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Convex
Terms modified by Convex Selected AbstractsNeuro-mesodermal patterns in artificially deformed embryonic explants: A role for mechano-geometry in tissue differentiationDEVELOPMENTAL DYNAMICS, Issue 3 2010E.S. Kornikova Abstract The mutual arrangement of neural and mesodermal rudiments in artificially bent double explants of Xenopus laevis suprablastoporal areas was compared with that of intact explants. While some of the bent explants straightened or became spherical, most retained and actively reinforced the imposed curvature, creating folds on their concave sides and expanding convex surfaces. In the intact explants, the arrangement of neural and mesodermal rudiments exhibited a distinct antero-posterior polarity, with some variability. In the bent explants, this polarity was lost: the neural rudiments were shifted towards concave while the mesodermal tissues moved towards the convex side, embracing the neural rudiments in a horseshoe-shaped manner. We associate these drastic changes in neuro-mesodermal patterning with the active extension and contraction of the convex and concave sides, respectively, triggered by the imposed deformations. We speculate that similar events are responsible for the establishment of neuro-mesodermal patterns during normal development. Developmental Dynamics 239:885,896, 2010. © 2010 Wiley-Liss, Inc. [source] STANDARDIZATION OF ENDOSCOPIC ULTRASONOGRAPHY PROCEDURES FOR THE PANCREAS USING RADIAL and CONVEX methodsDIGESTIVE ENDOSCOPY, Issue 2002Yoshiki Hirooka We describe the standard endoscopic ultrasonography (EUS) procedure of the pancreas used in our institute. Both radial scanning and convex (or linear) scanning methods have valid uses, so these two methods will coexist in the future. Physicians learning EUS need to master both types. It is important to standardize both types of EUS procedure. Generally, physicians persist in the method mastered first and don't make use of the other method. In order to plan the standardization of EUS procedures, it may be reasonable to standardize the procedures of both type EUS simultaneously, comparing radial scan mode and linear (convex) scan mode. Here we demonstrate our standard procedures for both EUS modes, mainly emphasizing the visualization maneuver of the pancreas. [source] A low-dimensional physically based model of hydrologic control of shallow landsliding on complex hillslopesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2008Ali Talebi Abstract Hillslopes have complex three-dimensional shapes that are characterized by their plan shape, profile curvature of surface and bedrock, and soil depth. To investigate the stability of complex hillslopes (with different slope curvatures and plan shapes), we combine the hillslope-storage Boussinesq (HSB) model with the infinite slope stability method. The HSB model is based on the continuity and Darcy equations expressed in terms of storage along the hillslope. Solutions of the HSB equation account explicitly for plan shape by introducing the hillslope width function and for profile curvature through the bedrock slope angle and the hillslope soil depth function. The presented model is composed of three parts: a topography model conceptualizing three-dimensional soil mantled landscapes, a dynamic hydrology model for shallow subsurface flow and water table depth (HSB model) and an infinite slope stability method based on the Mohr,Coulomb failure law. The resulting hillslope-storage Boussinesq stability model (HSB-SM) is able to simulate rain-induced shallow landsliding on hillslopes with non-constant bedrock slope and non-parallel plan shape. We apply the model to nine characteristic hillslope types with three different profile curvatures (concave, straight, convex) and three different plan shapes (convergent, parallel, divergent). In the presented model, the unsaturated storage has been calculated based on the unit head gradient assumption. To relax this assumption and to investigate the effect of neglecting the variations of unsaturated storage on the assessment of slope stability in the transient case, we also combine a coupled model of saturated and unsaturated storage and the infinite slope stability method. The results show that the variations of the unsaturated zone storage do not play a critical role in hillslope stability. Therefore, it can be concluded that the presented dynamic slope stability model (HSB-SM) can be used safely for slope stability analysis on complex hillslopes. Our results show that after a certain period of rainfall the convergent hillslopes with concave and straight profiles become unstable more quickly than others, whilst divergent convex hillslopes remain stable (even after intense rainfall). In addition, the relation between subsurface flow and hillslope stability has been investigated. Our analyses show that the minimum safety factor (FS) occurs when the rate of subsurface flow is a maximum. In fact, by increasing the subsurface flow, stability decreases for all hillslope shapes. Copyright © 2008 John Wiley & Sons, Ltd. [source] The Impact of Uncertainty ShocksECONOMETRICA, Issue 3 2009Nicholas Bloom Uncertainty appears to jump up after major shocks