Shear resistance characteristics and influencing factors of root-soil composite on an alpine metal mine dump slope with different recovery periods

Artificial vegetation restoration is the main measure for vegetation restoration and soil and water conservation in alpine mine dumps on the Qinghai-Tibet Plateau,China.However,there are few reports on the dynamic changes and the influencing factors of the soil reinforcement effect of plant species after artificial vegetation restoration under different recovery periods.We selected dump areas of the Delni Copper Mine in Qinghai Province,China to study the relationship between the shear strength and the peak displacement of the root-soil composite on the slope during the recovery period,and the influence of the root traits and soil physical properties on the shear resistance characteristics of the root-soil composite via in situ direct shear tests.The results indicate that the shear strength and peak displacement of the rooted soil initially decreased and then increased with the increase of the recovery period.The shear strength of the rooted soil and the recovery period exhibited a quadratic function relationship.There is no significant function relationship between the peak displacement and the recovery period.Significant positive correlations(P<0.05)exists between the shear strength of the root-soil composite and the root biomass density,root volume density,and root area ratio,and they show significant linear correlations(P<0.05).There are no significant correlations(P>0.05)between the shear strength of the root-soil composite and the root length density,and the root volume ratio of the coarse roots to the fine roots.A significant negative linear correlation(P<0.05)exists between the peak displacement of the rooted soil and the coarse-grain content,but no significant correlations(P>0.05)with the root traits,other soil physical property indices(the moisture content and dry density of the soil),and slope gradient.The coarse-grain content is the main factor controlling the peak displacement of the rooted soil.

Intergeneric Somatic Hybrid Plants Between Citrus and Poncirus trifoliata and Evaluation of Their Root Rot Resistance

Protoplasts of Page tangelo (Citrus reticulata Blanco×C. paradisi Macf.) cell suspension culture were electrically fused with mesophyll protoplasts isolated from trifoliate orange (Poncirus trifoliata (L.) Raf.). More than 150 plantlets regenerated after 4-5 months of culture. The regenerated plants were trifoliate with well developed root systems. Root_tip chromosome counting of more than 20 randomly selected plants revealed that they were all tetraploids (2n=4x=36). RAPD analysis of 7 randomly selected plants verified their hybridity. Inoculation of citrus Phytophthora parasitica Dastar toxin on leaves of somatic hybrids and both parental genotypes showed that Page tangelo was moderately susceptible, and trifoliate orange was highly resistant while the somatic hybrids were resistant. The potential of this somatic hybrid as rootstock is also discussed.

Study on Screening of Fungi with High-resistance against Chromium and on Related Characteristics

[Objective] The aim was to separate chromium-resistant microorganism from soil contaminated by chromium.[Method] Separation and purification technique was used as follows：different concentrations of Cr^6＋ were added into medium,and chromium-resistant fungi were screened after separations and domestications.The selected fungi were under preliminary identification according to its morphological and colony characteristics.Then,related biological characteristics were studied,including measurement of growth curve,growing effects by temperature,pH value and osmotic pressure.[Result] The Cr（VI） with concentration of 1 000 mg/L was separated and selected from soils in ten different places contaminated seriously by heavy metal in adjacent region of Yulin City.Considering its morphological and colony characteristics,it was preliminarily identified as saccharomycetes,which can well grow within 15-37 ℃,and whose most suitable temperature was 28℃.Bacterial strain can grow well with pH of 4-10,and the optimum pH was 7.2;besides,it can grow well with NaCl concentration of 0.5%-5.0%.Through the experiment,the bacteria was found with resistance not only to chromium,but also to heavy metals such as Pb＋Cu,Cu＋Fe,Pb＋Fe,and Pb＋Cu＋Fe.[Conclusion] The fungi selected from the experiment were of good adaptability to natural environment,and it also had resistance to other heavy metals.

