Analysis and optimization of stress wave propagation in two-dimensional granular crystals with defects

Granular crystals are compact periodic assemblies of elastic particles in Hertzian contact whose dynamic response can be tuned from strongly nonlinear to linear by the addition of a static precompression force. This unique feature allows for a wide range of studies that include the investigation of new fundamental nonlinear phenomena in discrete systems such as solitary waves, shock waves, discrete breathers and other defect modes. In the absence of precompression, a particularly interesting property of these systems is their ability to support the formation and propagation of spatially localized soliton-like waves with highly tunable properties. The wealth of parameters one can modify (particle size, geometry and material properties, periodicity of the crystal, presence of a static force, type of excitation, etc.) makes them ideal candidates for the design of new materials for practical applications. This thesis describes several ways to optimally control and tailor the propagation of stress waves in granular crystals through the use of heterogeneities (interstitial defect particles and material heterogeneities) in otherwise perfectly ordered systems. We focus on uncompressed two-dimensional granular crystals with interstitial spherical intruders and composite hexagonal packings and study their dynamic response using a combination of experimental, numerical and analytical techniques. We first investigate the interaction of defect particles with a solitary wave and utilize this fundamental knowledge in the optimal design of novel composite wave guides, shock or vibration absorbers obtained using gradient-based optimization methods.

Controlling wave propagation through nonlinear engineered granular systems

We study the fundamental dynamic behavior of a special class of ordered granular systems in order to design new, structured materials with unique physical properties. The dynamic properties of granular systems are dictated by the nonlinear, Hertzian, potential in compression and zero tensile strength resulting from the discrete material structure. Engineering the underlying particle arrangement of granular systems allows for unique dynamic properties, not observed in natural, disordered granular media. While extensive studies on 1D granular crystals have suggested their usefulness for a variety of engineering applications, considerably less attention has been given to higher-dimensional systems. The extension of these studies in higher dimensions could enable the discovery of richer physical phenomena not possible in 1D, such as spatial redirection and anisotropic energy trapping. We present experiments, numerical simulation (based on a discrete particle model), and in some cases theoretical predictions for several engineered granular systems, studying the effects of particle arrangement on the highly nonlinear transient wave propagation to develop means for controlling the wave propagation pathways. The first component of this thesis studies the stress wave propagation resulting from a localized impulsive loading for three different 2D particle lattice structures: square, centered square, and hexagonal granular crystals. By varying the lattice structure, we observe a wide range of properties for the propagating stress waves: quasi-1D solitary wave propagation, fully 2D wave propagation with tunable wave front shapes, and 2D pulsed wave propagation. Additionally the effects of weak disorder, inevitably present in real granular systems, are investigated. The second half of this thesis studies the solitary wave propagation through 2D and 3D ordered networks of granular chains, reducing the effective density compared to granular crystals by selectively placing wave guiding chains to control the acoustic wave transmission. The rapid wave front amplitude decay exhibited by these granular networks makes them highly attractive for impact mitigation applications. The agreement between experiments, numerical simulations, and applicable theoretical predictions validates the wave guiding capabilities of these engineered granular crystals and networks and opens a wide range of possibilities for the realization of increasingly complex granular material design.

Dynamic characterization of micro-particle systems

Ordered granular systems have been a subject of active research for decades. Due to their rich dynamic response and nonlinearity, ordered granular systems have been suggested for several applications, such as solitary wave focusing, acoustic signals manipulation, and vibration absorption. Most of the fundamental research performed on ordered granular systems has focused on macro-scale examples. However, most engineering applications require these systems to operate at much smaller scales. Very little is known about the response of micro-scale granular systems, primarily because of the difficulties in realizing reliable and quantitative experiments, which originate from the discrete nature of granular materials and their highly nonlinear inter-particle contact forces.

In this work, we investigate the physics of ordered micro-granular systems by designing an innovative experimental platform that allows us to assemble, excite, and characterize ordered micro-granular systems. This new experimental platform employs a laser system to deliver impulses with controlled momentum and incorporates non-contact measurement apparatuses to detect the particles’ displacement and velocity. We demonstrated the capability of the laser system to excite systems of dry (stainless steel particles of radius 150 micrometers) and wet (silica particles of radius 3.69 micrometers, immersed in fluid) micro-particles, after which we analyzed the stress propagation through these systems.