like the Cuban Missile crisis, the assassination of JFK, the OPEC I oil-price shock, and the 9/11 terrorist attacks. This paper offers a structural framework to analyze the impact of these uncertainty shocks. I build a model with a time-varying second moment, which is numerically solved and estimated using firm-level data. The parameterized model is then used to simulate a macro uncertainty shock, which produces a rapid drop and rebound in aggregate output and employment. This occurs because higher uncertainty causes firms to temporarily pause their investment and hiring. Productivity growth also falls because this pause in activity freezes reallocation across units. In the medium term the increased volatility from the shock induces an overshoot in output, employment, and productivity. Thus, uncertainty shocks generate short sharp recessions and recoveries. This simulated impact of an uncertainty shock is compared to vector autoregression estimations on actual data, showing a good match in both magnitude and timing. The paper also jointly estimates labor and capital adjustment costs (both convex and nonconvex). Ignoring capital adjustment costs is shown to lead to substantial bias, while ignoring labor adjustment costs does not. [source] Numerical modeling of the Joule heating effect on electrokinetic flow focusingELECTROPHORESIS, Issue 10 2006Kuan-Da Huang Abstract In electrokinetically driven microfluidic systems, the driving voltage applied during operation tends to induce a Joule heating effect in the buffer solution. This heat source alters the solution's characteristics and changes both the electrical potential field and the velocity field during the transport process. This study performs a series of numerical simulations to investigate the Joule heating effect and analyzes its influence on the electrokinetic focusing performance. The results indicate that the Joule heating effect causes the diffusion coefficient of the sample to increase, the potential distribution to change, and the flow velocity field to adopt a nonuniform profile. These variations are particularly pronounced under tighter focusing conditions and at higher applied electrical intensities. In numerical investigations, it is found that the focused bandwidth broadens because thermal diffusion effect is enhanced by Joule heating. The variation in the potential distribution induces a nonuniform flow field and causes the focused bandwidth to tighten and broaden alternately as a result of the convex and concave velocity flow profiles, respectively. The present results confirm that the Joule heating effect exerts a considerable influence on the electrokinetic focusing ratio. [source] Testing the boolean hypothesis in the non-convex case when a bounded grain can be assumedENVIRONMETRICS, Issue 2 2008J. Chad Abstract Spatial independence of objects is a strong hypothesis when using boolean models. Methods to test it have then been developed, but only when the objects are convex. We propose here to replace this assumption by a bound assumption of the objects which can be more easily assumed when modeling spatial patterns in ecology and agricultural science. A test is then proposed, based on the length of the voids of the intersection between transect lines and a dilation of the original process related to the bound value. Its application is shown to several examples, together with its extension to an epidemiological case on orchards, where this problem comes from. Copyright © 2007 John Wiley & Sons, Ltd. [source] EXPERIMENTAL EVIDENCE FOR MULTIVARIATE STABILIZING SEXUAL SELECTIONEVOLUTION, Issue 4 2005Robert Brooks Abstract Stabilizing selection is a fundamental concept in evolutionary biology. In the presence of a single intermediate optimum phenotype (fitness peak) on the fitness surface, stabilizing selection should cause the population to evolve toward such a peak. This prediction has seldom been tested, particularly for suites of correlated traits. The lack of tests for an evolutionary match between population means and adaptive peaks may be due, at least in part, to problems associated with empirically detecting multivariate stabilizing selection and with testing whether population means are at the peak of multivariate fitness surfaces. Here we show how canonical analysis of the fitness surface, combined with the estimation of confidence regions for stationary points on quadratic response surfaces, may be used to define multivariate stabilizing selection on a suite of traits and to establish whether natural populations reside on the multivariate peak. We manufactured artificial advertisement calls of the male cricket Teleogryllus commodus and played them back to females in laboratory phonotaxis trials to estimate the linear and nonlinear sexual selection that female phonotactic choice imposes on male call structure. Significant nonlinear selection on the major axes of the fitness surface was convex in nature and displayed an intermediate optimum, indicating multivariate stabilizing selection. The mean phenotypes of four independent samples of males, from the same population as the females used in phonotaxis trials, were within the 95% confidence region for the fitness peak. These experiments