Resistance Characteristics of Hydraulic Oil through Isodiametric T-type Duct with Sharp Corners

Rational determination and reduction of local energy loss of oil flow at pipe junctions are of important significance to improve hydraulic pipeline＇s work efficiency, especially for complex hydraulic pipeline connected by isodiametric T-type ducts with sharp comers to get combined and divided flow. From this point of view, the formulae of resistance loss for combined flow and divided flow through isodiametric T-type duct with sharp comers as well as the correlations of resistance loss coefficients in the branches of the duct are derived using energy method. On this basis, resistance characteristics of hydraulic oil in the duct are obtained by numerical simulation of different flow modes, which are commonly applied in hydraulic pipelines, using computational fluid dynamics （CFD） method, and the reasons for the resistance loss are analyzed based on the pressure change mechanism in the flow field. A part of simulation results was validated with the reference data. The research shows that for combined flows the resistance loss of symmetrical is lower than that of unsymmetrical to obtain low speed in common branch, but to gain high speed is quite the contrary, for divided flows, the symmetrical is always a reasonable choice to reduce resistance loss. These conclusions can be applied to optimize the design of hydraulic pipeline.

Dynamic mechanical characteristics and application of constant resistance energy-absorbing supporting material

In deep underground engineering,rock burst and other dynamic disasters are prone to occur due to stress concentration and energy accumulation in surrounding rock.The control of dynamic disasters requires bolts and cables with high strength,high elongation,and high energy-absorbing capacity.Therefore,a constant resistance energy-absorbing(CREA)material is developed.In this study,the dynamic characteristics of the new material are obtained via the drop hammer tests and the Split Hopkinson Pressure Bar(SHPB)tests of the new material and two common bolt(CB)materials widely used in the field.The test results of drop hammer test and SHPB test show that the percentage elongation of CREA material is more than 2.64 and 3.22 times those of the CB material,and the total impact energy acting on CREA material is more than 18.50 and 21.84 times,respectively,indicating that the new material has high elongation and high energy-absorbing capacity.Subsequently,the CREA bolts and cables using the new material are developed,which are applied in roadways with high stress and strong dynamic disturbance.The field monitoring results show that CREA bolts and cables can effectively control the surrounding rock deformation and ensure engineering safety.

Detection of the assimilation characteristics of iron ores: Dynamic resistance measurements

Resistance in iron ore undergoes a sharp change of up to several orders of magnitude when the sintered solid phase changes to liquid phase.In view of the insufficiency of existing assimilation detection methods,a timing-of-assimilation reaction is proposed,which was judged by continuously detecting the changes in resistance at the reaction interface.Effects of pole position and additional amounts of iron ore on assimilation reaction timing were investigated.The results showed that the suitable depth of pole groove was about 2 mm,and there was no obvious impact when the distance of the poles changed from 4 to 6 mm,or the amount of iron ore changed from 0.4 to 0.6 g.The temperature of sudden change of resistance in the temperature-resistant image was considered to be the lowest assimilation temperature of iron ore.The accuracy of this resistance method was clarified by X-ray diffraction,optical microscope,and scanning electron microscope/energy dispersive spectrometer(SEM/EDS)analyses.

Lodging Resistance Related to Root Traits for Mechanized Wet-Seeding of Two Super Rice Cultivars

Mechanical hill wet-seeded rice machine is beneficial for establishing and growing uniform rows of seedlings.However,there is limited knowledge regarding the effects of the establishment of furrows on growth,lodging and yield,and their relationships with root traits.In this study,field experiments were conducted during 2012 and 2013 using two super rice varieties(hybrid rice Peizataifeng and inbred rice Yuxiangyouzhan)under three furrow establishment treatments(T1,both water and seed furrows were established by the machine;T2,only seed furrows were established by the machine;and T3,neither water nor seed furrows were established by the machine).Lodging index,lodging-related traits,grain yield,above-ground dry weight and root traits were measured.The results showed that the lodging index was significantly affected by the treatments with furrows(T1 and T2).The strongest lodging resistance was detected in the mechanical hill wet-seeded rice with furrow treatment(T1)in both 2012 and 2013.Lodging resistance was strongly related to the breaking resistance.No significant difference was found in grain yield or dry weight of the mechanical hill wet-seeded rice.Therefore,the mechanical hill wet-seeded rice with furrow treatment increased rice lodging resistance,which was related to root traits.

