Cernes manquants et houppier vivant chez le pin laricio (Pinus nigra Arn. ssp. laricio (Poir.) Maire)

1998 ◽  
Vol 76 (12) ◽  
pp. 2051-2060
Author(s):  
Céline Meredieu ◽  
Yves Caraglio
Keyword(s):  
Cross Sections ◽  
Cambial Activity ◽  
Pinus Nigra ◽  
Point Of View ◽  
Lower Side ◽  
Growth Rings ◽  
Branch Growth ◽  
Crown Characteristics ◽  
Pinus Laricio ◽  
Tree Development

During a study on the live crown characteristics of Pinus laricio (Pinus nigra Arn. ssp. laricio (Poir.) Maire), the observation of branch cross-sections allowed us to work on the problem of the discontinuance of cambial activity. This work points out the existence of missing rings with a histologic point of view and establishes the generality of the phenomenon for this species. In addition to the observations at the base of living branches, the cross-sections in all the successive growth units of the branch were observed to establish the distribution of the annual wood layers along the branch and to ascertain the dissymmetry between the upper side and the lower side of the branch. The occurrence of this phenomenon in the upper part of the crown raises the problem of the contribution of these branches to tree development and its implication in forest management.Key words: growth rings, Pinus nigra Arn. ssp. laricio (Poir.) Maire, missing rings, anatomy, branch growth, crown.

Eccentric Deposition of Secondary Xylem in Stems of the Climber Ephedra Campylopoda (Gnetales)

IAWA Journal ◽  
1999 ◽  
Vol 20 (2) ◽  
pp. 165-170 ◽  
Author(s):  
Simcha Lev-Yadun
Keyword(s):  
Secondary Xylem ◽  
Cambial Activity ◽  
Lower Side ◽  
Growth Rings ◽  
Woody Climber

In Ephedra campylopoda, a woody climber of the Ephedraceae (Gnetales), the secondary xylem of the upper and lower sides of horizontal stems has the same structure. However, cambial activity in the lower side is greater, producing 1.5 times more xylem and 1.25 times more growth rings in thin stems and 1.8 times more xylem in thick stems. Gelatinous fibres are not formed in the upper side or elsewhere in the xylem. I suggest that this difference in cambial activity does not change the flexibility of the stems, an important adaptation for a climber.

scholarly journals GRIBOV PROBLEM FOR GAUGE THEORIES: A PEDAGOGICAL INTRODUCTION

2004 ◽  
Vol 01 (04) ◽  
pp. 423-441 ◽  
Author(s):  
GIAMPIERO ESPOSITO ◽  
DIEGO N. PELLICCIA ◽  
FRANCESCO ZACCARIA
Keyword(s):  
Cross Sections ◽  
Gauge Theories ◽  
Functional Integral ◽  
Point Of View ◽  
Spherically Symmetric ◽  
Abelian Gauge ◽  
Gauge Transformations ◽  
Recent Developments ◽  
Gribov Ambiguity ◽  
Gribov Copies

The functional-integral quantization of non-Abelian gauge theories is affected by the Gribov problem at non-perturbative level: the requirement of preserving the supplementary conditions under gauge transformations leads to a nonlinear differential equation, and the various solutions of such a nonlinear equation represent different gauge configurations known as Gribov copies. Their occurrence (lack of global cross-sections from the point of view of differential geometry) is called Gribov ambiguity, and is here presented within the framework of a global approach to quantum field theory. We first give a simple (standard) example for the SU(2) group and spherically symmetric potentials, then we discuss this phenomenon in general relativity, and recent developments, including lattice calculations.