We derived the equations of motion governing the dynamic response of dry and wet particles on a substrate, which we then validated in experiments. We then measured the losses in these systems and characterized the collision and friction between two micro-particles. We studied wave propagation in one-dimensional dry chains of micro-particles as well as in two-dimensional colloidal systems immersed in fluid. We investigated the influence of defects to wave propagation in the one-dimensional systems. Finally, we characterized the wave-attenuation and its relation to the viscosity of the surrounding fluid and performed computer simulations to establish a model that captures the observed response.

The findings of the study offer the first systematic experimental and numerical analysis of wave propagation through ordered systems of micro-particles. The experimental system designed in this work provides the necessary tools for further fundamental studies of wave propagation in both granular and colloidal systems.

Wave uplift pressures on horizontal platforms

The major objective of the study has been to investigate in detail the rapidly-varying peak uplift pressure and the slowly-varying positive and negative uplift pressures that are known to be exerted by waves against the underside of a horizontal pier or platform located above the still water level, but not higher than the crests of the incident waves.

In a "two-dimensional" laboratory study conducted in a 100-ft long by 15-in.-wide by 2-ft-deep wave tank with a horizontal smooth bottom, individually generated solitary waves struck a rigid, fixed, horizontal platform extending the width of the tank. Pressure transducers were mounted flush with the smooth soffit, or underside, of the platform. The location of the transducers could be varied.

The problem of a d equate dynamic and spatial response of the transducers was investigated in detail. It was found that unless the radius of the sensitive area of a pressure transducer is smaller than about one-third of the characteristic width of the pressure distribution, the peak pressure and the rise-time will not be recorded accurately. A procedure was devised to correct peak pressures and rise-times for this transducer defect.

The hydrodynamics of the flow beneath the platform are described qualitatively by a si1nple analysis, which relates peak pressure and positive slowly-varying pressure to the celerity of the wave front propagating beneath the platform, and relates negative slowly-varying pressure to the process by which fluid recedes from the platform after the wave has passed. As the wave front propagates beneath the platform, its celerity increases to a maximum, then decreases. The peak pressure similarly increases with distance from the seaward edge of the platform, then decreases.

Measured peak pressure head, always found to be less than five times the incident wave height above still water level, is an order of magnitude less than reported shock pressures due to waves breaking against vertical walls; the product of peak pressure and rise-time, considered as peak impulse, is of the order of 20% of reported shock impulse due to waves breaking against vertical walls. The maximum measured slowly-varying uplift pressure head is approximately equal to the incident wave height less the soffit clearance above still water level. The normalized magnitude and duration of negative pressure appears to depend principally on the ratio of soffit clearance to still water depth and on the ratio of platform length to still water depth.

The ionic basis of frequency selectivity in hair cells of the bullfrog's sacculus

Hair cells from the bull frog's sacculus, a vestibular organ responding to substrate-borne vibration, possess electrically resonant membrane properties which maximize the sensitivity of each cell to a particular frequency of mechanical input. The electrical resonance of these cells and its underlying ionic basis were studied by applying gigohm-seal recording techniques to solitary hair cells enzymatically dissociated from the sacculus. The contribution of electrical resonance to frequency selectivity was assessed from microelectrode recordings from hair cells in an excised preparation of the sacculus.

Electrical resonance in the hair cell is demonstrated by damped membrane-potential oscillations in response to extrinsic current pulses applied through the recording pipette. This response is analyzed as that of a damped harmonic oscillator. Oscillation frequency rises with membrane depolarization, from 80-160 Hz at resting potential to asymptotic values of 200-250 Hz. The sharpness of electrical tuning, denoted by the electrical quality factor, Q_e, is a bell-shaped function of membrane voltage, reaching a maximum value around eight at a membrane potential slightly positive to the resting potential.

In whole cells, three time-variant ionic currents are activated at voltages more positive than -60 to -50 mV; these are identified as a voltage-dependent, non-inactivating Ca current (I_ca), a voltage-dependent, transient K current (I_a), and a Ca-dependent K current (I_c). The C channel is identified in excised, inside-out membrane patches on the basis of its large conductance (130-200 pS), its selective permeability to Kover Na or Cl, and its activation by internal Ca ions and membrane depolarization. Analysis of open- and closed-lifetime distributions suggests that the C channel can assume at least two open and three closed kinetic states.