indicate that stabilizing sexual selection may play an important role in the evolution of male call properties in natural populations of T. commodus. [source] THE EVOLUTION OF GENETIC CANALIZATION UNDER FLUCTUATING SELECTIONEVOLUTION, Issue 1 2000Tadeusz J. Kawecki Abstract., If the direction of selection changes from generation to generation, the ability to respond to selection is maladaptive: the response to selection in one generation leads to reduced fitness in the next. Because the response is determined by the amount of genetic variance expressed at the phenotypic level, rapidly fluctuating selection should favor modifier genes that reduce the phenotypic effect of alleles segregating at structural loci underlying the trait. Such reduction in phenotypic expression of genetic variation has been named "genetic canalization." I support this argument with a series of two- and multilocus models with alternating linear selection and Gaussian selection with fluctuating optimum. A canalizing modifier gene affects the fitness of its carriers in three ways: (1) it reduces the phenotypic consequences of genetic response to previous selection; (2) it reduces the genetic response to selection, which is manifested as linkage disequilibrium between the modifier and structural loci; and (3) it reduces the phenotypic variance. The first two effects reduce fitness under directional selection sustained for several generations, but improve fitness when the direction of selection has just been reversed. The net effect tends to favor a canalizing modifier under rapidly fluctuating selection regimes (period of eight generations or less). The third effect improves fitness of the modifier allele if the fitness function is convex and reduces it if the function is concave. Under fluctuating Gaussian selection, the population is more likely to experience the concave portion of the fitness function when selection is stronger. Therefore, only weak to moderately strong fluctuating Gaussian selection favors genetic canalization. This paper considerably broadens the conditions that favor genetic canalization, which so far has only been postulated to evolve under long-term stabilizing selection. [source] Seed characters and testa sculptures of some Iranian Allium L. species (Alliaceae)FEDDES REPERTORIUM, Issue 5-6 2009Fatemeh Neshati Seeds taken from herbarium specimens of 20 Allium taxa were investigated. The seeds of all species were black ranging from 1.7 mm (A. lamondiae) to 4 mm (A. altissimum and A. stipitatum) in length and 1 mm (A. lamondiae) to 3 mm (A. altissimum) in width. So, A. lamondiae had the smallest and A. altissimum the largest seeds. In the mean, the members of subg. Melanocrommyum had somewhat larger and the species of sect. Avulsea somewhat smaller seeds than most species belonging to other groups. The shape was generally ovate or variants of it and showed only slight differences between members of different sections. The seed coat pattern was more variable. Most common were convex, granulate periclinal walls bearing several verrucae. Only A. borszczowii showed flat, densely granulate periclinal walls without verrucae, and A. bungei and A. joharchii had somewhat verruca-like aggregating grana. The majority of the species investigated showed S-like, rarely Omega-like, undulated anticlinal walls with variable wavelengths and amplitudes. The testa cells of A. joharchii showed transitions to straight anticlinal walls. More or less straight anticlinal walls in A. kopetdagense, A. paradoxum, A. barsczewskii, and A. scabriscapum were connected with the presence of a strip-like widened and transversally striated intercellular region covering these walls. The seed coat pattern of most species corresponded well to earlier reports of the same or closely related species, or was at least already reported for not related Allium species. Only A. borszczowii and A. monophyllum displayed testa types earlier not reported. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Non-linearity in the cost-effectiveness frontierHEALTH ECONOMICS, Issue 6 2006Joanne Lord Abstract Conventional cost-effectiveness decision rules rely on the assumptions that all health care programmes are divisible and exhibit constant returns to scale for a homogeneous population; hence, the path between adjacent programmes on a cost-effectiveness frontier must be linear. In this paper we build a framework to analyse non-linear ,expansion' paths. We model the impact of two key sources of non-linearity: economies of scale or scope in the production of health care; and prioritisation of patients who are most likely to benefit from more expensive and more effective treatments. We conclude that the expansion path might be linear, convex or concave, depending on the situation. The path might also exhibit vertical discontinuity due to fixed costs or horizontal discontinuity due to indivisibility. The efficiency of resource allocation might be improved by empirical estimation of expansion paths. We discuss the advantages and disadvantages of this approach compared with a standard stratified analysis. Copyright © 2006 John Wiley & Sons, Ltd. [source] Infiltration into effluent irrigation-induced repellent soils and the dependence