Analysis of sliding electric contact characteristics in augmented railgun based on the combination of contact resistance and sliding friction coefficient

The contact resistance between the armature and rails is an important indicator of the contact characteristics in electromagnetic launches.As the contact resistance depends not only on the contact state but also on the contact stress and temperature,there are some limitations in analyzing the contact characteristics using only the contact resistance.In this paper,the contact characteristics of the augmented railgun are analyzed by the combination of contact resistance and sliding friction coefficient.Firstly,the theoretical calculation model of the contact resistance and friction coefficient of the augmented electromagnetic railgun is established.Then the contact resistance and friction coefficient are calculated by the measured values of the muzzle voltage,rail current and armature displacement.Finally,the contact characteristics are analyzed according to the features of the waveforms of the contact resistance and the friction coefficient,and the analysis conclusions are verified by experimental rail images.The results showed that:the aluminum melt film gradually formed on the contact surface reduces the contact resistance and the friction coefficient;the wear and erosion of the armature cause deterioration of the contact state;after the transition,the reliability of the sliding contact between the armature and rails decreases,resulting in an increase in contact resistance.

Increase in root density induced by coronatine improves maize drought resistance in North China

Drought stress caused by insufficient irrigation or precipitation impairs agricultural production worldwide.In this study,a two-year field experiment was conducted to investigate the effect of coronatine(COR),a functional analog of jasmonic acid(JA),on maize drought resistance.The experiment included two water treatments(rainfed and irrigation),four COR concentrations(mock,0μmol L^(-1);A1,0.1μmol L^(-1);A2,1μmol L^(-1);A3,10μmol L^(-1))and two maize genotypes(Fumin 985(FM985),a drought-resistant cultivar and Xianyu 335(XY335),a drought-sensitive cultivar).Spraying 1μmol L^(-1)COR at seedling stage increased surface root density and size,including root dry matter by 12.6%,projected root area by 19.0%,average root density by 51.9%,and thus root bleeding sap by 28.2%under drought conditions.COR application also increased leaf area and SPAD values,a result attributed to improvement of the root system and increases in abscisic acid(ABA),JA,and salicylic acid(SA)contents.The improvement of leaves and roots laid the foundation for increasing plant height and dry matter accumulation.COR application reduced anthesis and silking interval,increasing kernel number per ear.COR treatment at 1μmol L^(-1)increased the yield of XY335 and FM985 by 7.9%and 11.0%,respectively.Correlation and path analysis showed that grain yields were correlated with root dry weight and projected root area,increasing maize drought resistance mainly via leaf area index and dry matter accumulation.Overall,COR increased maize drought resistance mainly by increasing root dry weight and root area,with 1μmol L-^(-1)COR as an optimal concentration.

Effects of paclobutrazol application on plant architecture,lodging resistance,photosynthetic characteristics,and peanut yield at different single-seed precise sowing densities

The key to high-yielding peanut cultivation is the optimization of agricultural production practices.Regulating single-seed precise sowing(SSPS)density and paclobutrazol(Pbz)application concentration are effective practices that increase peanut yield by improving plant architecture,lodging resistance,and photosynthetic characteristics.Therefore,we conducted a two-factor field optimization experiment for the sowing density(D1:1.95×10^(5)plants ha^(-1),D52:2.40×10plants ha^(-1),D3:2.85×10^(5)plants ha^(-1),and D4:3.30×10^(5)plants ha^(-1))and Pbzapplication concentration(P0:0 mg L^(-1)and P1:100 mg L^(-1)).The objective was to optimize agricultural production practices and provide a theoretical basis for highyielding peanut cultivation by evaluating the effects of sowing density and Pbzapplication on plant architecture,lodging resistance,photosynthetic characteristics,and yield.The results showed that at the same Pbzapplication concentration,increasing sowing density increased lodging percentage and reduced leaf photosynthetic capacity.At the same sowing density,Pbzapplication reduced lodging percentage by decreasing plant height(PH),improving lignin biosynthesis-related enzyme activities,and enhancing stem puncture strength(SPS)and breaking strength(SBS).The paclobutrazol-induced alterations in plant architecture and lodging resistance improved light transmission at the middle and bottom leaf strata,resulting in the increase in relative chlorophyll content and net photosynthetic rate(Pn)of leaves.Furthermore,D3P1treatment had the highest peanut yield among all treatments.In summary,the production strategy combining the sowing density of 2.85×10^(5)plants ha^(-1)with the application of100 mg L^(-1)Pbzwas found to be the optimal agricultural production practice for giving full play to production potential and achieving higher peanut yield.