Exposing hair cells to external solutions that inhibit the Ca or C conductances degrades the electrical resonance properties measured under current-clamp conditions, while blocking the A conductance has no significant effect, providing evidence that only the Ca and C conductances participate in the resonance mechanism. To test the sufficiency of these two conductances to account for electrical resonance, a mathematical model is developed that describes I_ca, I_c, and intracellular Ca concentration during voltage-clamp steps. I_ca activation is approximated by a third-order Hodgkin-Huxley kinetic scheme. Ca entering the cell is assumed to be confined to a small submembrane compartment which contains an excess of Ca buffer; Ca leaves this space with first-order kinetics. The Ca- and voltage-dependent activation of C channels is described by a five-state kinetic scheme suggested by the results of single-channel observations. Parameter values in the model are adjusted to fit the waveforms of I_ca and I_c evoked by a series of voltage-clamp steps in a single cell. Having been thus constrained, the model correctly predicts the character of voltage oscillations produced by current-clamp steps, including the dependencies of oscillation frequency and Q_e on membrane voltage. The model shows quantitatively how the Ca and C conductances interact, via changes in intracellular Ca concentration, to produce electrical resonance in a vertebrate hair cell.

A transitividade verbal: uma revisão semântico-pragmática

Esta tese aborda o tema Transitividade Verbal em construções predicativas encontradas em corpus construído com textos jornalísticos impressos do Brasil. Os verbos são estudados segundo ocorrências retiradas de jornais de grande circulação em três capitais. Toma-se a semântica, a pragmática e a sintaxe como determinantes potenciais da transitividade verbal e aborda-se o tema segundo perspectiva histórica, ou seja, procura-se desenhar o percurso do tema nos estudos de língua portuguesa desde a sua primeira gramática, chegando-se, então, a reflexões mais atuais e também ao tratamento dispensado aos verbos e sua construção predicativa em dicionários e em gramáticas pedagógicas. O confronto com estudos acerca da língua espanhola também é motivo de atenção, devido à proximidade que o tema apresenta nas duas línguas. A partir desses estudos, buscou-se elaborar quadro sistemático e mais coerente dos verbos segundo a transitividade e construção predicativa, procurando aliar-se a base teórica consistente, apresentada pela tradição dos estudos gramaticais, às reflexões técnico-científicas acordadas com a realidade lingüística levantada a partir do corpus

Preliminary evidence of increased spawning aggregations of mutton snapper (Lutjanus analis) at Riley’s Hump two years after establishment of the Tortugas South Ecological Reserve

In this note we describe the re-formation of a spawning aggregation of mutton snapper (Lutjanus analis). A review of four consecutive years of survey data indicates that the aggregation may be increasing in size. Mutton snapper are distributed in the temperate and tropical waters of the western Atlantic Ocean from Florida to southeastern Brazil (Burton, 2002). Juveniles and subadults are found in a variety of habitats such as vegetated sand bottoms, bays, and mangrove estuaries (Allen, 1985). Adults are found offshore on coral reefs and other complex hardbottom habitat. They are solitary and wary fish, rarely found in groups or schools except during spawning aggregations (Domeier et al., 1996). Spawning occurs from May through July at Riley’s Hump (Domeier et al., 1996) and peaks in June, as indicated by gonadosomatic indices (M. Burton, unpubl. data). Mutton snapper are highly prized by Florida fishermen for their size and fighting ability, and the majority of landings occur from Cape Canaveral, through the Florida Keys, including the Dry Tortugas (Burton, 2002).

Comportamento territorial de Lipaugus lanioides (Aves: Cotingidae) em área de Floresta Atlântica na Ilha Grande, RJ