of repellency on ambient relative humidityHYDROLOGICAL PROCESSES, Issue 17 2007R. Wallach Abstract As a result of water scarcity and as a means of wastewater disposal, reuse of treated sewage effluent in irrigated agriculture is practiced worldwide. Among the detrimental aspects of wastewater re-use in agriculture is the possibility that soils will be rendered water repellent. The current study focuses on time dependent variation of infiltration rate in effluent-induced repellent soils, and time dependent variation in water repellency at different levels of ambient relative humidity (RH). The shape of the cumulative infiltration curve of water was found to depend on the repellency degree (concave for wettable and slightly repellent soils, convex for severely repellent soil). Compared with infiltration rates in the wettable and slightly repellent soils, infiltration rates in the severely repellent soil were very low at the beginning and then increased. When the liquid-vapor surface tension was reduced by means of ethanol addition to the infiltrating solution, the cumulative infiltration curve of the severely repellent soil also became concave. Repellency degree (as measured by WDPT) was found to be essentially constant over a large range of ambient RH values (<10 , ,81%), and to increase sharply at values above 90%. The relative increase in water drop penetration time (WDPT) at high RH was greatest for the least repellent soil (10-fold increase in WDPT), and least for the most repellent soil (2-fold increase in WDPT). At RH > 90%, the time to reach equilibrium with respect to WDPT and soil moisture content was similar. In contrast, at values of ambient RH ranging from < 10 to 81%, WDPT was invariant over the course of reaching equilibrium with respect to moisture content. However, after reaching moisture content equilibrium, WDPT declined with increasing time. Copyright © 2007 John Wiley & Sons, Ltd. [source] A new stereo-analytical method for determination of removal blocks in discontinuous rock massesINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 10 2003Zixin Zhang Abstract The paper provides a new stereo-analytical method, which is a combination of the stereographic method and analytical methods, to separate finite removable blocks from the infinite and tapered blocks in discontinuous rock masses. The methodology has applicability to both convex and concave blocks. Application of the methodology is illustrated through examples. Addition of this method to the existing block theory procedures available in the literature improves the capability of block theory in solving practical problems in rock engineering. Copyright © 2003 John Wiley & Sons, Ltd. [source] Semi-adaptive control of convexly parametrized systems with application to temperature regulation of chemical reactorsINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 4 2001Alexander Fradkov In this paper, we are interested in the problem of adaptive control of non-linearly parametrized systems. We investigate the viability of defining a stabilizing parameter update law for the case when the plant model is convex on the uncertain parameters. We show that, when the only prior knowledge is convexity, there does not exist an adaptation law,derivable from the standard separable Lyapunov function technique of Parks,applicable for all the state space. Therefore, we propose a semi-adaptive state feedback controller where adaptation takes place only in the region of the state space where convexity can be used to reduce parameter uncertainty. In the remaining part of the state space we freeze the adaptation and switch to a robust controller. This scheme ensures semi-global stability for convexly parametrized non-linear systems with matched uncertainty. The proposed controller is then applied to the problem of temperature regulation of continuous stirred exothermic chemical reactors where reaction heat is convex in the uncertain parameters. Copyright © 2001 John Wiley & Sons, Ltd. [source] On convexity of MQAM's and MPAM's bit error probability functionsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 11 2009M. Naeem Abstract For MQAM and MPAM with practical values of M and Gray mapping, we provide a rigorous proof that the associated bit error probability (BEP) functions are convex of the signal-to-noise ratio per symbol. The proof employs Taylor series expansions of the BEP functions' second derivatives and term-by-term comparisons between positive and negative terms. Convexity results are useful for optimizing communication systems as in optimizing adaptive transmission policies. Copyright © 2009 John Wiley & Sons, Ltd. [source] A closer look at the relationship between life expectancy and economic growthINTERNATIONAL JOURNAL OF ECONOMIC THEORY, Issue 2 2009Théophile T. Azomahou O41; I20; J10 We first provide a nonparametric inference of the relationship between life expectancy and economic growth using historical data for 18 countries over the period 1820,2005. The obtained shape indicates convexity for low enough values of life expectancy and concavity for large enough values. We then study this relationship using a benchmark model combining "perpetual youth" and learning-by-investing. The