Sub-synchronous frequency domain-equivalent modeling for wind farms based on rotor equivalent resistance characteristics

The equivalent simplification of large wind farms is essential for evaluating the safety of power systems.However,sub-synchronous oscillations can significantly affect the stability of power systems.Although detailed mathematical models of wind farms can help accurately analyze the oscillation mechanism,the solution process is complicated and may lead to problems such as the“dimensional disaster.”Therefore,this paper proposes a sub-synchronous frequency domain-equivalent modeling method for wind farms based on the nature of the equivalent resistance of the rotor,in order to analyze sub-synchronous oscillations accurately.To this end,Matlab/Simulink is used to simulate a detailed model,a single-unit model,and an equivalent model,considering a wind farm as an example.A simulation analysis is then performed under the sub-synchronous frequency to prove that the model is effective and that the wind farm equivalence model method is valid.

Resistance Evaluation of Soybean Germplasm from Huanghuai Region to Phytophthora Root Rot

The aim of the study was to establish a set of differential strains and to identify soybean resistant genes to Phytophthora root rot and then to apply those strains for analysis of the resistant genes Rps1a,Rps1c,and Rps1k that soybean cultivars or lines may carry.Virulence formula of 125 Phytophthora sojae isolates were determined using the hypocotyls inoculation technique,the strains,which includ 6 isolates with different virulence formulas,were applied to identify the resistance of 55 soybean cultivars or lines and resistant genes were analyzed using the gene postulating procedure.Eighteen reaction types occurred in 55 cultivars or lines and results of gene postulation indicated that 2 cultivars or lines probably carried gene Rps1c and no cultivar may carry genes Rps1a or Rps1k.A few of soybean cultivars or lines from Huanghuai Region carry Rps genes Rps1a,Rps1c and Rps1k and tend to infect by P.sojae,so resistant cultivars or lines need to be bred and popularized actively.

A Phenotyping Protocol for Detailed Evaluation of Apple Root Resistance Responses Utilizing Tissue Culture Micropropagated Apple Plants

In the post-genomics era, reliable phenotypes are considered the bottleneck for unraveling the genetic control over the biology of interest. Phenotyping resistance response of roots to infection by soilborne pathogen is more challenging compared to that of plant aerial parts. In additional to the hidden nature and small stature of fine roots where infection occurs, extra obstacles exist for rosaceae tree crops such as apple. Due to self-incompatible reproduction and high-level heterozygosity of apple genome, genetically identical apple plants cannot be produced through apple seed germination. Here we report an established phenotyping protocol which includes a streamlined tissue culture procedure for micropropagation of uniform apple plants, standardized inoculation procedure using Pythium ultimum, and multilayered evaluating methods on apple root resistance traits. Because of the implementation of tissue culture based micropropagation procedure, constant availability of the uniform plants with defined genetic background, equivalent age and non-contaminated roots overcame a longstanding barrier of systematic and detailed phenotypic characterization of apple root resistance traits. Repeated infection assays by root-dipping inoculation demonstrated the reproducible and wide-range plant survival rates, from single-digit to over 90% survived plants for a given genotype. Genotype-specific values due to P. ultimum inoculation on shoot and root biomass reduction, maximum root lengths, leaf number and cumulative leaf areas were quantified between mock-inoculated and P. ultimum infected plants. Use of a glass-box container offered enhanced accessibility and minimized invasiveness for continuous and non-disruptive observation on the necrosis progression patterns along inoculated roots. With the assistance of a dissecting microscope, the genotype-specific resistance responses along the infected apple roots were captured and analyzed in detail. This reported phenotyping protocol represents a major development and should be easily adopted for other rosacea tree fruit crops with minor modifications.

Characteristics of Resistance Triggering of a Pulsed Vacuum Arc Ion Source

Triggering scheme is a significant factor that may influence the process of vacuum arc initiation. In this work, the characteristics of resistance triggering of a pulsed vacuum arc ion source are investigated and compared with the independent pulse generator triggering. The results show that although the resistance triggering method is capable of triggering a vacuum arc ion source by properly choosing the resistance and electric parameters, it inevitably increases the rise time of the arc current. A high speed multiframe camera is used to reveal the transition process o~ arc initiation during one shot. From the images it is conjectured that the lower voltage between the cathode and the anode may be the reason that leads to the lower transition speed of discharge at the moment of arc initiation.

