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molecular identification and population dynamics of two species of Pemphigus （Homoptera： Pemphidae） on cabbage

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Insect Science 2009年第2期16卷 115-124页

作者： Naiqi Chen Tong-Xian Liu mamoudou Setamou J. Victor French Eliezer S. Louzada Department of Entomology Texas AgriLife Research Texas A&M University System Weslaco Citrus Center Texas A&M University- Kingsville Citrus Center Weslaco TX 78596 USA

The poplar petiole gall aphid, Pemphiguspopulitransversus Riley, has been one of the major pests on cruciferous vegetable in the Rio Grande Valley （LRGV） of texas since the late 1940s. It normally migrates from poplar trees to cruciferous vegetables in the fall, and migrates back to the trees in early spring of the coming year. Some root-feeding aphids were found on cruciferous vegetables in late spring and early summer in 1998 and the following years. Those aphids have been identified as Pemphigus obesinymphae moran. This discovery completely changed the current knowledge about the root-feeding aphids on cruciferous vegetables in the LRGV. Due to their small size, morphological and feeding similarities between P. populitransversus and P. obesinymphae, their identification and distinction are difficult. In this study, random amplification of polymorphic DNA （RAPD） and amplified fragment length polymorphism （AFLP） were used to distinguish these two species over a period of time when the two species occurred together, or separately, in cabbage fields. The two species occurred on cabbage at different times of the year, and overlapped from October to June. From may to October, both species migrated to their primary hosts. The apterous aphids found on cabbage in winter contained mainly P. obesinymphae, whereas in early spring more apterous P. populitransversus were recovered. The root-feeding aphids would feed on cabbage plants as long as this host was available even during the hot, dry summer in the LRGV, although their populations were generally low. Both RAPD and AFLP techniques were efficient in discriminating the two species that showed obviously genetic variability. These molecular techniques confirmed the existence of the two aphid species in apterous samples collected from the soil in cabbage fields in the LRGV, and the results performed by RAPD were confirmed by AFLP. Furthermore, the results suggest that RAPD technique was a better choice despite its reproducib

关键词： AFLP cabbage identification RAPD root aphid

Crystalline phase of Y_2O_3 :Eu particles generated in a substrate-free flame process

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Particuology 2011年第1期9卷 24-31页

作者： Bing Guoa Hoon Yim Wonjoong Hwang matt Nowell Zhiping Luo Department of mechanical Engineering Texas A&M University College Station TX 77843 USA EDAX-TSL EDAX Inc. Draper UT84020 USA microscopy and Imaging Center Texas A&M University College Station TX 77843 USA

In this study, factors affecting the crystal structure of flame-synthesized Y2O3 ：Eu particles were investigated, especially the particle size effect and its interaction with Eu doping concentration, Polydisperse Y2O3：Eu （size range 200 nm to 3μm） powder samples with Eu doping concentrations from 2,5 mol% to 25 mol% were generated in either H2/air or H2/O2 substrate-free flames. The crystal structure of the powder samples was determined by powder X-ray diffraction （XRD）, which was complemented by pho- toluminescence （PL） measurements. Single particle crystal structure was determined by single particle selected area electron diffraction （SAED）, and for the first time, by electron backscatter diffraction （EBSD）. H2/air flames resulted in cubic phase Y2O3：Eu particles with hollow morphology and irregular shapes, Particles from H2/O2 flames had dense and spherical morphology; samples with lower Eu doping concen- trations had mixed cubic/monoclinic phases; samples with the highest Eu doping concentrations were phase-pure monoclinic. For samples generated from H2/02 flames, a particle size effect and its interaction with Eu doping concentration were found： particles smaller than a critical diameter had the monoclinic phase, and this critical diameter increased with increasing Eu doping concentration, These findings suggest that the formation of monoclinic Y2O3：Eu is inevitable when extremely hot substrate-free flames are used, because typical flame-synthesized Y203 ：Eu particle sizes are well below the critical diameter, However, it may be possible to generate particles with dense, spherical morphology and the desired cubic structure by using a moderately high flame temperature that enables fast sintering without melting the particles.

