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Strigolactones are a new-defined class of plant hormones which inhibit shoot branching and mediate the interaction of plant-AM fungi and plant-parasitic weeds

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Science China(Life Sciences) 2009年第8期52卷 693-700页

作者： ZAITLIN david Kentucky Tobacco Research and Development Center (KTRDC) University of Kentucky

Because plants are sessile organisms,the ability to adapt to a wide range of environmental conditions is critical for their *** a consequence,plants use hormones to regulate growth,mitigate biotic and abiotic stresses,and to communicate with other *** plant hormones function plei-otropically in vivo,and often work in tandem with other hormones that are chemically distinct.A newly-defined class of plant hormones,the strigolactones,cooperate with auxins and cytokinins to control shoot branching and the outgrowth of lateral *** were originally identified as compounds that stimulated the germination of parasitic plant seeds,and were also demonstrated to induce hyphal branching in arbuscular mycorrhizal(AM) *** fungi form symbioses with higher plant roots and mainly facilitate the absorption of phosphate from the *** to the classical definition of a plant hormone,strigolactones are produced in the roots and translocated to the shoots where they inhibit shoot outgrowth and *** biosynthesis of this class of compounds is regulated by soil nutrient availability,*** plant will increase its production of strigolactones when the soil phosphate concentration is limited,and decrease production when phosphates are in ample *** that affect plant shoot branching,AM fungal hyphal branching,and seed germination in parasitic plants facilitate chemical synthesis of similar compounds to control these and other biological processes by exogenous application.

关键词： strigolactone shoot branching AM symbioses parasitic weed

Factors influencing mercury accumulation in three species of forage fish from Caddo Lake, Texas, USA

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Journal of Environmental Sciences 2010年第8期22卷 1158-1163页

作者： Matthew M Chumchal Ray W Drenner david R Cross K david Hambright Department of Biology Texas Christian University 2800 S. University Dr Department of Psychology Texas Christian University 2800 S. University Dr Program in Ecology and Evolutionary Biology Biological Station and Department of Zoology 730 Van Vleet Oval University of Oklahoma

Most studies that have examined mercury （Hg） contamination of fish have focused on game species feeding near the top of the food web, while studies that examine forage fish that feed near the base of the food web are rare. We conducted a survey of Hg contamination in three species of forage fish, brook silverside （Labidesthes sicculus）, threadfin shad （Dorosoma petenense） and gizzard shad （Dorosoma cepedianum）, from Caddo Lake, Texas, USA and found species-specific differences in Hg concentrations. We examined total length, age, trophic position （determined using δ15N）, and growth rate of forage fish as factors that could have influenced within-and between-species differences in Hg concentration. Total length and age were the best predictors of within-species differences in Hg concentration. Between-species differences in Hg concentrations were most strongly influenced by trophic position.

关键词： mercury trophic position forage fish

Population-influenced spatiotemporal pattern of natural disaster and social crisis in China, AD1–1910

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Science China Earth Sciences 2019年第7期62卷 1138-1150页

作者： Shengda ZHANG david Dian ZHANG Department of Geography The University of Hong Kong School of Geographical Sciences Guangzhou University

Researchers mostly ascribe contemporary natural disaster and the concomitant social crisis to anomalous climate change or global warming. However, whether such a relationship is still valid in long-term historical settings remains doubtful. In this study, data obtained from historical records about natural calamities(flood and drought) and their social impacts(famine,cannibalism, and war) at provincial and decadal scales during AD1–1910 are applied to mathematical statistics such as correlation and regression analysis as well as spatial visualization. Also, the role of population in the nexus of meteorological catastrophes and human miseries is investigated. Results show that at the provincial scale, generally there is high consistency among different variables and most of them are clustered in eastern part of China, especially in the north. More in-depth examinations indicate regional disparities that variables account for higher proportion in the south during the later imperial era,which may be attributed to the southward movement of population center. At the decadal scale, drought is the primary contributor to famine and cannibalism, while severe or even out-of-control famine i.e. cannibalism is more likely to incur war than ordinary famine per se. Besides, population growth rate exerts its positive effect on natural hazards and food crises, whereas more wars bring population loss and relieve population stress despite the weak negative association. These findings supplement previous views and confirm that the distributions of disasters in ancient China are affected by population rather than climatic variability, which only determines the occurrence of disaster.