generated relationship between life expectancy and economic growth is shown to be strictly increasing and concave. We finally examine two models departing from "perpetual youth" by assuming successively age-dependent earnings and age-dependent survival probabilities. With age-dependent earnings, the obtained relationship is hump-shaped, whereas age-dependent survival laws reproduce the convex,concave shape detected in prior empirical study. [source] No-arbitrage condition and existence of equilibrium in asset markets with a continuum of tradersINTERNATIONAL JOURNAL OF ECONOMIC THEORY, Issue 1 2005Cuong Le Van C62 In the present paper, we prove that a no-arbitrage condition (à la Werner) is necessary and sufficient for the existence of an equilibrium with a continuum of traders and a finite number of assets. As in Aumann (1966), Hildenbrand (1974) and Schmeidler (1969), preferences are not assumed to be convex. We do not use Fatou's Lemma and do not assume that the consumption sets are compact. [source] Some conditions which make the constantly scaled H, control synthesis problems convexINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 1 2002Toru Asai Abstract In this paper, we present some computationally tractable conditions which make the constantly scaled H, control synthesis problem convex. If one of the conditions proposed in this paper holds, the constantly scaled H, control synthesis problem can be solved efficiently as an LMI problem. The results presented here include the existing results such as the state feedback and the full information problems as special cases. In addition, the results are generalized to the case that some of state variables are exactly available. Owing to this generalization, a larger class of problems can be reduced to convex problems, while reduced order controllers can be obtained. Copyright © 2001 John Wiley & Sons, Ltd. [source] Asymmetry in the detection of shapes from shading in infants,JAPANESE PSYCHOLOGICAL RESEARCH, Issue 3 2008TOMOKO IMURA Abstract:, We investigated 3- and 4-month-old infants' sensitivity to differences defined by shading using a paired-comparison familiarity/novelty preference procedure. Infants were familiarized with a pair of displays consisting of homogeneous shaded disks, and then were tested with two displays: the familiar display and a novel one containing shaded disks with reversed polarity (defined as the target). Experiment 1 examined two assumptions on discerning shapes from shading in infants by manipulating the orientations in the shading gradient of stimuli. When the orientation of the shading gradient was vertical, 4-month-old infants looked at the novel display for a longer time during the test trial. However, they failed to detect differences when the orientation of shading gradients was horizontal. Three-month-old infants did not detect differences in either orientation of the shading gradient. Experiment 2 examined asymmetry in the detection of convex versus concave shapes. Four-month-old infants failed to detect the target when the orientation of the shading grating was vertical and the target was convex. Taken with the results of Experiment 1, concave shapes were much easier to detect than convex shapes for 4-month-olds. This asymmetry suggests that 4-month-old infants process shading information in the same manner as adults. [source] The histological structure of the malleolar groove of the fibula in man: its direct bearing on the displacement of peroneal tendons and their surgical repairJOURNAL OF ANATOMY, Issue 2 2003T. Kumai Abstract The peroneal (fibularis) tendons are held in place within the malleolar groove by the superior peroneal retinaculum. If this is torn, the tendons can subluxate or dislocate. Understanding the anatomy of the region is important for treating these injuries when it becomes necessary to reconstruct the malleolar groove surgically. Serial transverse sections of the groove were cut from 10 dissecting room cadavers after routine histology processing. The structure of the malleolar groove differed significantly in its proximal and distal parts. Distally, the bone is convex and the shape of the groove is determined by a thick periosteal cushion of fibrocartilage that covers the bone surface. Proximally, the groove shape is determined by the bone itself, and the periosteum is thin and fibrous. The restriction of a periosteal fibrocartilage to the distal end suggests that it serves to adapt the shape of the malleolar groove to that of the tendons within it and thus promotes stress dissipation. Paradoxically, however, it increases the risk of damage to subluxated tendons, because these can be sliced longitudinally by a sharp ridge created from periosteal fibrocartilage when the retinaculum is torn. Our results suggest that if bone-block surgical procedures are used to reconstruct the malleolar groove, they are best restricted to its proximal part. [source] Having your water and drinking it too: resource limitation modifies density regulationJOURNAL OF ANIMAL ECOLOGY, Issue 1 2008COREY J. A. BRADSHAW Determining the interaction between extrinsic and intrinsic drivers of variation in population abundance through time continues to challenge ecologists. Chamaillé-Jammes