关键词： Flame synthesis Aerosol Size effect Crystal structure Y2O3:Eu Particles

Synergistic effects of zeolitic imidazolate frameworks(ZIFs)with different transition metals on intumescent flame-retarded polypropylene composites:A comparative study

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Journal of materials Science & Technology 2023年第24期155卷 102-110页

作者： Yufeng Quan Ruiqing Shen Christian Schweizer Pradeep Parajuli Zhuoran Zhang Waruna Kulatilaka Qingsheng Wang Artie mcFerrin Department of Chemical Engineering Texas A&M University College Station TX 77843-3122 USA J. mike Walker ’66 Department of mechanical Engineering Texas A&M University College Station TX 77843-3123 USA

The use of intumescent flame retardants(IFRs)is considered an environmentally friendly and cost-effective strategy to suppress potential fire hazards from synthetic ***,some conventional IFRs are neither efficient in developing a thermally stable char layer nor reducing the release of toxic byproducts during polymer *** this work,we aim to discuss the effects of zeolitic imidazolate frameworks(ZIFs)on synergistically improving the flame retardancy behaviors in polypropylene(PP)composites,including thermal degradation(evolved gas analysis),free radical reactions in the gaseous phase(in-situ chemiluminescent image analysis),and carbonaceous structure in the condensed phase(micro-morphology and composition analysis).It is found that the transition metals in ZIFs can catalytically accelerate the crosslinking reaction at a lower initial temperature and decrease the amount of hydrocarbon volatiles in the gaseous *** ignited,the embedded ZIFs can firstly bridge adjacent phosphorus chains in the polymer matrix to expand crosslinking degrees and then they are anchored in the developed N-doped phospho-carbonaceous networks after *** a result,more compact char residue structures are observed in the condensed phase for ZIF-reinforced *** example,by replacing 2 wt%of IFR with ZIF-67,the peak heat release rate,peak smoke production rate,and peak CO production rate are reduced by 69%,80%,and 72%,respectively,when compared to the conventional *** results indicate an excellent solution to resolve inherent fire hazards associated with IFRs in polymers and achieve necessary efficiency for industrial *** also provides a new strategy for determining flammability characteristics and combustion mechanisms of polymer composites using in-situ chemiluminescence analysis.

关键词： Polymer flammability Intumescent flame retardants Zeolitic imidazolate frameworks Thermal degradation Free radical analysis Flame retardant mechanism

Hermitian geometry on the resolvent set(Ⅱ)

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Science China mathematics 2021年第2期64卷 385-398页

作者： Ronald G.Douglas Rongwei Yang Department of mathematics Texas A&M UniversityCollege StationTX 77843USA School of mathematical Sciences Tianjin Normal UniversityTianjin 300387China Department of mathematics and Statistics State University of New York at AlbanyAlbanyNY 12222USA

For an element A in a unital C^(*)-algebra B,the operator-valued 1-formωA(z)=(z-A)^(-1) dz is analytic on the resolvent setρ(A),which plays an important role in the functional calculus of *** paper defines a class of Hermitian metrics onρ(A)through the coupling of the operator-valued(1,1)-formΩA=-ωA^(*)∧ωA with tracial and vector *** main goal is to study the connection between A and the properties of the metric concerning curvature,arc length,completeness and singularity.A particular example is when A is quasi-nilpotent,in which case the metric lives on the punctured complex plane C\{0}.The notion of the power set is defined to gauge the"blow-up"rate of the metric at 0,and examples are given to indicate a likely link with A’s hyper-invariant subspaces.