O comportamento territorial é uma estratégia de monopolização de recursos quando esses são essenciais para o sucesso reprodutivo de um organismo. Um território é uma área de uso exclusivo, defendido contra invasores coespecíficos de mesmo sexo, resultante da interação social entre vizinhos. A territorialidade exerce importante papel no sistema reprodutivo de uma espécie, pois influencia a participação do macho na reprodução. Nesses casos, as fêmeas podem obter vantagens diretas, como sítios de nidificação e cuidado parental. O comportamento territorial também exerce influência na regulação do tamanho populacional através de uma relação entre custos e benefícios individuais: em ambientes ótimos e com alta densidade populacional, os territórios são pequenos com pouca substituição, e jovens machos têm dificuldade para conseguirem estabelecer-se. O presente estudo teve como objetivo investigar aspectos comportamentais do tropeiro-da-serra, espécie rara e endêmica de Floresta Atlântica, com distribuição bastante restrita. Ao longo de 18 meses na Ilha Grande (RJ), analisamos seu comportamento territorial, mensuramos os tamanhos de territórios individuais de machos e realizamos estimativas de densidade populacional. O playback foi utilizado para atestar a presença de territorialidade na espécie, para simular a aproximação de coespecíficos (interações intraespecíficas) e para induzir o deslocamento dos indivíduos até os limites de seus territórios. Para investigar as respostas comportamentais à aproximação de invasores, analisamos quantitativamente as reações dos indivíduos a estímulos sonoros (vocalização espontânea e induzida pelo playback). Os territórios individuais foram definidos em duas estações reprodutivas através do método do Mínimo Polígono Convexo (MPC) em uma área equivalente a 20ha. A densidade populacional foi definida através do número de territórios encontrados e pelo número de indivíduos vistos/ouvidos por unidade de área através de transecções lineares. As vocalizações espontâneas e induzidas ocorreram somente entre os meses de agosto a janeiro, caracterizando uma estação reprodutiva bem definida. Durante este período, os machos tornaram-se solitários e agressivos com coespecíficos; na fase não-reprodutiva, entretanto, os indivíduos mostram-se sociáveis, forrageando em pequenos grupos de até quatro indivíduos. Os resultados indicam que o território é estabelecido para a monopolização de alimento e acesso às fêmeas. Essas observações sugerem que a espécie estudada é territorialista. Foram estimados sete territórios com valores entre 0,21ha e 0,73ha (0,43 + 0,16ha). Os indivíduos apresentaram fidelidade territorial, ocupando os mesmos territórios em duas estações reprodutivas. A densidade populacional de L. lanioides apresentou flutuações ao longo do ano, com os maiores valores encontrados durante a estação reprodutiva (variando entre 0,37 e 1,84 indivíduos/ha). Flutuações na densidade populacional podem apontar migrações altitudinais motivadas por variações na disponibilidade de recursos alimentares. Concluímos que o comportamento reprodutivo de L. lanioides não se enquadra no conceito de sistema reprodutivo em leks, conhecido em outros cotingídeos (ex. Lipaugus vociferans), no qual a corte é um comportamento social, com disputa por status de dominância, e o papel do macho resume-se à cópula sem benefícios diretos para as fêmeas. Dessa forma, os resultados do presente estudo trazem informações originais sobre a biologia de L. lanioides

Comportamento de forrageamento de Xiphorhynchus fuscus (Aves: Dendrocolaptidae): uma comparação entre áreas de Mata Atlântica de ilha e continente

Mudanças de nicho entre ilhas e continente, ou entre diferentes ilhas, incluem expansões de habitat e faixas mais amplas de estratos verticais de forrageamento. Organismos estão geralmente aptos a explorar apenas uma porção dos recursos que se encontra disponível no ambiente. A maneira como partilham esses recursos, além de definir seu nicho ecológico, pode indicar como as interações entre as espécies influenciam na estrutura da comunidade. Estas espécies, por sua vez, encontram-se associadas por suas relações de alimentação. Entre aves, diferentes espécies se associam para explorar recursos alimentares em agregações como a de espécies que seguem correição de formigas ou em bandos mistos. A associação de aves a bandos mistos tem sido relacionada à diminuição da predação e aumento da eficiência do forrageamento. Nesse tipo de associação, as espécies são categorizadas de acordo com a sua frequência e importância, e podem contribuir com a formação, coesão e manutenção do bando. O presente estudo teve como objetivo comparar o comportamento de forrageamento de Xiphorhynchus fuscus entre áreas de Mata Atlântica de ilha e continente a fim de investigar se existem diferenças em decorrência do isolamento. Foram realizadas transecções e observado o comportamento de forrageamento da espécie entre áreas de ilha e continente adjacente. Os resultados mostram uma diferença nos uso dos estratos verticais entre ilha e continente e entre indivíduos forrageando solitários e em bandos mistos de aves. A maior amplitude dos estratos verticais na ilha e a restrição deles no continente pela espécie, ao forragear solitariamente, indicam um provável efeito relacionado à competição. As diferenças entre o uso dos estratos verticais entre ilha e continente indicam a influência da composição das espécies em bandos mistos no estrato vertical utilizado por X. fuscus quando associado a estes. A menor adesão de X. fuscus a bandos mistos em ilha indica que a ausência de espécies de aves consideradas responsáveis pela associação das espécies e sua manutenção em bandos mistos seja responsável pela diferença encontrada em relação ao continente. Portanto, a diferença entre o número de espécies entre ilha e continente (com menor número na ilha) parece ser preponderante na utilização dos estratos verticais de forrageamento por X. fuscus estando ele associado a bandos mistos ou não

