41 research outputs found
The natural history of pollination and mating in bird-pollinated Babiana (Iridaceae)
No full textBackground and Aims Floral variation, pollination biology and mating patterns were investigated in sunbird-pollinated Babiana (Iridaceae) species endemic to the Western Cape of South Africa. The group includes several taxa with specialized bird perches and it has been proposed that these function to promote cross-pollination. Methods Pollinator observations were conducted in 12 populations of five taxa (B. ringens subspp. ringens, australis, B. hirsuta, B. avicularis, B. carminea) and geographic variation in morphological traits investigated in the widespread B. ringens. Experimental pollinations were used to determine the compatibility status, facility for autonomous self-pollination and intensity of pollen limitation in six populations of four taxa. Allozyme markers were employed to investigate mating patterns in four populations of three species. Key Results Sunbirds were the primary pollinators of the five Babiana taxa investigated. Correlated geographical variation in perch size, flower size and stigmaanther separation was evident among B. ringens populations. Experimental pollinations demonstrated that B. ringens and B. avicularis were self-compatible with variation in levels of autonomous self-pollination and weak or no pollen limitation of seed set. In contrast, B. hirsuta was self-incompatible and chronically pollen limited. Estimates of outcrossing rate indicated mixed mating with substantial self-fertilization in all species investigated. Conclusions Despite the possession of specialized bird perches in B. ringens and B. avicularis, these structures do not prevent considerable selfing from occurring, probably as a result of autonomous self-pollination. In eastern populations of B. ringens, smaller flowers and reduced herkogamy appear to be associated with a shift to predominant selfing. Relaxed selection on perch function due to increased selfing may explain the increased incidence of apical flowers in some populations. © The Author 2011
Design of a statically balanced mechanism using magnets and springs
No full textThe current work presents a statically balanced system with novel design, which incorporates compression springs as a positive stiffness and magnets as a negative stiffness. The mechanism varies the force in the positive stiffness elements from zero to maximum. In this way, the balancing system can be used as a force amplifier. The goal of the current design is to be used in a friction brake. A specific magnet configuration is used to achieve a relatively linear force-distance relationship. The configuration consist of three block-magnets, from which one magnet translates and two magnets are placed in a stationary steel U-shape. This force-distance relationship is balanced by a piecewise linear characteristic achieved by using multiple compression springs with different action-initiation points. The proof-of-concept build consists of a lever mechanism with a lever arm of 100 mm, one set of magnets and three compression springs. By varying the position of the lever from to 5.04, the force in the springs is varied between 0N and 872 N. Experimental evaluation of the prototype reveals a minimum of 97% force reduction in the prototype compared to the unbalanced prototype.BioMechanical DesignBioMechanical EngineeringMechanical, Maritime and Materials Engineerin
Cadwell W. Raines and His Wife in the Texas State Library
No full textMr. and Mrs. Cadwell W. Raines in the Texas State Library in Austin. Mrs. Raines was the daughter of S.C.H. Witten of Colleyville. Cadwell W. Raines was born in Macon, Ga. Sept. 16, 1839. and died in Austin on Aug. 2, 1906. He was a confederate soldier, teacher, editor, county judge for Van Zandt County 1876-78, and for Wood County 1888-1890; author, Texas state librarian 1891-1895, and 1897-1906
An experimental evaluation of self-interference in Narcissus assoanus: functional and evolutionary implications
No full textInternational audienceFloral traits that reduce self-pollination in hermaphroditic plants have usually been interpreted as mechanisms that limit the genetic consequences of self-fertilization. However, the avoidance of sexual conflict between female and male function (self-interference) may also represent an important selection pressure for the evolution of floral traits, particularly in self-incompatible species. Here, we use experimental manipulations to investigate self-interference in Narcissus assoanus, a self-incompatible species with a stigma-height dimorphism in which the degree of spatial separation between sex organs (herkogamy) differs strikingly between the long- and short-styled morphs (hereafter L- and S-morphs). We predicted that weak herkogamy in the L-morph would cause greater self-pollination and hence self-interference. Experimental self-pollination reduced seed set when it occurred