关键词： Natural disaster Social crisis Population Spatiotemporal pattern Historical China

Long-term changes in the plant ecology of an African savanna landscape and the implications for ecosystem theory and conservation management

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Ecological Processes 2021年第1期10卷 213-224页

作者： david Western Victor N.Mose david Maitumo Caroline Mburu African Conservation Centre P.O.Box 15289-00509NairobiKeny

Background:Studies of the African savannas have used national parks to test ecological theories of natural ecosystems,including equilibrium,non-equilibrium,complex adaptive systems,and the role of top-down and bottom-up physical and biotic *** such studies have excluded the impact of pastoralists in shaping grassland ecosystems and,over the last half century,the growing human impact on the world’s *** mounting human impact calls for selecting indicators and integrated monitoring methods able to track ecosystem changes and the role of natural and human *** study draws on five decades of monitoring the Amboseli landscape in southern Kenya to document the declining role of natural agencies in shaping plant ecology with rising human ***:We show that plant diversity and productivity have declined,biomass turnover has increased in response to a downsizing of mean plant size,and that ecological resilience has declined with the rising probability of extreme shortfalls in pasture *** signature of rainfall and physical agencies in driving ecosystem properties has decreased sharply with growing human *** compare the Amboseli findings to the long-term studies of Kruger and Serengeti national parks to show that the human influence,whether by design or default,is increasingly shaping the ecology of savanna *** look at the findings in the larger perspective of human impact on African grasslands and the world rangelands,in general,and discuss the implications for ecosystem theory and conservation policy and ***:The Amboseli study shows the value of using long-term integrated ecological monitoring to track the spatial and temporal changes in the species composition,structure,and function of rangeland ecosystems and the role of natural and human agencies in the process of *** study echoes the widespread changes underway across African savannas and world’s rangelands,concluding that some level

关键词： Savannas Plants Human dominance Macroecology Conservation

Maximizing the Delivery of MPR Broadcasting Under Realistic Physical Layer Assumptions

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Journal of Computer Science & Technology 2008年第3期23卷 451-460页

作者： Francois Ingelrest david Simplot-Ryl LCAV EPFLCH-1015LausanneSwitzerland IRCICA/LIFL CNRS UMR 8022Univ.Lille 1INRIA Lille-Nord EuropeFrance

It is now commonly accepted that the unit disk graph used to model the physical layer in wireless networks does not reflect real radio transmissions, and that a more realistic model should be considered for experimental simulations. Previous work on realistic scenarios has been focused on unicast, however broadcast requirements are fundamentally different and cannot be derived from the unicast case. Therefore, the broadcast protocols must be adapted in order to still be efficient under realistic assumptions. In this paper, we study the well-known multipoint relay broadcast protocol （MPR）, in which each node has to choose a set of 1-hop neighbors to act as relays in order to cover the whole 2-hop neighborhood. We give experimental results showing that the original strategy used to select these multipoint relays does not suit a realistic model. On the basis of these results, we propose new selection strategies solely based on link quality. One of the key aspects of our solutions is that our strategies do not require any additional hardware and may be implemented at the application layer, which is particularly relevant to the context of ad hoc and sensor networks where energy savings are mandatory. We finally provide new experimental results that demonstrate the superiority of our strategies under realistic physical assumptions.