关键词： C^(*)-algebra Hermitian metric curvature arc length Fuglede-Kadison determinant quasi-nilpotent operator power set

The influence of bacteria on multitrophic interactions among plants, psyllids, and pathogen

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Insect Science 2017年第6期24卷 961-974页

作者： Cecilia Tamborindeguy Ordom Brian Huot Freddy Ibanez Julien Levy Department of Entomology Texas A&M University College Station Texas USA Department of Horticultural Sciences Texas A&M University College Station Texas USA

The recent emergence ofseveralplant diseases caused by psyllid-borne bacterial pathogens worldwide （Candidatus Liberibaeter spp.） has created renewed interest on the interaction between psyllids and bacteria. In spite of these efforts to understand psyllid association with bacteria, many aspects of their interactions remain poorly understood. As more organisms are studied, subtleties on the molecular interactions as well as on the effects of the bacteria on the psyllid host are being uncovered. Additionally, psyllid-borne bacterial phytopathogens can also affect the host plant, which in turn can impact psyllid physiology and behavior. Here, we review the current literature on different aspects of the influence of bacteria on multitrophic interactions among plants, psyllids, and pathogens. We then highlight gaps that need to be addressed to advance this field, which can have significant implications for controlling these newly emergent and other plant diseases.

关键词： bacteria interaction Liberibacter microbiome phytoplasma psyllid

An analysis of first-time and repeat visitors to Korean national parks from 2007 and 2013

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Journal of mountain Science 2017年第12期14卷 2527-2539页

作者： yunseon choe michael a.schuett kyu-won sim department of tourism management college of hotel and tourism managementkyung hee university26Kyungheedae-roDongdaemun-guSeoul02447Republic of Korea department of recreation park and tourism sciencestexas a&m university600 John Kimbrough BirdCollege StationTex as 77843USA national park research institute korea national park serviceWonju 26441Republic of Korea

This paper examined visitors to Bukhansan National Park in Korea based on first-time and repeat visitation. Bukhansan National Park is Korea's most heavily visited national park with annual visitation of six million visitors in 2015. Data used in this article were collected on-site in the park in 2007 and 2013 by the Korea National Park Service(KNPS).The study variables included socio-demographics,travel behavior, motivation, and satisfaction with park attributes, services and facilities. Data were analyzed by each study year for first-time and repeat *** showed significant differences for both firsttime and repeat visitors on several socio-demographic,travel behavior, and motivation variables within each study year. For satisfaction with park attributes,facilities and services, first-time visitors were significantly different from repeat visitors on seven variables for both years. Implications are given regarding programs and services to improve visitor satisfaction and sustain the natural, cultural and historical resources at Bukhansan National Park and other national parks in Korea. Future research suggestions are provided to learn more about visitor characteristics, standards of quality and preferences in the national parks.

关键词： Bukhansan National Park Korean national parks Visitor behaviour market segmentation Visitor satisfaction

Nearshore regional behavior of lightning interaction with wind turbines

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Journal of Ocean Engineering and Science 2016年第1期1卷 66-76页

作者： Gilbert A.malinga John m.Niedzwecki Zachary Department of Civil Engineering Texas A&M UniversityCollege StationTXUSA

The severity of lightning strikes on offshore wind turbines built along coastal and nearshore regions can pose safety concerns that are often *** this research study the behavior of electrical discharges for wind turbines that might be located in the nearshore regions along the East Coast of China and Sea of Japan were characterized using a physics-based model that accounted for a total of eleven different geometrical and lightning *** the electrical potential field predicted using this model it was then possible to estimate the frequency of lightning strikes and the distribution of electrical loads utilizing established semi-empirical relationships and available *** total number of annual lightning strikes on an offshore wind turbine was found to vary with hub elevation,extent of cloud cover,season and geographical *** annual lightning strike rate on a wind turbine along the nearshore region on the Sea of Japan during the winter season was shown to be moderately larger compared to the lightning strike frequency on a turbine structure on the East Coast of *** duration electrical discharges,represented using marginal probability functions,were found to vary with season and geographical location,exhibiting trends consistent with the distribution of the electrical peak *** was demonstrated that electrical discharges of moderately long duration typically occur in the winter months on the East Coast of China and the summer season along the Sea of *** contrast,severe electrical discharges are typical of summer thunderstorms on the East Coast of China and winter frontal storm systems along the West Coast of *** electrical charge and specific energy dissipated during lightning discharges on an offshore wind turbine was found to vary stochastically,with severe electrical discharges corresponding to large electrical currents of long duration.