Polygenic Heritability of Rose Root Rot Disease Resistance in Offspring of Rosa multiflora

Rose root rot disease caused by Pythium helicoides Drechsler has brought heavy damage to cut rose production in Japan,and it has became apparent that Rosa multiflora showed resistance to this disease.Roses have been bred by interspecies crossing with Rosa species including of R.multiflora,and many progenies of R.multiflora have been bred as determined cluster-flowered roses.However,the genetic architecture of this resistance remains.So,in this study,four kinds of R.multiflora and 21 rose cultivars that have been clarified in the cross-fertilization genealogy with R.multiflora were used as plant materials,and the inheritability of resistance to root rot disease was investigated.Four kinds of R.multiflora had all high resistance,and the resistance to root rot disease in R.multiflora was inherent characteristic of species.Five varieties not less than 50% in relatedness with R.multiflora were shown as varied ‘resistant’ and ‘moderately resistant’.Therefore,the inherent resistant characteristic in R.multiflora was not controlled by single major gene,and the resistibility in R.multiflora was not cytoplasmic but nuclear heredity.Although there was significant negative relation between relative root rot severity and relatedness with R.multiflora,the variance of relative root rot severity had tendency to expand as relatedness with R.multiflora reduced.This result,therefore,indicated that the contingency of resistance expression increased as the relatedness with R.multiflora was reduced.The varieties having low degree of relatedness with R.multiflora had similar relative root rot severity with R.multiflora.These results indicated that we would be able to select resistant roses from progenies crossed with R.multiflora.

Modeling of resistance characteristics of a continuously-graded distributed Bragg reflector in a 980-nm vertical-cavity surface-emitting laser

The resistance characteristics of a continuously-graded distributed Bragg reflector（DBR） in a 980-nm verticalcavity surface-emitting laser（VCSEL） are modeled in detail.The junction resistances between the layers of both the p-and n-DBR mirrors are analysed by combining the thermionic emission model and the finite difference method.In the meantime,the intrinsic resistance of the DBR material system is calculated to make a comparison with the junction resistance.The minimal values of series resistances of the graded p-and n-type DBR mirrors and the lateral temperature-dependent resistance variation are calculated and discussed.The result indicates the potential to optimize the design of the DBR reflectors of the 980-nm VCSELs.

Mitigative Effect of <i>Bacillus subtilis</i>QM3 on Root Morphology and Resistance Enzyme Activity of Wheat Root under Lead Stress

Lead (Pb) is an environmental pollutant extremely toxic to plants and other living organisms including humans. In order to research the relieve effect of Bacillus subtilis QM3 on wheat roots (Triticum aestivum L.), after wheat seeds germination for two days, wheat root caused, the experimental materials were divided into four large groups and each large group was placed in 6 petri dishes as six small groups, and then four large groups respectively cultivated with sterile water (CK), 108 CFU/ml B. subtilis QM3 (B1), 107 CFU/ml B. subtilis QM3 (B2) and 106 CFU/ml B. subtilis QM3 (B3) for 2 days, after that stressed with lead nitrate, Pb (NO)2, Pb2+ concentration calculation at five concentrations (50, 250, 500, 1000, 2000 mg/L), sterile water and different Pb2+ concentration liquid respectively cultivated the 6 small groups in each large group measuring root morpholog and assaying changes of antioxidant enzyme activity. The results showed that: with the increase of the Pb2+ concentration, root morphology index and the activity of antioxidant enzyme increased first and then decreased. Root morphology index reached the maximum in 50 mg/L Pb2+ concentration. B. subtilis QM3 clearly promoted the growth of the root and the antioxidant enzyme activity (p 0.05). Without Pb stress, B. subtilis QM3 had the best improving effect on root morphology. When Pb2+ concentration was 50 mg/L, superoxide dismutase (SOD) and ascorbate peroxidase (APX) reached the maximum. SOD activity, compared with CK, B1, B2 and B3 respectively, increased by 8.05%, 27.41% and 9.79%. APX activity, compared with CK, B1, B2 and B3 respectively, increased by 52.70%, 111.15% and 14.16%. Catalase (CAT) and peroxidase (POD) reached the maximum at the Pb2+ concentration was 500 mg/L. CAT activity, compared with CK, B1, B2 and B3 respectively, increased by 59.93%, 83.46% and 70.59%. POD activity, compared with CK, B1, B2 and B3 respectively, increased by 2.88%, 10.11% and 7.67%. Result suggested that B. subtilis QM3 could improve root growth and antioxidant enzyme activity of the wheat root under lead stress.