prior to, or simultaneously with, cross-pollination in the L-morph, but only if it occurred prior to cross-pollination in the S-morph. In the field, autonomous self-pollination was greater in the L-morph than the S-morph, but we found no evidence that self-interference reduced maternal or paternal fitness in either morph. One-day-old flowers of the L-morph have reduced stigma receptivity and hence exhibit protandry, whereas stigma receptivity and anther dehiscence are concurrent in the S-morph. This suggests that the two style morphs have alternative strategies for reducing self-interference: dichogamy in the L-morph and herkogamy in the S-morph. These results provide insight into the mechanisms that reduce sexual conflict in hermaphrodite plants and are of significance for understanding the evolution and maintenance of sexual polymorphisms
Une évaluation expérimentale de l'auto-interférence liée à l'auto-pollen chez Narcissus assoanus : implications fonctionnelles et évolutives
No full textInternational audienc
Une évaluation expérimentale de l'auto-interférence liée à l'auto-pollen chez Narcissus assoanus : implications fonctionnelles et évolutives
No full textInternational audienc
The effect of mammalian herbivory on inflorescence architecture in ornithophilous babiana (Iridaceae): Implications for the evolution of a bird perch
No full textPremise of the study: The showiness of floral displays is usually explained as an adaptation to attract pollinators. However, selection for less attractive displays imposed by non-pollinating agents, particularly herbivores, may balance pollinator-driven selection for highly visible inflorescences. We investigated whether inflorescence architecture, particularly the unusual groundlevel flowering associated with a specialized bird perch in Babiana ringens may have originated, in part, as an adaptive response to mammalian herbivory. Methods: We measured levels of herbivory by antelope in populations of B. hirsuta, the putative sister species of B. ringens, which possesses the likely ancestral form of inflorescence architecture. To test for position-dependent effects of herbivory on flowers, we compared the herbivory rates and seed production of manipulated inflorescences in a field experiment. We predicted that flowers at the base of inflorescences would suffer less herbivory than those in apical positions. Results: We found herbivore damage to flowers in 50% of naturally occurring B. hirsuta plants. Manipulated inflorescences with only basal flowers, and consequently similar inflorescence architecture to B. ringens, experienced significantly lower herbivory and higher seed set than inflorescences manipulated to have only apical flowers. Conclusions: Our results are consistent with the hypothesis that position-dependent herbivory on inflorescences could have played a role in the evolution of inflorescence design. More specifically, position-dependent herbivory may have selected for the loss of apical flowers. Position-dependent herbivory may have contributed toward the evolution of a naked inflorescence axis, a structure that characterizes B. ringens and functions as a bird perch facilitating cross-pollination by sunbirds. © 2012 Botanical Society of America
Falencia multiplas de orgaos. Avaliacao critica da experiencia pessoal em dois periodos de dez anos
No full textDid M.O.F. of the seventies occur in subsequent years in I.C.U? Are they peculiar to surgical and post-traumatic patients? Are they frequent in non-surgical or non-traumatic patients in the seventies, eighties and nineties? The author studied the incidence and prevalence of M.O.F. in two different periods, 1966 to 1975, 1981 to 1990, in two I.C.U. of his own direction. The first in C.C.H. and the second in S.C.H. In the first one, critical patients, predominantly medical were studied, in the second, critical surgical, medical and high-risk patients. In C.C.H. 715 patients, 477 with R.F. and 238 with A.R.F. as initial insults were studied. The patients of the first group included 147 A.T., 76 N.B.T., 40 G.B., 30 N., 52 C.N.S.I., 42 C.O.D., 28 P., 22 L.T., 22 B.A., 27 T.T.. The A.R.F. cases included 59 G.N., 41 O.N., 41 G.L.N., 52 T.N., 45 P.S.N.. In the second period of the 4420 admitted to the I.C.U. the great majority prophilatically post-surgery, factors associated with survival were studied in 763, 473 critical and 289 high-risk. In the whole 343 were surgical and 419 medical. Global mortality for R.F., C.C.H. patients was 41,6%. The incidence of failures in 2,3,4, and more organs occurred in 257 patients. Mortality was: in 166 patients with 2 O.F. 74, in 69 with 3-44; in 22 with 4 or more- 19. In A.R.F. with global mortality of 46,2% in 56 with 2 O.F., 36 survived; in 59 with 3,18; in 15 with 4-2. All the patients with R.F. were studied retrospectively with APACHA and TISS in C.C.H.. The A.R.F. patients were not studied with these methods. The statistical results obtained with