Uniform Growth Conditions Research Articles

Automatic transversality in contact homology I: regularity

This paper helps to clarify the status of cylindrical contact homology, a conjectured contact invariant introduced by Eliashberg, Givental, and Hofer in 2000. We explain how heuristic arguments fail to yield a well-defined homological invariant in the presence of multiply covered curves. We then introduce a large subclass of dynamically convex contact forms in dimension 3, termed dynamically separated, and demonstrate automatic transversality holds, thereby allowing us to define the desired chain complex. The Reeb orbits of dynamically separated contact forms satisfy a uniform growth condition on their Conley–Zehnder index under iteration, typically up to large action; see Definition 1.15. These contact forms arise naturally as perturbations of Morse–Bott contact forms such as those associated to $$S^1$$ -bundles. In subsequent work, we give a direct proof of invariance for this subclass and, when further proportionality holds between the index and action, powerful geometric computations in a wide variety of examples.

Growth conditions for uniform asymptotic stability of damped oscillators

The present paper is devoted to an investigation on the uniform asymptotic stability for the linear differential equation with a damping term, x″+h(t)x′+ω2x=0 and its generalization (ϕp(x′))′+h(t)ϕp(x′)+ωpϕp(x)=0, where ω>0 and ϕp(z)=|z|p−2z with p>1. Sufficient conditions are obtained for the equilibrium (x,x′)=(0,0) to be uniformly asymptotically stable under the assumption that the damping coefficient h(t) is integrally positive. The obtained condition for the damped linear differential equation is given by the form of a certain uniform growth condition on h(t). Another representation which is equivalent to this uniform growth condition is also given. Our results assert that the equilibrium can be uniformly asymptotically stable even if h(t) is unbounded. An example is attached to show this fact. In addition, easy-to-use conditions are given to guarantee that the uniform growth condition is satisfied. Moreover, a sufficient condition expressed by an infinite series is presented. The relation between the representation of an infinite series and the uniform growth condition is also clarified. Finally, our results are extended to be able to apply to the above-mentioned nonlinear differential equation.

On the [formula omitted] spectrum of Laplacians on graphs

We study the p-independence of spectra of Laplace operators on graphs arising from regular Dirichlet forms on discrete spaces. Here, a sufficient criterion is given solely by a uniform subexponential growth condition. Moreover, under a mild assumption on the measure we show a one-sided spectral inclusion without any further assumptions. We study applications to normalized Laplacians including symmetries of the spectrum and a characterization for positivity of the Cheeger constant. Furthermore, we consider Laplacians on planar tessellations for which we relate the spectral p-independence to assumptions on the curvature.

Simulation of heat transfer and convection during sapphire crystal growth in a modified heat exchanger method

Quasi-steady-state (QSS) and transient models, developed using the CrysMAS code, are employed to study the effects of transport mechanisms and cold finger design on the temperature distribution, melt flow field, and melt–crystal interface shape during the crystal growth of sapphire by a small-scale, modified heat exchanger method (HEM). QSS computations show the importance and effects of various heat transfer mechanisms in the crystal and melt, including conduction, internal radiation, and melt convection driven by buoyant and Marangoni forces. The design of the cold finger is demonstrated to have significant effects on growth states. Notably, transient computations on an idealized heat transfer model, supplemented with QSS calculations of a model with rigorous heat transfer representation, show that non-uniform growth conditions arise under uniform cooling of the system via a linear decrease in furnace set points. We suggest that more uniform HEM growth conditions may be achieved by using non-linear cool-down strategies.

Taguchi Method Optimization of Parameters for Growth of Nano Dimensional SiC Wires by Chemical Vapor Deposition Technique

SiC wires of different morphology were grown using methyltrichlorosilane (MTS) and hydrogen by chemical vapor deposition under ambient pressure. Taguchi method has been used to design experiments to get the optimum parameters for growing SiC wires of diameter in nanometer range. Results from XRD and SEM analyses showed the growth of β-SiC wires having different morphology. At higher temperature (1500 °C), the growth of SiC grains was observed rather than wires. The optimum deposition conditions for uniform diameter growth of SiC nano wires, smoothness of the surface and homogeneous growth of SiC on the surface have been obtained. The hydrogen to MTS flow rate ratio should be above 20 for the growth of SiC wires of nanometer diameter. The deposition temperature for the growth of crystalline SiC wires should be 1100-1300 °C. The total flow rate of carrier gas comprising of argon and hydrogen for a particular H2/MTS flow rate ratio is critical for morphological outcome of SiC. In the present study it was 2 lpm for H2/MTS flow rate ratio 14 to obtain wire morphology. When the total gas flow rate was increased to 6 lpm for the same H2/MTS flow rate ratio 14, the wire morphology of SiC disappeared and the formation of grains occurred. The optimum deposition temperature i.e. 1300 °C was kept constant and further experiments were conducted by changing H2/MTS mole ratio to verify morphological outcome of SiC. A plausible mechanism has been suggested for the above observations using vapor-solid mechanism.