Influence of Surface Condition on Oxides Layer Morphology on NiCrAlY Coating during Oxidation at Temperature 1000°C and 1100°C

2015 ◽  
Vol 227 ◽  
pp. 385-388 ◽  
Author(s):  
Grzegorz Moskal ◽  
Dawid Niemiec
Keyword(s):  
Cross Sections ◽  
Surface Characterization ◽  
Surface Condition ◽  
Point Of View ◽  
Inconel 625 ◽  
Oxidation Test ◽  
Nicraly Coating ◽  
Static Oxidation ◽  
Plasma Spraying Process

Characterization of top-surface of NiCrAlY coating deposited by plasma spraying process on Inconel 625 Ni based superalloys was analyzed in two different completely conditions. First of them was as sprayed state of NiCrAlY coating and the second one was condition after grinding process. The basic aim of this treatment was related to obtain totally different conditions of coatings surface especially from roughness point of view. Those two types of top surface morphology was a base to comparison of oxidation resistant during static oxidation test at temperature of 1000°C and 1100°C. The temperature of static oxidation test was 1000°C and 1100°C. The specimens were moved out from furnace after 25, 300, 500, 750 and 1000 hours of exposition in laboratory air. The range of investigations after each interval included top surface characterization of specimens by SEM, XRD and EDS method. Those investigations showed that different types of top surface conditions had a fundamental influence on oxides layer morphology. Especially in the case of phase`s constituent of oxides zone. More detailed investigations were made on the cross sections of two types of investigated specimens. Analysis of oxides layer morphology showed in this case basic differences in thickness of oxides zone which was much higher in the case of as sprayed NiCrAlY coating.

scholarly journals Spirals: their orientation and description

1994 ◽  
Vol 13 (1) ◽  
pp. 54-54
Author(s):  
Stefan A. Revets
Keyword(s):  
Cross Sections ◽  
Oxford English Dictionary ◽  
Circular Motion ◽  
Lower Side ◽  
Spiral Coil

Abstract. The trochoid coiling mode is the most dominant amongst hyaline foraminifera. The parallels in shape with especially gastropods neatly explains the use of the same terms to describe the spiral coiling. Other terms came in use, at first well-defined, but gradually losing their precision. Because of growing demands of systematics and changes in stress of use and value of characters, the inadequacy of this terminology has become a stumbling block. The terms ventral/dorsal and spiral/umbilical denote different things and are therefore all useful: the latter pair should not be relinquished as suggested (Haynes, 1990: 512). Historically, the terms ventral/dorsal and upper and lower side have been used by most students of the foraminifera with only few exceptions (notably Reuss and Loeblich & Tappan). Despite the protist nature of foraminifera, dorsal and ventral continued to be used, analogous to terms used to describe, for example gastropods. Far fewer problems beset the terms spiral and umbilical, which arc generally defined (Oxford English Dictionary) as: spiral a.. n. & v. 1. a. Coiled; winding about a centre in an enlarging or decreasing circular motion, either on a flat plane or rising in a cone. spire n. Spiral, coil; single twist of this; upper part of spiral shell [F. f. Lf. Gk speira coil] umbilical a. 1. Of, situated near, affecting, the umbilicus 2. Centrally placed. umbilicus n. Navel; (Bot. & Zool.) navel-like formation; (Geom.) point in a surface through which all cross-sections have same curvature [I., rel. to Gk omphalos]ORIENTATION: A GEOMETRICAL . . .

scholarly journals Electron-capture modes with realistic nuclear structure calculations

2019 ◽  
Vol 21 ◽  
pp. 4
Author(s):  
P. G. Giannaka ◽  
T. S. Kosmas
Keyword(s):  
Electron Capture ◽  
Cross Sections ◽  
Nuclear Reactions ◽  
Random Phase ◽  
Point Of View ◽  
Electron Neutrino ◽  
Β Decay ◽  
Decay Modes ◽  
Theory Point ◽  
Nuclear Structure Calculations

Nuclear electron capture posses prominent position among other weak interaction processes occuring in explosive nucleosynthesis. In particular, this process plays important role in the core-colapse of massive stars by modifying the electron to baryon ratio Ye. From a nuclear theory point of view, such processes may be studied by using the same nuclear methods (e.g. the quasi-particle random phase approximation, QRPA), employed in the present work with these used for the one-body charge changing nuclear reactions (β-decay modes, charged-current electron-neutrino absorption by nuclei, etc). In this work we calculate e−-capture cross sections on 56Fe using two different approaches. At first, original cross section calculations are perfored by using the pn-QRPA method considering all the accessible transitions of the final nucleus 56Mn. Secondly, we evaluate the Gamow-Teller strength distributions and obtain the cross sections at the limit of zero-momentum transfer. The agreement between the two methods is very good.