Remote Camera and Trapping Survey of the Deep-water Shrimps Heterocarpus laevigatus and H. ensifer and the Geryonid Crab Chaceon granulatus in Palau

Time-lapse remote photo-sequences at 73-700 m depth off Palau, Western Caroline Islands, show that the caridean shrimp Heterocarpus laevigatus tends to be a solitary animal, occurring below ~350 m, that gradually accumulates around bait sites over a prolonged period. A smaller speies, H. ensifer, tends to move erratically in swarms, appearing in large numbers in the upper part of its range (<250 m) during the evening crepuscular period and disappearing at dawn. Trapping and photsequence data indicate the depth range of H. ensifer (during daylight) is ~250-550 M, while H. laevigatus ranges from 350 m to at least 800 m, along with the geryonid crab Chaceon granulatus. Combined trapping for Heterocarpus laevigatus and Chaceon granulatus, using a three-chamber box-trap and extended soak times (48-72 hr), may be an appropriate technique for small-scale deep-water fisheries along forereef slopes of Indo-Pacific archipelagoes.

兰科槽舌兰属的系统学研究

槽舌兰属为兰科树兰亚科万代兰族指甲兰亚族植物，大部分种类为中国特有种，部分种类分布到越南、泰国、缅甸等国家和地区。长期以来，本属植物由于与近缘属间的界线模糊不清，而属内性状变异大，是兰科植物系统学研究的疑难属之一。本文通过对槽舌兰属及部分近缘属植物的形态地理学、细胞学、传粉生物学、分子系统学等研究，重新界定了槽舌兰属，确认该属植物的种类，提出一个新的属下分类系统，讨论了槽舌兰属属内和近缘属间的系统学关系，同时对槽舌兰属高山组植物的演化进行了探讨。 1．槽舌兰属及近缘属形态学性状 　　我们通过标本研究和野外观察，对槽舌兰属和近缘属植物的形态学性状及其变异式样进行了详细比较分析，重新评价各性状的分类学价值，认为蕊喙、蕊柱翅、花粉块类型等对于槽舌兰属与近缘属的划分具有重要意义;胼胝体类型、粘盘柄形状、距的类型、唇瓣中裂片边缘状况等对属下分类具有重要的意义;而中裂片、侧裂片和距的形态对槽舌兰属的种的划分具有重要的意义。传统上作为划分种依据的胼胝体的数目、花序上花的数目、茎的长短等在种内变异较大，不宜用作种划分的依据。 2. 槽舌兰属植物核型研究 　　我们报道了8种槽舌兰属植物的体细胞的染色体数目，其中6种为首次报道，并对其中7个种的核型进行初步分析。目前已进行研究的槽舌兰属植物的染色体数为2n=38，体细胞分裂中期的染色体长小于2 um, 染色体类型以中部和近中部着丝粒染色体为主，部分染色体成点状。槽舌兰属不同染色体数目相等、染色体形态和大小相似，从一个方面反映了槽舌兰属植物是一个单系类群。 3. 滇西槽舌兰（Holcoglossum rupestre）的传粉生物学研究 　　我们选择滇西槽舌兰的进行传粉生物学研究以探讨本属植物系统学和进化，发现滇西槽舌兰的传粉系统为兰科植物中少见的甲虫专化传粉系统，而且滇西槽舌兰的传粉系统处于一种不稳定的状态。弯腿金龟（Hybovalus bioculatus）是滇西槽舌兰唯一的传粉者，以两个不同的部位携带花粉团，即前腿和臀部，并存在着两种不同的传粉机制。滇西槽舌兰这种不稳定的传粉系统似乎表明该系统可能正处于转变阶段。