Vertical gradient in soil temperature stimulates development and increases biomass accumulation in barley

We have detailed knowledge from controlled environment studies on the influence of root temperature on plant performance, growth and morphology. However, in all studies root temperature was kept spatially uniform, which motivated us to test whether a vertical gradient in soil temperature affected development and biomass production. Roots of barley seedlings were exposed to three uniform temperature treatments (10, 15 or 20°C) or to a vertical gradient (20-10°C from top to bottom). Substantial differences in plant performance, biomass production and root architecture occurred in the 30-day-old plants. Shoot and root biomass of plants exposed to vertical temperature gradient increased by 144 respectively, 297%, compared with plants grown at uniform root temperature of 20°C. Additionally the root system was concentrated in the upper 10cm of the soil substrate (98% of total root biomass) in contrast to plants grown at uniform soil temperature of 20°C (86% of total root biomass). N and C concentrations in plant roots grown in the gradient were significantly lower than under uniform growth conditions. These results are important for the transferability of 'normal' greenhouse experiments where generally soil temperature is not controlled or monitored and open a new path to better understand and experimentally assess root-shoot interactions.

GeOx and SiOx nanowires grown via the active oxidation of Ge and Si substrates

Abstract

Evaluation of Resistance to Sheath Blight ( Rhizoctonia solani) in Partial Indica Hybrid Rice Combinations from Southern China

Resistance to sheath blight is generally controlled by polygenes in rice ( Oryza sativa L.) and varies greatly among cultivars. At present, very few germplasms can be used as resistant parents in rice breeding. A total of 166 indica hybrid rice combinations collected from 11 provinces in southern China were evaluated for the resistance to sheath blight at seedling stage using artificial inoculation method. According the disease indexes (DIs) to 5 isolates of Rhizoctonia solani, the 166 hybrid combinations were classified into 5 types based on dynamic clustering analysis (DCA), with the ratios of 1.2% for resistance (R), 13.9% for moderate resistance (MR), 36.1% for moderate susceptibility (MS), 43.4% for susceptibility (S), and 5.4% for high susceptibility (HS); but no combination was immune or highly resistant to the disease. K-you 88 and Zhongyou 9801 showed relatively high resistance at seedling stage, but their adult resistance should be further evaluated. The discriminant function for each resistance type was calculated using Bayes method, and the accuracy rate for discrimination was 96.39%. The average DI ranged from 2.84 to 7.64 with an average of 5.27. The concept of synthetic disease index (SDI) was also introduced to classify the 166 hybrid combinations, which is the overall resistance performance to total isolates tested. Based on SDI grading criteria, the 166 hybrid combinations were also divided into R, MR, MS, S, and HS types with the ratios of 1.2%, 13.3%, 63.3%, 21.7%, and 0.6%, respectively. The SDI classification system was significantly correlated with the DCA system ( r = 0.81, P < 0.01), showing that both methods can be used for evaluating the disease resistance. The DCA method is suitable for seedling screening under the uniform growth condition. The SDI method is independent on test time, place, and batch, and thus can be applied in relatively complicated conditions. Twenty-six combinations were identified as resistant (R or MR) indica hybrid rice using both methods. The genetic distances among these combinations ranged from 0.04 to 0.71. Twenty-two of them were grouped in the same clade after cluster analysis using unweighted pair group method with arithmetic mean (UPGMA) method. This result and pedigree analysis showed a narrow genetic background of the resistant hybrid combinations.