关键词： Nearshore wind turbines Physics based model Lightning strikes Electrical current Strike frequency Electrical charge.

Nonlinear wave dispersion in monoatomic chains with lumped and distributed masses:discrete and continuum models

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Applied mathematics and mechanics(English Edition) 2024年第4期45卷 633-648页

作者： E.GHAVANLOO S.EL-BORGI School of mechanical Engineering Shiraz UniversityShiraz 71963-16548Iran mechanical Engineering Program Texas A&M University at QatarDoha 23874Qatar

The main objective of this paper is to investigate the influence of inertia of nonlinear springs on the dispersion behavior of discrete monoatomic chains with lumped and distributed *** developed model can represent the wave propagation problem in a non-homogeneous material consisting of heavy inclusions embedded in a *** inclusions are idealized by lumped masses,and the matrix between adjacent inclusions is modeled by a nonlinear spring with distributed ***,the model is capable of depicting the wave propagation in bi-material bars,wherein the first material is represented by a rigid particle and the second one is represented by a nonlinear spring with distributed *** discrete model of the nonlinear monoatomic chain with lumped and distributed masses is first considered,and a closed-form expression of the dispersion relation is obtained by the second-order Lindstedt-Poincare method(LPm).Next,a continuum model for the nonlinear monoatomic chain is derived directly from its discrete lattice model by a suitable continualization *** subsequent use of the second-order method of multiple scales(mmS)facilitates the derivation of the corresponding nonlinear dispersion relation in a closed *** novelties of the present study consist of(i)considering the inertia of nonlinear springs on the dispersion behavior of the discrete mass-spring chains;(ii)developing the second-order LPm for the wave propagation in the discrete chains;and(iii)deriving a continuum model for the nonlinear monoatomic chains with lumped and distributed ***,a parametric study is conducted to examine the effects of the design parameters and the distributed spring mass on the nonlinear dispersion relations and phase velocities obtained from both the discrete and continuum *** parameters include the ratio of the spring mass to the lumped mass,the nonlinear stiffness coefficient of the spring,and the wave amplitude.

关键词： nonlinear mass-spring chain discrete model continuum model LindstedtPoincare method(LPm) method of multiple scales(mmS) dispersion phase velocity

Rapid accessibility evaluation for ballistic lunar capture via manifolds: A Gaussian process regression application

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Astrodynamics 2022年第4期6卷 375-397页

作者： Sandeep K.Singh John L.Junkins manoranjan majji Ehsan Taheri Department of Aerospace Engineering Texas A&M UniversityCollege StationTX 77843USA Department of Aerospace Engineering Auburn UniversityAuburnAL 36849USA

In this study,a supervised machine learning approach called Gaussian process regression(GPR)was applied to approximate optimal bi-impulse rendezvous maneuvers in the cis-lunar *** demonstrate the use of the GPR approximation of the optimal bi-impulse transfer to patch points associated with various invariant manifolds in the cis-lunar *** proposed method advances preliminary mission design operations by avoiding the computational costs associated with repeated solutions of the optimal bi-impulsive Lambert transfer because the learned map is computationally *** approach promises to be useful for aiding in preliminary mission *** use of invariant manifolds as part of the transfer trajectory design offers unique features for reducing propellant consumption while facilitating the solution of trajectory optimization *** ballistic capture coasts are also very attractive for mission guidance,navigation,and control robustness.A multi-input single-output GPR model is presented to represent the fuel costs(in terms of theΔV magnitude)associated with the class of orbital transfers of interest *** developed model is also proven to provide efficient *** multi-resolution use of local GPRs over smaller sub-domains and their use for constructing a global GPR model are also *** of the unique features of GPRs is that they provide an estimate of the quality of approximations in the form of covariance,which is proven to provide statistical consistency with the optimal trajectories generated through the approximation *** numerical results demonstrate our basis for optimism for the utility of the proposed method.

关键词： Gaussian process regression supervised learning invariant manifolds ballistic transfers Bayesian inference