繁殖系统的实验表明自然状况下滇西槽舌兰结实率由传粉率决定，而自然状况下低的结实率可能由两方面的原因导致：很低的传粉效率和有效的防止自花传粉机制。 4. 槽舌兰属植物的分子系统学研究 　　我们对9种槽舌兰属植物和2种万代兰属植物的叶绿体基因组trnL-F序列进行了测定，并从基因库下载了14种万代兰族植物和2种用作外类群的美洲附生兰亚科植物的trnL-F序列。测序结果发现槽舌兰属的trnL-F序列存在着很大的差异：H. lingulatum的trnL-F存在大片段的缺失，而H. kimballianum的trnL-F存在许多小片段的插入。分子系统学分析表明槽舌兰属为一单系类群，支持将Vanda subulifolia和V. amesiana转置入槽舌兰属中，强烈支持由H. sinicum、H. flavescens、H. rupestre和 H. weixiense构成槽舌兰属属内分支。 5．槽舌兰属的分类学修订 　　在广泛查阅国内外馆藏标本和开展多次野外调查的基础上，并结合细胞学和分子系统学研究结果，我们重新界定了槽舌兰属。该属植物的主要特征：茎短;叶肉质，细长半圆柱形，部分种叶略扁而成“V”形，其近轴面具一纵槽，先端渐尖，不裂;总状花序侧生，花疏生;花苞片比花梗和子房短;侧萼片或多或少呈镰形;花瓣通常具爪，与中萼片相似;唇瓣3裂;侧裂片直立;中裂片较大，基部常有附属物;蕊柱粗短，具翅，无蕊柱足或具很短的足;蕊喙2裂;花粉团蜡质，2个，球形，具裂隙。确定槽舌兰属目前包括11种（包括2个新种）：H. subulifolium、H. amesianum、H. kimballianum、H. lingulatum、H. omeiense、H. quasipinifolium、H. sinicum、H. rupestre、H. flavescens、H. wangii和H. weixiense。 H. tangii和Vanda saprophytica被分别处理为H. lingulatum与H. kimballianum的异名，而H. tsii的分类学地位尚有待进一步研究。同时在我们研究的基础上，提出槽舌兰属一个新属下的分类系统： 槽舌兰属 Holcoglossum 　　短距亚属 Holcoglossum subgen. Amesianum 　　H. subulifolium，H. amesianum; 槽舌兰亚属Holcoglossum subgen. Holcoglossum 　槽舌兰组Holcoglossum sect. Holcoglossum 　　H. kimballianum，H. lingulatum，H. wangii，H. omeiense，H. quasipinfolium; 高山组Holcoglossum sect. Sinicum 　H. sinicum，H. rupestre，H. flavescens，H. weixiense。 6．槽舌兰属属内和近缘属间系统学关系探讨 　　通过广泛的形态地理研究并结合传粉生物学和分子系统学研究结果，我们对槽舌兰属属内和属间关系进行的探讨。槽舌兰属短距亚属与万代兰属和指甲兰属比较接近，是槽舌兰属中比较原始的类群; 槽舌兰组植物的分布中心介于短距亚属和高山组分布中心之间，而该组植物的许多性状也表现出过渡性质。在‘Aerides-Vanda alliance’中，我们认为钻喙兰属和万代兰属是该类群中比较原始的属，而鸟舌兰属（Ascocentrum）可能是介于指甲兰属和举喙兰属（Seidenfadenia）之间，支持传统的观点认为Papilionanthe位于Vanda和Aerides之间但更接近于Aerides，但同时我们认为举喙兰属可能是‘Aerides-Vanda alliance’中最为特化的类群。 7． 高山组所属物种形成探讨 　　槽舌兰属高山组的四个种均为中国特有植物，主要分布云南西北部地区，其中H. weixiense、 H. rupestre、H. sinicum3个种只局限分布在云南的西北部地区。尽管高山组各个种比较相似，但形态上已经分化，生境也不同而且存在着对应关系。细胞学实验结果发现槽舌兰属高山组的四种植物均为二倍体（2n=38），与槽舌兰属的其他种类一致，这表明该组植物在横断山区的分化时染色体的数目并没有变化，高山组植物的三种横断地区特有植物可能为裂生特有。高山组4个种的1300bp的trnL-F总共只有10个碱基的差异，在trnL-F分支图中，高山组分支作为单系类群得到强有力的支持（BP=94%）。高山组植物trnL-F序列微小的差别反映了该组植物可能是在近期通过快速物种形成进行分化的。这些资料说明槽舌兰属高山组植物是近期通过适应辐射进行分化以适应不同生境，而且可能是生境和传粉系统共同驱动下形成的。