Gene position within a long transcript as a determinant for stochastic switching in bacteria

How cultures of genetically identical cells bifurcate into distinct phenotypic subpopulations under uniform growth conditions is an important question in developmental biology of relevance even to relatively simple developmental systems, such as spore formation in bacteria. A growing Bacillus subtilis culture consists of either cells that are motile and can swim or cells that are non-motile and are chained together. In this issue of Molecular Microbiology, Cozy and Kearns show that the probability of a cell to become motile depends on the position of the sigD gene within the long (27 kb) motility operon. sigD encodes the alternative sigma factor sigma(D) that, together with RNA polymerase, drives expression of genes required for cell separation and the assembly of flagella. sigD is the penultimate gene of the B. subtilis motility operon and, in the control strain approximately, 70% of the cells are motile. When sigD was moved upstream within the operon, a larger fraction of cells became motile (up to 100%). This study highlights that the position of a gene within an operon can have a large impact on the control of gene expression. Furthermore, it suggests that RNA polymerase processivity or mRNA turnover can play important roles as sources of noise in bacterial development, and that gene position might be an unrecognized and possibly widespread mechanism to regulate phenotypic variation.

Correlated changes in thermotolerance traits and body color phenotypes in montane populations of Drosophila melanogaster : analysis of within‐ and between‐population variations

Thermotolerance traits vary across geographical gradients but there is a lack of clinal variation in some Drosophila species. Thus, it is not clear whether thermotolerance or other correlated traits are the target of natural selection. In order to test selection responses, we investigated body melanization and thermotolerance traits in six altitudinal populations of Drosophila melanogaster. Based on rearing different geographical populations under uniform growth conditions at 21 °C (common garden experiments), clinal variations for cold resistance are in the direction opposite to heat resistance along an altitudinal gradient, that is darker flies from highland populations evidenced higher levels of cold resistance while lowland populations showed higher heat resistance. Phenotypic plastic responses for body melanization at 17–28 °C showed significant correlations with thermotolerance traits. At 17 °C, regression coefficients as a function of altitude are highly significant and positive for cold resistance but negative for heat knockdown. However, for flies reared at 28 °C, there is no elevational change in melanization as well as thermotolerance traits. Thus, both genetic and plastic changes of body melanization and thermotolerance traits suggest a correlated selection response. Further, within-population analyses of body melanization (based on dark, intermediate and light color phenotypes) showed significant associations with thermotolerance traits. Correlated variations in body melanization and thermal tolerances are associated with climatic thermal variability (Tcv) but not with Tmin. or Tmax. along an altitudinal gradient.

The equivalence between uniqueness and continuous dependence of solutions for FBSDEs with continuous monotone coefficients

In this paper we study one kind of coupled forward–backward stochastic differential equation. With some particular choice for the coefficients, if one of them satisfies a uniform growth condition and they are accordingly monotone, then we obtain the equivalence between the uniqueness of solution and its continuous dependence on x and ξ , where x is the initial value of the forward component and ξ is the terminal value of the backward component.

Electrochemical preparation and structural characterization of platinum thin film on a polypyrrole film modified ITO electrode

Platinum nanostructures have been fabricated by electrochemical deposition of platinum onto indium tin oxide (ITO) glass substrate modified with thin polypyrrole film. The crystal size and the number density of the platinum nanoparticles have been examined by varying several deposition parameters, including the thickness of the PPy film and the current densities for platinum deposition. Optimal conditions for uniform growth of nanoparticles well-dispersed on the ITO have been determined, along with insight into the mechanism of crystal growth. The PPy film thickness principally affect the size and number density of the nanoparticles, while the platinum deposition current densities could be used to regulate the shape of the nanoparticles. In addition, the flower-like platinum nanoparticles showed high catalytic activity on electrochemical oxidation of methanol, and its activity was measured to be approximately 1.9 times that of bare platinum.

Simultaneous detection of ascorbic acid, uric acid and homovanillic acid at copper modified electrode

The copper was deposited on glassy carbon (GC) and indium tin oxide (ITO) electrodes by electrochemical method. The copper structures on electrode were characterized by atomic force microscope, X-ray diffractometeric pattern and differential pulse voltammetric studies. Optimal conditions for uniform growth of copper structures on the electrode were established. Voltammetric sensor was fabricated using the copper deposited GC electrode for the simultaneous detection and determination of uric acid (UA) and homovanillic acid (HVA) in the presence of excess concentrations of ascorbic acid (AA). The voltammetric signals due to AA and UA oxidation were well separated with a potential difference of 400 mV and AA did not interfere with the measurement of UA and HVA at the GC/Cu electrode. Linear calibration curves were obtained in the concentration range 1–40 μM for AA and 20–50 μM for UA at physiological pH and a detection limit of 10 nM of UA in the presence of 10-fold excess concentrations of AA was achieved. The simultaneous detection of submicromolar concentrations of AA, UA and HVA was achieved at the GC/Cu electrode. The practical utility of the present GC/Cu modified electrode was demonstrated by measuring the AA content in Vitamin C tablet, UA content in human urine and blood serum samples with satisfactory results.