Identification of quantitative trait loci and epistasis for root characteristics and root exudations in maize (Zea mays L.) under deficient phosphorus

The phosphorus uptake （PU） in above-ground parts of plant, root characteristics and root exudations as well as the quantitative trait loci （QTLs） associated with these characteristics were determined for a F2：3 population derived from the cross of two contrasting maize （Zea mays L.） genotypes, 082 and Yel07. A total of 241 F2：3 families were evaluated in replicated trials under deficient phosphorus conditions in 2007 at two sites （Kaixian County and Southwest University, Chongqing, P. R. China）. The results show pleiotropy and close linkage among QTLs. Four common regions in different environments were in bnlg100- bnlg1268b （bins 1.02） for QTL of H＋, bnlg1268a-umc1290a （bins 1.09） for QTL of AP （acid phospbatase activity）, dupssrl5- P 1MT/a （bins 6.06） for QTLs of PU （phosphorus uptake） and RW （root weight）, and P IM3/d-P1M3/g （bins9.04） for QTLs of PU and AP. These QTLs are non-environment or minor QTLs x environment. By epistatic analysis, three main QTLs and eighteen QTLs x QTLs interactions were detected for the seven measured characteristics. These QTLs may affect trait expression by epistatic interaction with the other loci, and make a substantial contribution to phosphorus utilization efficiency, which should be considered when breeding maize varieties with high P efficiency. Two regions were detected in dupssrl 5- P1MT/a （bins 6.06） for QTL of RW and P1M3/d- P 1M3/g （bins 9.04） for QTL of PU and AP. They were detected in two different environments and by two methods of QTL analysis, which were useful for marker-assisted selection.

Experimental investigation on debris flow resistance and entrainment characteristics:effects of the erodible bed with discontinuous grading

Debris flow deposits in natural channels typically have a wide grain size distribution(GSD).The effects of bed sediment GSD on the basal entrainment rate are neglected in current debris flow erosion models.Field investigations have detected three different vertical graded bedding structures:normal,inverse,and mixed-gradation,characterized by discontinuous gradation sediment and almost without intermediate-sized particles.This study conducted small-scale flume experiments to investigate the debris flow resistance forces and entrainment characteristics by incorporating the effects of discontinuous grading bed sediments.Discontinuous graded bed sediments with varying fine particle content,volumetric water content(VWC),and roundness were designed for comparison.Debris flow resistance in erodible beds generally increased in the group with gravel of larger-sized coarse particle,lower roundness,and higher bed sediment VWC.For discontinuous grading bed sediment,the entrained depths increased in the group with gravel of smaller coarse particle sizes,larger amounts of fine particles,and higher sediment roundness,and decreased with larger VWCs.This abnormality may be attributed to the disproportionately large effects of viscous flow resistance in our small-scale flume tests.The maximum erosion rates of the continuous bed sediment were higher than those of the corresponding discontinuous bed sediment with the same maximum coarse gravel size.This is because,for discontinuous grading bed sediments,localized failure of intermediate-sized sediment grains may cause a large-scale collapse of the solid grain skeleton and enhance basal entrainment rates.A revised formula for calculating the debris flow entrainment rate is proposed by incorporating the kurtosis coefficient,which describes the distribution of discontinuous bed sediments and fine particle content.Our revised formula could facilitate an elaborate estimation of basin erosion and sediment runoff and reveal the development and recession of debris flow fans.

Flow resistance characteristics of water in narrow annulus during heat exchange

Considering the special resistance characteristics of fluids flowing through ducts with small gaps, experiments are performed to investigate the resistance characteristics of single-phase water, which is forced to flow through ver tical annuli. The gap sizes are 0.9, 1.4 and 2.4mm, respectively. The experiments are conducted under condition of 1atm. The water in the annuli is heated by high temperature water reversely flowing through the inner tube and the outer annulus. The results show that the flow pattern begin to change from laminar to turbulent before Reynolds number approaches 2000, the flow resistance in annulus has little relations with the temperature difference and ways of being heated, but mainly depends on the ratio of mass flux to the width of annulus.