Los elefantes marinos de península Valdés

Durante la primavera austral, la Península Valdés (Chubut, Argentina) es el escenario de la masiva visita del elefante marino sudamericano (Otaria flavescens). Se trata de la temporada reproductiva. El recuento año tras año de este conjunto migrante es un trabajo indispensable para conocer la dinámica de la población. Los censos poblacionales terrestres ofrecen un invalorable conocimiento de sus fluctuaciones y migraciones. Se brindan particularidades de la elefantería de Valdés y sus poblaciones, aspectos biológicos relevantes y otras lecturas sugeridas.

Comportamiento reproductivo del lobo marino sudamericano

En la evolución de los lobos sudamericanos, son varios los factores que modelaran sus comportamientos reproductivos y las diferencias entre los sexos que podemos observar en la naturaleza. Una de las principales características es la capacidad de desarrollar un comportamiento reproductivo plástico y cambiante. La influencia de las variaciones ecológicas sobre los sistemas reproductivos modelan las características de las estrategias reproductivas en los pinnípedos, y el lobo marino sudamericano es un ejemplo de ello. Se describen estrategias reproductivas y del comportamiento de la especie Otaria flavescens que ha sido estudiada en detalle en la peníncula de Valdés, Argentina (océano Atlántico sudoccidental).

Tsunami wave runup on the clustered islands using boussinesq-type model

This paper describes the implementation of the Boussinesq-type model and extends its application to the tsunami wave runup on the clustered islands (multiple adjacent conical islands), in turn, an extensively validated two-dimensional Boussinesq-type model is employed to examine the interaction between a propagating solitary wave and multiple idealised conical islands, with particular emphasis on a combination effect of two adjustable parameters for spacing interval/diameter ratio between the adjacent conical islands, S/D, and the rotating angle of the structural configuration,θ on maximum soliton runup heights. An extensive parameter study concerning the combination effect of alteringθ and S/D on the maximum soliton runup with the multi-conical islands is subsequently carried out and the distributions of the maximum runup heights on each conical island are obtained and compared for the twin-island cases. The worst case study is performed for each case in respect of the enhancement in the maximum wave runup heights by the multi-conical islands. It is found that the nonlinear wave diffraction, reflection and refraction play a significant role in varying the maximum soliton runup heights on multiconical islands. The comparatively large maximum soliton runups are generally predicted for the merged and bottom mounted clusteredislands. Furthermore, the joints of the clustered-merged islands are demonstrated to suffer the most of the tsunami wave attack. The conical islands that position in the shadow regions behind the surrounding islands are found to withstand relatively less extreme wave impact. Although, these numerical investigations are considerable simplifications of the multi conical islands, they give a critical insight into certain important hydrodynamic characteristics of the interaction between an extreme wave event and a group of clustered conical islands, and thus providing a useful engineering guidance for extreme wave mitigation and coastal development. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE).

Interaction between tsunami waves and isolated conical Islands

A newly developed computer model, which solves the horizontal two-dimensional Boussinesq equations using a total variation diminishing Lax-Wendroff scheme, has been used to study the runup of solitary waves, with various heights, on idealized conical islands consisting of side slopes of different angles. This numerical model has first been validated against high-quality laboratory measurements of solitary wave runups on a uniform plane slope and on an isoliated conical island, with satisfactory agreement being achieved. An extensive parametric study concerning the effects of the wave height and island slope on the solitary wave runup has subsequently been carried out. Strong wave shoaling and diffraction effects have been observed for all the cases investigated. The relationship between the runup height and wave height has been obtained and compared with that for the case on uniform plane slopes. It has been found that the runup on a conical island is generally lower than that on a uniform plane slope, as a result of the two-dimensional effect. The correlation between the runup with the side slope of an island has also been identified, with higher runups on milder slopes. This comprehensive study on the soliton runup on islands is relevant to the protection of coastal and inland regions from extreme wave attacks. © the Coastal Education & Research Foundation 2012.