scholarly journals Influence of measuring force on CMM accuracy

2018 ◽  
Vol 208 ◽  
pp. 03004
Author(s):  
Bin Wang
Keyword(s):  
Cross Sections ◽  
Measurement Accuracy ◽  
Coordinate Measuring Machine ◽  
Point Of View ◽  
Signal Acquisition ◽  
Force Model ◽  
Thin Part ◽  
Measuring Machine ◽  
The Relationship ◽  
Measuring Force

The measuring accuracy of CMM (Coordinate Measuring Machine) is influenced by many factors, such as temperature, humidity, measuring force and method of signal acquisition. For thin parts, the influence of measuring force is especially obvious. In this paper, the relationship between measuring force and measurement accuracy is studied for a thin part with a U-shaped cross-section. By analyzing the structure of the probe and establishing the force model, the influencing factors of the accuracy of CMM are obtained, and the influence of the contact deformation and the bending deformation on the measurement accuracy is analyzed from the point of view of material mechanics. At the same time, the measurement accuracy of different measuring cross-sections is analyzed. Through the research of this paper, the relationship between measuring force and CMM is established, and an effective method to improve the accuracy of CMM is also found.

scholarly journals Radiocarbon Analysis Confirms the Annual Nature of Sagebrush Growth Rings

Radiocarbon ◽  
2007 ◽  
Vol 49 (3) ◽  
pp. 1231-1240 ◽  
Author(s):  
Franco Biondi ◽  
Scotty D J Strachan ◽  
Scott Mensing ◽  
Gianluca Piovesan
Keyword(s):  
Great Basin ◽  
Cross Sections ◽  
Environmental Changes ◽  
Spatially Explicit ◽  
Growth Rings ◽  
Ams Radiocarbon Dating ◽  
Big Sagebrush ◽  
Proxy Records ◽  
Annual Resolution ◽  
Wildfire Regimes

In the Great Basin of North America, big sagebrush (Artemisia tridentata Nutt.) growth rings can be used to reconstruct environmental changes with annual resolution in areas where there is otherwise little such information available. We tested the annual nature of big sagebrush wood layers using accelerator mass spectrometry (AMS) radiocarbon dating. Four cross-sections from 3 sagebrush plants were collected near Ely, Nevada, USA, and analyzed using dendrochronological methods. Ten 14C measurements were then used to trace the location of the 1963–64 “bomb spike.” Although the number of rings on each section did not exceed 60, crossdating was possible within a section and between sections. Years assigned to individual wood layers by means of crossdating aligned with their expected 14C values, matching the location of the 14C peak. This result confirmed the annual nature of growth rings formed by big sagebrush, and will facilitate the development of spatially explicit, well-replicated proxy records of environmental change, such as wildfire regimes, in Great Basin valleys.

Collapse study of thin-walled polygonal section columns subjected to oblique loads

2007 ◽  
Vol 221 (7) ◽  
pp. 801-810 ◽  
Author(s):  
P Hosseini-Tehrani ◽  
S Pirmohammad
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Rigid Wall ◽  
Point Of View ◽  
Explicit Finite Element ◽  
Thin Walled ◽  
Oblique Load ◽  
Crash Behaviour ◽  
Vehicle Crashworthiness ◽  
Load Conditions

The present paper deals with the collapse simulation of aluminium alloy extruded polygonal section columns subjected to oblique loads. Oblique load conditions in numerical simulations are applied by means of impacting a declined rigid wall on the tubes with no friction in this task. The explicit finite element code LS-DYNA is used to simulate the crash behaviour of polygonal section columns that are undergoing both axial and bending collapse situations. In order to validate LS-DYNA results the collapse procedure of square columns is successfully simulated and the obtained numerical results are compared with actual available experimental data. Mean crush loads and permanent displacements corresponding to load angles have been investigated, considering columns with square, hexagonal, octagonal, decagonal, and circular cross-sections. It is shown that the octagonal cross-section has better characteristics from the point of view of vehicle crashworthiness under oblique load conditions.

