may significantly differ in various plant species and even populations and intra-population groups,including plants at different development stages.Using hormetic preconditioning for managing plant resistance to environmental limiting factors provides an important perspective for increasing the productivity of woody plants in forestry.

Finite element analysis of slope stability by expanding the mobilized principal stress Mohr's circles-Development, encoding and validation

In recent years,finite element analysis is increasingly being proposed in slope stability problems as a competitive method to traditional limit equilibrium methods(LEMs)which are known for their inherent deficiencies.However,the application of finite element method(FEM)to slope stability as a strength reduction method(SRM)or as finite element limit analysis(FELA)is not always a success for the drawbacks that characterize both methods.To increase the performance of finite element analysis in this problem,a new approach is proposed in this paper.It consists in gradually expanding the mobilized stress Mohr’s circles until the soil failure occurs according to a prescribed non-convergence criterion.The present approach called stress deviator increasing method(SDIM)is considered rigorous for three main reasons.Firstly,it preserves the definition of the factor of safety(FOS)as the ratio of soil shear strength to the mobilized shear stress.Secondly,it maintains the progressive development of shear stress resulting from the increase in the principal stress deviator on the same plane,on which the shear strength takes place.Thirdly,by introducing the concept of equivalent stress loading,the resulting trial stresses are checked against the violation of the actual yield criterion formed with the real strength parameters rather than those reduced by a trial factor.The new numerical procedure was encoded in a Fortran computer code called S^(4)DINA and verified by several examples.Comparisons with other numerical methods such as the SRM,gravity increasing method(GIM)or even FELA by assessing both the FOS and contours of equivalent plastic strains showed promising results.