408 research outputs found

    The in vitro manipulation of cauliflower (Brassica oleracea L. convar. botrytis (L.) Alef. var. botrytis L.) meristematic tissues for utilisation in genetic improvement programmes

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    Merged with duplicate record 10026.1/629 on 27.02.2017 by CS (TIS)Cauliflower curd meristem activity (organogenic, plastochronic, phyllotactic) was analysed biometrically and confirmed that the curd is the product of a constant process of meristem production and branch ramification with little if any dominance between branch apices. A growth model based on curd branching pattern was developed and its mathematical expression enabled the estimation of the number of meristems carried by a curd at maturity to be over ten million which was previously widely underestimated. Analysis of the response to the in vitro culture of this meristematic tissues revealed that meristems are not predetermined to produce flower and that their shoot regeneration capacity is under several levels of control, the most important being explant physical property (size) and the culture system (nutrient supply). Optimisation of these parameters enabled the development of a low cost, semi-automated protocol for mass production of cauliflower propagules at an unprecedented scale with over 10000 propagules produced per curd. Micropropagules a few millimetres in length were produced, encapsulated in calcium alginate hydrogel, stored at 4°C for several months and used as an 'artificial seed' system of cauliflower propagation. The response to the procedure of micropropagule production is genotype-dependent with summer heading varieties being less reactive than winter heading varieties, this phenomenon was also associated with plasmalemma instability at the cellular (protoplast) level. Furthermore, this material was successfully cryopreserved in liquid nitrogen using a dehydration I vitrification method. The micropropagation protocol is of great interest when used as a regeneration system for experiments involving genetic manipulation such as genetic transformation. A preliminary study of genetic transformation by microprojectile bombardment, using the gus reporter gene, allowed transient expression in curd meristematic tissue. The fundamental and industrial implications for cauliflower breeding of the different protocols developed in this thesis are discussed

    Bayesian optimization to enhance coverage performance of a swarm of UAV with chaotic dynamics

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    We introduce the optimization of CACOC through Bayesian Optimization. CACOC is based on a chaotic system, i.e. Rossler system whose behavior can be modified by tuning the α parameter. In order to evaluate the performance of CACOC for different value of α, the coverage metric has to be evaluated after simulation. The latter is time-consuming. Therefore, a surrogate-based optimization, i.e. Bayesian Optimization has been privilegied to tackle this issue. An analysis of the chaotic system with the obtained α value has been performed to compare the periodic orbits and their associated patterns. Numerical results show that the best α value avoid a waste of time in periodic region of the bifurcation diagram. Future works will focus on more complex chaotic system as well as new application domain of the optimized CACOC approach

    The Rover Environmental Monitoring Station Ground Temperature Sensor: A Pyrometer for Measuring Ground Temperature on Mars

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    We describe the parameters that drive the design and modeling of the Rover Environmental Monitoring Station (REMS) Ground Temperature Sensor (GTS), an instrument aboard NASA’s Mars Science Laboratory, and report preliminary test results. REMS GTS is a lightweight, low-power, and low cost pyrometer for measuring the Martian surface kinematic temperature. The sensor’s main feature is its innovative design, based on a simple mechanical structure with no moving parts. It includes an in-flight calibration system that permits sensor recalibration when sensor sensitivity has been degraded by deposition of dust over the optics. This paper provides the first results of a GTS engineering model working in a Martian-like, extreme environment

    Complex lithium ion dynamics in simulated LiPO3 glass studied by means of multi-time correlation functions

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    Molecular dynamics simulations are performed to study the lithium jumps in LiPO3 glass. In particular, we calculate higher-order correlation functions that probe the positions of single lithium ions at several times. Three-time correlation functions show that the non-exponential relaxation of the lithium ions results from both correlated back-and-forth jumps and the existence of dynamical heterogeneities, i.e., the presence of a broad distribution of jump rates. A quantitative analysis yields that the contribution of the dynamical heterogeneities to the non-exponential depopulation of the lithium sites increases upon cooling. Further, correlated back-and-forth jumps between neighboring sites are observed for the fast ions of the distribution, but not for the slow ions and, hence, the back-jump probability depends on the dynamical state. Four-time correlation functions indicate that an exchange between fast and slow ions takes place on the timescale of the jumps themselves, i.e., the dynamical heterogeneities are short-lived. Hence, sites featuring fast and slow lithium dynamics, respectively, are intimately mixed. In addition, a backward correlation beyond the first neighbor shell for highly mobile ions and the presence of long-range dynamical heterogeneities suggest that fast ion migration occurs along preferential pathways in the glassy matrix. In the melt, we find no evidence for correlated back-and-forth motions and dynamical heterogeneities on the length scale of the next-neighbor distance.Comment: 12 pages, 13 figure

    Auxin controls gravitropic setpoint angle in higher plant lateral branches.

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    Lateral branches in higher plants are often maintained at specific angles with respect to gravity, a quantity known as the gravitropic setpoint angle (GSA) [1]. Despite the importance of GSA control as a fundamental determinant of plant form, the mechanisms underlying gravity-dependent angled growth are not known. Here we address the central questions of how stable isotropic growth of a branch at a nonvertical angle is maintained and of how the value of that angle is set. We show that nonvertical lateral root and shoot branches are distinguished from the primary axis by the existence of an auxin-dependent antigravitropic offset mechanism that operates in tension with gravitropic response to generate angled isotropic growth. Further, we show that the GSA of lateral roots and shoots is dependent upon the magnitude of the antigravitropic offset component. Finally, we show that auxin specifies GSA values dynamically throughout development by regulating the magnitude of the antigravitropic offset component via TIR1/AFB-Aux/IAA-ARF-dependent auxin signaling within the gravity-sensing cells of the root and shoot. The involvement of auxin in controlling GSA is yet another example of auxin's remarkable capacity to self-organize in development [2] and provides a conceptual framework for understanding the specification of GSA throughout nature

    The Outcome of the Axillofemoral Bypass: A Retrospective Analysis of 45 Patients

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    Purpose This study was designed to retrospectively analyze outcomes of axillofemoral bypass (AxFB) operations performed in patients with severe comorbidities. Methods All patients (n = 45) who received an AxFB between 1990 and 2005 for aortoiliac occlusive disease (AIOD, n = 35) or infectious aortic disease (IAD, n = 10) were included. Information on patency of the bypass and mortality was retrieved from patient records. A Kaplan-Meier survival analysis was performed to illustrate survival rates, limb salvage, and primary and secondary patency. Results Included patients had several comorbidities and a high operative risk. In this group, a 30-day mortality rate of 20% was found: 17% for the AIOD group, and 30% for the IAD group. During 5-year follow-up 20 patients died, of which 15 during the first year after operation. Survival rates were at 64 and 41% at 1 and 5 years and limb salvage rates were 84% for both these years. Primary patency rates at 1 and 5 years were 72 and 58%, respectively, and secondary patency rates were 86% at both time points. Conclusions High mortality rates were found in AIOD or IAD patients who received an AxFB. However, for high-risk patients with an already reduced life expectancy, the AxFB remains an alternative with acceptable patency rate