Seasonal cambial activity and wood formation in trees and lianas of Leguminosae growing in the Atlantic Forest: a comparative study

Botany ◽  
2015 ◽  
Vol 93 (4) ◽  
pp. 211-220 ◽  
Author(s):  
Arno Fritz das Neves Brandes ◽  
Claudio Sergio Lisi ◽  
Leonardo Davi S.A.B. da Silva ◽  
Kishore S. Rajput ◽  
Cláudia Franca Barros
Keyword(s):  
Tree Species ◽  
Secondary Xylem ◽  
Cambial Activity ◽  
Wood Formation ◽  
Montane Forest ◽  
Vascular Cambium ◽  
Growth Rings ◽  
Indirect Methods ◽  
Annual Growth Rings ◽  
Direct And Indirect Methods

Cambial activity and the formation of secondary xylem were investigated in the main stem of three arboreal leguminous species and one liana. To compare the seasonal vascular cambium behavior of these species, two methods were concurrently applied: induction of injury in the vascular cambium and anatomical analysis of the vascular cambium and adjacent zones (differentiation zone). One tree species, Pseudopiptadenia contorta (DC.) G.P.Lewis & M.P.Lima, was sampled in three forest formations: alluvial, submontane, and montane. Two more tree species, Apuleia leiocarpa (Vogel) J.F.Macbr. and Pseudopiptadenia leptostachya (Benth.) Rauschert, were sampled in submontane and montane forest, respectively. Dalbergia frutescens (Vell.) Britton var. frutescens, a liana, was sampled in montane forest. All species investigated showed distinctive formation of annual growth rings. Reactivation of the vascular cambium was observed at the end of spring, and it remained active during the summer. Thereafter, cambial activity either ceased or declined dramatically at the end of autumn. Similar to the tree species studied, cambial activity in D. frutescens var. frutescens showed similar seasonal cambial activity throughout the year. Based on both direct and indirect methods, our results showed that cambial activity and wood formation only occurred during the rainy season, suggesting the potential of these species for use in dendrochronological studies.

Studies on Design Optimization of Coronary Stents

2008 ◽  
Vol 2 (1) ◽  
Author(s):  
K. Srinivas ◽  
T. Nakayama ◽  
M. Ohta ◽  
S. Obayashi ◽  
T. Yamaguchi
Keyword(s):  
Design Optimization ◽  
Cross Sections ◽  
Latin Hypercube Sampling ◽  
Coronary Stents ◽  
Point Of View ◽  
Two Dimensional ◽  
Reattachment Length ◽  
Design Variables ◽  
Two Dimensional Flow ◽  
The Relationship

The stent design itself seems to be one of the factors responsible for restenosis. As a remedy, the present work attempts to perform a design optimization of coronary stents from a hemodynamic point of view. For the purpose, we have applied the principles of modern exploration of design space restricting ourselves to two-dimensional considerations. Width, thickness, and spacing of the struts of the stent formed the design variables. The objectives chosen for optimization were the vorticity generated, length of recirculation zone, and the reattachment distance in between the struts. Both semicircular and rectangular cross sections of stents were included. Starting with the range of design variables, sample stent cases were generated using Latin hypercube sampling. Objective functions were calculated for each of these by computing the two-dimensional flow using software FLUENT under the assumption of a steady, Newtonian flow considering a model stent with three struts. This was followed by Kriging to construct a response surface, which gives the relationship between the objectives and the design variables. The procedure gave nondominated fronts, which consist of optimized designs. Stents with minimum vorticity, with minimum recirculation distance, and the ones with maximum reattachment length in between struts were generated. The procedure is capable of producing the optimum set of design variables to achieve the prescribed objectives.

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