Existence of the solutions of backward–forward SDE's with continuous monotone coefficients

We seek an alternative approach to produce the solution of a certain class of BFSDE's without employing the classical time restriction. In the literature there are various results about this problem, none of them implying the other. The previous methods always assume to have globally Lipschitz coefficients. Here, under some particular choices for the coefficients, we show that if one of them satisfies a uniform growth condition and they are accordingly monotone, one can find a solution (not necessarily unique), without even resorting to the Lipschitz property. Finally we provide some examples to show this is a new class of equations.

On Borel’s Regularization Theorem

Introduction. Let G be a non compact semi simpel real Lie group with finite center and finitely many connected components. Assume that Γ ⊂ G is an arithmetic subgroup such that Γ\G is non compact. If M is a finite dimensional representation of G, then Borel proves that there are natural isomorphisms H(Γ,M) −→ Hj(Ω∗(X, M)umg) for all j, see [B 1, B 2, B 3, B 4]. Here Hj(Γ,M) is the group cohomology of Γ acting on M and Ω∗(X, M)umg is the complex of smooth M–valued Γ– invariant differential forms of uniform moderate growth on the symmetric space X attached to G. For the definition of growth conditions, see 1.1 and 2.4. The main result of this paper, theorem 3.2, says that the above isomorphy holds if Γ is any discrete subgroup of a reductive Lie group G with finitely many connected components. Moreover M can be any smooth representation of G on a Frechet space. Borel uses in his proof the Borel–Serre compactification of Γ\X and a tricky spectral–sequence argument to go from moderate growth conditions to uniform moderate growth conditions. In this paper we work essentially only on the symmetric space X. Here the uniform moderate growth conditions for the inverse map log of the exponential map exp p ∼ −→ X are most important, see 2.2 and 2.3. They are used to prove a global version of Poincare’s lemma with growth conditions on X, see 2.4. There are other contributions to Borel’s regularization theorem. J. Franke gives a different proof of Borel’s result in the adelic context for reductive algebraic groups, see [F]. U. Bunke and M. Olbrich give an extension of the first version of Borel’s result with moderate instead of uniform moderate growth conditions on Ω∗(X, M) to infinite dimensional coefficients M of moderate growth. Their result also holds for certain non arithmetic subgroups Γ of G, see [B–O].

Intraspecific Diversity and Morpho-Phenological Variation in Phaseolus lunatus L. from the Yucatan Peninsula, Mexico

The genetic diversity of P. lunatus in the Yucatan Peninsula was assessed on the basis of its morphological and phenological characters. Our results were then discussed in relation to ethnobotanic information obtained about the intraspecific diversity recognized by farmers, their selection criteria, agronomic management, production purpose and percentage of cultivated area. Research was undertaken in one of the cultural subareas of Mesoamerica, the Lowland Maya area, where traditional agriculture has been more persistent and where high diversity of P. lunatus landraces has been recorded. Four of the 13 cultural-geographic zones established for the origin of this culture were included, 160 farmers from 12 localities were interviewed, and 149 seed samples of P. lunatus germplasm were collected and analyzed using six characters. A subset of these samples was grown under ex situ uniform growth conditions and analyzed using 28 characters. Ethnobotanical and morpho-phenological data indicated 30 putative distinct landraces, two wild, and two weedy variants, suggesting gene flow among them. Richness and diversity estimates were greatest, and evenness lowest, where there was: 1) minimal agricultural intensification, 2) wild and weedy populations, and 3) greater persistence of traditional culture. Results underscored the importance of establishing in situ conservation programs in these areas.

High variability of primary production in oligotrophic waters of the Atlantic Ocean: uncoupling from phytoplankton biomass and size structure