关键词： ad hoc network multipoint relay broadcasting realistic physical layer sensor network

Computational and experimental study on corrosion inhibition potential of the synergistic 1:1 combination of Arabic and cashew gums on mild steel

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Petroleum Research 2020年第2期5卷 170-180页

作者： david Ebuka Arthur Department of Chemistry Base UniversityAbujaNigeria

The synergistic study of Acacia Senegal (arabic gum) and Anacardium occidentale (cashew gum) combination in corrosion inhibition of mild steel was carried out to determine the inhibition efficiency of their combination. The gums were purified using standard methods and the blend prepared using the method as described by Femi – Oyewo et al. The blend was then used for corrosion study at two temperatures (303 K and 333 K) and the corrosion rates calculated. The adsorption process was found to satisfy the Langmuir isotherm and hence the sorption study reveals that the interaction is a physical one since the free energy of adsorption (ΔG^(o) ads kJ/mol) is given as (−16.47 and −15.61) kJ/mol at temperature T = 303 K and 333K accordingly. The GCMS technique was used to characterize the blend, five chemical compounds and their area percentage [6-O-(1-L-maloyl)-alpha-,beta-D-Glcp (veracylglucan A) (22.11%), 6-Octadecanoic acid (55.76%), Methylhexadecanoate (3.97%), 1-Pentadecane carboxylic acid (10.78%) and 9, 12-Octadecadienoic acid (7.38%)] were identified and subjected to computation corrosion study, the binding energy for the constituents of the blend on Fe surface were computed using Accelrys Material Studio and the mean values were found to be −327.097 kJ/mol, −446.943 kJ/mol, −602.826 kJ/mol, −608.625 kJ/mol and −693.749 kJ/mol respectively.

关键词： Arabic gum Cashew gum Synergy DFT Corrosion

Vlendelian randomization： loosening the Gordian knot of testosterone and male ageing

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Asian Journal of Andrology 2013年第5期15卷 579-581页

作者： david J Handelsman ANZAC Research Institute University of SydneySydney NSW 2139 Australia

It is unknown whether the reduced blood testosterone among unselected older men （＂andropause＂） compared to healthy younger men is due to ageing per se or as a non-specific adaptive reaction to chronic diseases acc... 详细信息

关键词： Mendelian randomization loosening male ageing

Attachment ability of combined biomimetic adhesive micro-textures of different shapes

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Friction 2023年第8期11卷 1430-1441页

作者： david BADLER Yuri KLIGERMAN Haytam KASEM Faculty of Mechanical Engineering Technion-Israel Institute of TechnologyHaifa 3200003Israel Department of Mechanical Engineering Azrieli College of EngineeringJerusalem 9103501Israel

There are various potential applications of biomimetic adhesive solutions including climbing robotic systems,mobile sensor platforms,and biomedical applications such as patches for external *** resistance to both normal and tangential loads,however,is a critical issue that still needs to be *** animals have developed exceptional attachment mechanisms based on combined fibrillar elements of different shapes and *** investigation of combined biomimetic adhesive micro-textures on tribological performances such as adhesion,friction,and peeling resistance is needed to apply this idea to the design of an artificial texture having similar“biomimetic”*** the present study,we demonstrate that combinations of different shapes of biomimetic adhesive micro-textures show increased efficiency under different contact environments and enable long-term adhesive *** work sheds light on combinations of different element shapes inspired by nature and their adhesive efficiency as a function of the ratio of each biomimetic element,as well as their spatial repartition.

关键词： biomimetic micro-textures adhesion friction peeling

STOCK LOAN VALUATION UNDER A REGIME-SWITCHING MODEL WITH MEAN-REVERTING AND FINITE MATURITY

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Journal of Systems Science & Complexity 2010年第3期23卷 572-583页

作者： david PRAGER Department of Mathematics University of Georgia

Stock loans are business contracts between borrowers and lenders in which the borroweruses shares of stock as collateral for the *** the value of the collateral is subject to wide andfrequent price swings,valuing such a transaction behaves more like an option pricing problem thana debt valuation *** paper will list,prove,and analyze formulas for stock loan valuationwith finite horizon under various stock models,including classical geometric Brownian motion,meanreverting,and two-state regime-switching with both mean-reverting and geometric Brownian *** examples are reported to illustrate the results.

关键词： Mean reversion regime switching stock loan.