and colleagues (this issue) examined African elephant time series to explore how water availability alters the density feedback mechanisms restricting population growth. The relationship between population growth rate and density shifted from an upward convex to a more linear form after controlling for rainfall. Spatial variation in water availability also attenuated density dependence as elephants adjusted their distribution relative to current environmental conditions. This work has important climate change implications for the conservation management of African herbivores. [source] Magnebike: A magnetic wheeled robot with high mobility for inspecting complex-shaped structuresJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 5 2009Fabien Tâche This paper describes the Magnebike robot, a compact robot with two magnetic wheels in a motorbike arrangement, which is intended for inspecting the inner casing of ferromagnetic pipes with complex-shaped structures. The locomotion concept is based on an adapted magnetic wheel unit integrating two lateral lever arms. These arms allow for slight lifting off the wheel in order to locally decrease the magnetic attraction force when passing concave edges, as well as laterally stabilizing the wheel unit. The robot has the main advantage of being compact (180 × 130 × 220 mm) and mechanically simple: it features only five active degrees of freedom (two driven wheels each equipped with an active lifter stabilizer and one steering unit). The paper presents in detail design and implementation issues that are specific to magnetic wheeled robots. Low-level control functionalities are addressed because they are necessary to control the active system. The paper also focuses on characterizing and analyzing the implemented robot. The high mobility is shown through experimental results: the robot not only can climb vertical walls and follow circumferential paths inside pipe structures but it is also able to pass complex combinations of 90-deg convex and concave ferromagnetic obstacles with almost any inclination regarding gravity. It requires only limited space to maneuver because turning on the spot around the rear wheel is possible. This high mobility enables the robot to access any location in the specified environment. Finally the paper analyzes the maximum payload for different types of environment complexities because this is a key feature for climbing robots and provides a security factor about the risk of falling and slipping. © 2009 Wiley Periodicals, Inc. [source] Voluntary Contributions to Multiple Public ProjectsJOURNAL OF PUBLIC ECONOMIC THEORY, Issue 1 2003M. Koster The problem of financing a set of discrete public goods (facilities, projects) by private contributions is studied. The corresponding cooperative game, the realization game, is shown to be convex. For the noncooperative setting we study a realization scheme that induces a strategic game. This contribution game is shown to be a generalized ordinal potential game; a best,response in the contribution game implies a best response in a coordination game in which the payoff to all players is the utilitarian collective welfare function, i.e., the sum of the utility functions of the players. Strategy profiles maximizing utilitarian welfare are strong Nash equilibria of the contribution game. Each strong Nash equilibrium corresponds in a natural way with a core element of the realization game, and vice versa. Moreover, each strong Nash equilibrium is coalitional proof. [source] Variation in tree growth, mortality and recruitment among topographic positions in a warm temperate forestJOURNAL OF VEGETATION SCIENCE, Issue 3 2006Riyou Tsujino Abstract: Questions: Do the population dynamics of trees differ among topographic positions and, if so, how does topographic position affect the population dynamics of species that are distributed in a topography-specific manner? Which is the most important life stage in determining vegetation patterns? Location: Primary and secondary warm temperate evergreen broad-leaved forest (40 - 280 m a.s.l.) on the western part of Yakushima Island, Japan. Methods: Mortality, recruitment, DBH growth and distribution of stems (= 5 cm DBH) in a 2.62-ha plot were surveyed in 1992 and 2002 to determine the relationships between population parameters and (1) topography and (2) distribution patterns of 17 common tree species. Results: Common species (n = 17) were classified into three distribution pattern groups: group A, distributed mainly on convex slopes; group B, on concave slopes, and group C, not aggregated with respect to topographic position. Stem mortality, recruitment and DBH growth were greater in group A than in group B within each topographic class. The hierarchy of stem mortality among topographic classes for groups A and B was convex > planar > concave. Stem recruitment density was relatively high on the convex and concave slopes, respectively, for groups A and B. Conclusions The topographical positions of adult trees were not always most suited for adult survival and growth. For group A, the distribution pattern of adults was determined in the juvenile stage, while this was not the case for group B. Studies of juvenile stages are