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 257:1-11 (2003) - doi:10.3354/meps257001 High variability of primary production in oligotrophic waters of the Atlantic Ocean: uncoupling from phytoplankton biomass and size structure Emilio Marañón1,*, Michael J. Behrenfeld2, Natalia González3, Beatriz Mouriño1, Mikhail V. Zubkov4 1Departamento de Ecología y Biología Animal, Facultad de Ciencias, Universidad de Vigo, 36200 Vigo, Spain 2National Aeronautics and Space Administration, Goddard Space Flight Center, Code 971, Building 33, Greenbelt, Maryland 20771, USA 3Departamento de Matemáticas, Física Aplicada y Ciencias de la Naturaleza, Universidad Rey Juan Carlos, 28933 Móstoles, Madrid, Spain 4George Deacon Division for Ocean Processes, Southampton Oceanography Centre, University of Southampton, Southampton SO14 3ZH, United Kingdom *Email: em@uvigo.es ABSTRACT: The oligotrophic waters of the Subtropical Gyres cover >60% of the total ocean surface and contribute >30% of the global marine carbon fixation. Despite apparently uniform growth conditions over broad areas, primary production in these regions exhibits a remarkable degree of variability. In this study of 34 stations in the North and South Atlantic Subtropical Gyres, we found a 20 fold variation (from 18 to 362 mgC m-2 d-1) in water-column-integrated primary production rate (∨PP), while chlorophyll biomass only varied by a factor of 3. The changes in productivity were not associated with variations in incident surface irradiance, chlorophyll concentration, phytoplankton C biomass or phytoplankton size structure. The rate of nutrient supply to the euphotic layer, as estimated from variations in the depth of nitracline, appeared as the most relevant environmental factor in explaining the observed variability in ∨PP. We found significant changes in the composition of the picophytoplankton community across the range of measured productivities. The relative biomass contribution of Synechococcus spp. and the picoeukaryotes tended to increase with increasing ∨PP, whereas the opposite was true for Prochlorococcus spp. Across the wide range of measured primary productivity rates, the persistent dominance of picophytoplankton indicates that the microbial loop and the microbial food web continued to be the most important trophic pathways. Our observations of the oligotrophic ocean reflect a dynamic ecosystem where the microbial community responds to environmental forcing with significant changes in biological rates rather than trophic organization. KEY WORDS: Primary production · Chlorophyll · Picoplankton · Size structure · Subtropical Gyres · Atlantic Ocean Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 257. Online publication date: August 07, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Inbreeding depression in a rare plant, Scabiosa canescens (Dipsacaceae).

Plants from a population of Scabiosa canescens, a locally rare species with a narrow ecological amplitude, were raised under uniform growth conditions to examine the phenotypic effects of one generation selfing and outcrossing. Particular attention was given to direct components of fitness (seedling biomass, rosette leaf number, head number, flower number per head), but two morphological characters (plant height, flower size) were also considered. Estimates of inbreeding depression (delta), adjusted for maternal effects and lack of balance, were compared and tested for significance using randomization and boostrap procedures. Inbreeding significantly depressed several characters during both early and late stages of the life cycle, with delta ranging from 0.14 (flower size) to 0.37 (seedling biomass). Based on these and other results, we propose that S. canescens is susceptible to inbreeding and that the genetic basis of inbreeding depression varies across life stages.

The effect of inbreeding on fluctuating asymmetry in Scabiosa canescens (Dipsacaceae)

Developmental instability and fluctuating asymmetry (FA) describe the inability of organisms to correct for random accidents under development and has become a major but controversial topic in evolutionary biology. Theoretical models predict that the level of FA should increase as a result of inbreeding, but empirical results are ambiguous. Moreover, the relationship between fitness and FA is still debated. In the current study, plants from a population of Scabiosa canescens, a locally rare species in southern Sweden, were raised under uniform growth conditions to examine the effects of one-generation of selfing and outcrossing on FA in flower morphology. The level of flower FA was significantly higher (p = 0.038) for inbred progeny than for offspring derived from outcross pollinations. Given that earlier studies of this species have found no negative relation between heterozygosity and FA, the results support the conclusion that expression of deleterious recessive alleles are responsible for the increase of FA. There was no correlation between FA and estimates of five fitness-related traits when estimated at the individual level. However, a companion study found significant inbreeding depression for all fitness traits, and a negative association between FA and fitness could therefore be asserted at the treatment level (inbred/outbred progeny). Hence, FA seems to be useful to predict inbreeding depression in S. canescens, but specific individuals with high fitness cannot be identified based on their FA levels.

Formulas relating [formula omitted] stability estimates of discrete-time and sampled-data nonlinear systems

We provide an explicit KL stability or input-to-state stability (ISS) estimate for a sampled-data nonlinear system in terms of the KL estimate for the corresponding discrete-time system and a K function describing inter-sample growth. It is quite obvious that a uniform inter-sample growth condition, plus an ISS property for the exact discrete-time model of a closed-loop system, implies uniform ISS of the sampled-data nonlinear system. Our results serve to quantify these facts by means of comparison functions. Our results can be used as an alternative to prove and extend results in [1] or extend some results in [4] to a class of nonlinear systems. Finally, the formulas we establish can be used as a tool for some other problems which we indicate.