discriminant analysis and logistic regression entering with M.O.F. were better than those achieved with APACHE and TISS. In S.C.H., of the 4420 patients, 618 died, 57% of them with one O.F. and 43% with M.O.F. The failures in deceased patients were R.F. in 61,6% C.V.F. 52,3%; A.R.F. 34,5%; sepsis 18,8%; C.N.S. 14,3%; liver 10,2%; blood 5,7%. In 343 surgical and in 419 medical, 455 had A.R.F., 56 of them being high-risk patients. The mortality of medical cases with A.R.F. was 21,8% and of surgical ones 16,1%. In high-risk patients, R.F. occurred in 105,40 had one O.F.; 107 two or more and 41 none. In the M.O.F. patients mortality was 50%. In C.T.R.F. in high medical or surgical risk, the highest mortality was associated with hemorragic and respiratory insults. In 289 high-risk patients APACHE and TISS were prospectivelly applied. Th O.F. mortality in both hospitals was much lower than the mortality in M.O.F. patients. Mortality associated with M.O.F. in patients with a prevous O.F. varied with the new insults. Cardiac insults associated with R.F. in C.C.H. had a mortality of 57,6% and with A.R.F. of 73,3%. Logistic regression showed the importance of each individual insult. In A.R.F., in both hospitals cardiac, septic, respiratory and digestive were the most severe. In C.C.H. the largest mortality in R.F. occurred in the first 4 days; in A.R.F, in the first 15 and only 50% survived at the end of 60 days. In S.C.H. the mortality was more distributed in time, declining slowly in A.R.F. to 35% in 150 days. In high-risk patients in S.C.H. it fell down in pleteau till 50 days. In the patients of this group, 25 occupied half of the internment days and had the highest mortality Besides the type of the insults, the ethiology of the initial process and age were of high importance. These factors may contribute to the development of M.O.F. in a population of the eighties and nineties with characteristics different from the sixties, namely in high-risk patientsAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga
Forced Torsional Vibration of a Monopile for Its Extraction
No full textThe offshore monopile decommissioning demand will become definite in the coming years. Our responsibility is to ensure the rights and duties of other legitimate uses by completely removing the ageing monopile from the seabed to continuously redeveloping offshore wind farms within the same location. The growing number of past, present, and future monopile installations opens up the challenges and opportunities to be responsible and lead the decommissioning market. With the goal of complete removal, a novel GDP technique can be the win-win solution for offshore wind operators and contractors to extract the monopiles completely from the seabed using torsional and axial vibrationThis thesis seeks to understand the torque and normal force to safely clamp a monopile during a torsional vibration so that the monopile continuously slips over the soil. Gradual soil failure along the pile-soil interface's full depth due to the monopile's torsional motion is a possible theory to explain the failure mechanism. When an upper part of the pile successfully moves relative to the soil, kinetic friction occurs until the soil resistance is larger than the shearing at one point. If more shearing is added by adding more torque, more layers below will be broken while the upper part keeps sliding due to lower friction than static friction. While the linear elastic theory of solid and thin shell bodies is used within a 3D FE modelling in Ansys to couple the soil and pile, the clamping force due to the GDP shaker is decoupled from the analysis. Failure criterion is defined outside the simulation so that the gradual soil failure is done through several simulations assuming discrete soil layers.The FE model is constructed and verified by analytical calculation through the semi-infinite cavity-pile-soil, wave reflection, and finite cavity-pile-soil-spring-dashpot problems. Several cases of gradual soil failure are simulated and show that the torque amplitudes form a distribution. Firstly, a probabilistic sense is proposed to interpret the torque amplitude and search for the optimum depth of the soil failure. Secondly, a convergence check is made with the help of an analytical shell-spring by considering more soil elements by virtue of good correlation of the shear stress between the analytical and FE model. It eventually suggests that a convergence of the torque amplitude can be achieved, which reinforces the theory of gradual soil failure. The interpretation suggests that the current GDP shaker is one step closer for a monopile extraction test with typical monopile dimensions that correspond to a typical 1 m diameter. A first approximation of the required torque and clamping force is then proposed to benefit the analytical model for larger diameters up to 6 m.Offshore and Dredging Engineering | Bottom Founded Structures, Arctic and Win