important for understanding the demographic basis of vegetation distribution patterns. [source] RISK MEASURES ON ORLICZ HEARTSMATHEMATICAL FINANCE, Issue 2 2009Patrick Cheridito Coherent, convex, and monetary risk measures were introduced in a setup where uncertain outcomes are modeled by bounded random variables. In this paper, we study such risk measures on Orlicz hearts. This includes coherent, convex, and monetary risk measures on Lp -spaces for 1 ,p < , and covers a wide range of interesting examples. Moreover, it allows for an elegant duality theory. We prove that every coherent or convex monetary risk measure on an Orlicz heart which is real-valued on a set with non-empty algebraic interior is real-valued on the whole space and admits a robust representation as maximal penalized expectation with respect to different probability measures. We also show that penalty functions of such risk measures have to satisfy a certain growth condition and that our risk measures are Luxemburg-norm Lipschitz-continuous in the coherent case and locally Luxemburg-norm Lipschitz-continuous in the convex monetary case. In the second part of the paper we investigate cash-additive hulls of transformed Luxemburg-norms and expected transformed losses. They provide two general classes of coherent and convex monetary risk measures that include many of the currently known examples as special cases. Explicit formulas for their robust representations and the maximizing probability measures are given. [source] PROPERTIES OF OPTION PRICES IN MODELS WITH JUMPSMATHEMATICAL FINANCE, Issue 3 2007Erik Ekström We study convexity and monotonicity properties of option prices in a model with jumps using the fact that these prices satisfy certain parabolic integro,differential equations. Conditions are provided under which preservation of convexity holds, i.e., under which the value, calculated under a chosen martingale measure, of an option with a convex contract function is convex as a function of the underlying stock price. The preservation of convexity is then used to derive monotonicity properties of the option value with respect to the different parameters of the model, such as the volatility, the jump size, and the jump intensity. [source] Pareto Equilibria with coherent measures of riskMATHEMATICAL FINANCE, Issue 2 2004David Heath In this paper, we provide a definition of Pareto equilibrium in terms of risk measures, and present necessary and sufficient conditions for equilibrium in a market with finitely many traders (whom we call "banks") who trade with each other in a financial market. Each bank has a preference relation on random payoffs which is monotonic, complete, transitive, convex, and continuous; we show that this, together with the current position of the bank, leads to a family of valuation measures for the bank. We show that a market is in Pareto equilibrium if and only if there exists a (possibly signed) measure that, for each bank, agrees with a positive convex combination of all valuation measures used by that bank on securities traded by that bank. [source] Linear functionals on nonlinear spaces and applications to problems from viscoplasticity theoryMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 7 2008Waldemar Pompe Abstract A classical result in the theory of monotone operators states that if C is a reflexive Banach space, and an operator A: C,C* is monotone, semicontinuous and coercive, then A is surjective. In this paper, we define the ,dual space' C* of a convex, usually not linear, subset C of some Banach space X (in general, we will have C*,X*) and prove an analogous result. Then, we give an application to problems from viscoplasticity theory, where the natural space to look for solutions is not linear. Copyright © 2007 John Wiley & Sons, Ltd. [source] Starlike and convex rational mappings on infinite dimensional domainsMATHEMATISCHE NACHRICHTEN, Issue 2 2009Cho-Ho Chu Abstract We give starlike criteria for a class of rational mappings on the open unit ball of a complex Banach space. We also give a sufficient condition for these mappings to be convex when they are defined in Hilbert spaces. These criteria facilitate the construction of concrete examples of starlike and convex mappings on infinite dimensional domains (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Notes on the geometry of the space of polynomialsMATHEMATISCHE NACHRICHTEN, Issue 16 2007Han Ju Lee Abstract We show that the symmetric injective tensor product space is not complex strictly convex if E is a complex Banach space of dim E , 2 and if n , 2 holds. It is also reproved that ,, is finitely represented in if E is infinite-dimensional and if n , 2 holds, which was proved in the other way in [3]. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Convexity in x of the level sets of the first Dirichlet eigenfunctionMATHEMATISCHE NACHRICHTEN, Issue 13-14 2007Chie-Ping ChuArticle first published online: 7 SEP 200 Abstract On a planar domain which is convex in x, the level sets of the first Dirichlet eigenfunction for Laplacian are also convex in x. This gives an affirmative answer to a conjecture proposed by B. Kawohl. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||||||||||||||||||||