463 research outputs found
Hamiltonization of theories with degenerate coordinates
We consider a class of Lagrangian theories where part of the coordinates does
not have any time derivatives in the Lagrange function (we call such
coordinates degenerate). We advocate that it is reasonable to reconsider the
conventional definition of singularity based on the usual Hessian and,
moreover, to simplify the conventional Hamiltonization procedure. In
particular, in such a procedure, it is not necessary to complete the degenerate
coordinates with the corresponding conjugate momenta.Comment: 14 pages, LaTex fil
Di klasen-interesen un di natsiyonale frage
https://www.ester.ee/record=b5454366*es
General quadratic gauge theory. Constraint structure, symmetries, and physical functions
How can we relate the constraint structure and constraint dynamics of the
general gauge theory in the Hamiltonian formulation with specific features of
the theory in the Lagrangian formulation, especially relate the constraint
structure with the gauge transformation structure of the Lagrangian action? How
can we construct the general expression for the gauge charge if the constraint
structure in the Hamiltonian formulation is known? Whether can we identify the
physical functions defined as commuting with first-class constraints in the
Hamiltonian formulation and the physical functions defined as gauge invariant
functions in the Lagrangian formulation? The aim of the present article is to
consider the general quadratic gauge theory and to answer the above questions
for such a theory in terms of strict assertions. To fulfill such a program, we
demonstrate the existence of the so-called superspecial phase-space variables
in terms of which the quadratic Hamiltonian action takes a simple canonical
form. On the basis of such a representation, we analyze a functional
arbitrariness in the solutions of the equations of motion of the quadratic
gauge theory and derive the general structure of symmetries by analyzing a
symmetry equation. We then use these results to identify the two definitions of
physical functions and thus prove the Dirac conjecture.Comment: LaTex file, 18 page
Canonical form of Euler-Lagrange equations and gauge symmetries
The structure of the Euler-Lagrange equations for a general Lagrangian theory
is studied. For these equations we present a reduction procedure to the
so-called canonical form. In the canonical form the equations are solved with
respect to highest-order derivatives of nongauge coordinates, whereas gauge
coordinates and their derivatives enter in the right hand sides of the
equations as arbitrary functions of time. The reduction procedure reveals
constraints in the Lagrangian formulation of singular systems and, in that
respect, is similar to the Dirac procedure in the Hamiltonian formulation.
Moreover, the reduction procedure allows one to reveal the gauge identities
between the Euler-Lagrange equations. Thus, a constructive way of finding all
the gauge generators within the Lagrangian formulation is presented. At the
same time, it is proven that for local theories all the gauge generators are
local in time operators.Comment: 27 pages, LaTex fil
NAA and STS effects on bract survival time, carbohydrate content, respiration rate and carbohydrate balance of potted Bougainvillea spectabilis Willd
The aims of this work were to deepen the knowledge on the physiology of bract abscission in Bougainvillea spectabilis âKillie Campbellâ plants, in what relates to respiration and carbon balance. Using the effects induced by Silver Thiosulphate (STS) and/or Naphtalene Acetic Acid (NAA, at high concentration: 500 mg.l-1) on bract abscission under interior conditions, the relationship between bract survival time (longevity) and, respiration rate or carbohydrate levels, was investigated.
Treatments that included NAA were the ones that reduced significantly bract abscission. Unexpectedly, the higher the levels of bract soluble and total carbohydrates, measured at day 10 postproduction (PP), the higher the abscission of bracts. These results show, for the first time, that abscission can positively correlate with non structural carbohydrates levels in the organ that abscise.
Bract respiration rate was significantly affected by treatment and postproduction day (PP). Treatments that had higher bract respiration rates (WATER and STS) also had higher levels of non structural carbohydrates in the bracts. Bract respiration rate decreased from day 10 to day 17 PP by approximately 50% (on average of all treatments) and was negatively correlated with bract survival time.
In the carbon balance per gram of bract dry weight, the treatments WATER and STS, showed the largest decrease in the content of total carbohydrates and had the highest consumption of carbohydrates through respiration. So, these were the bracts that needed to import a higher amount of carbohydrates per gram of bract dry weight. In the carbon balance for the whole mass of bracts and adjacent stems in an average plant, the treatments WATER and STS continued to allow for the largest decreases in total carbohydrate during postproduction. However, and contradicting the results per gram of bract dry weight, the highest total consumption of carbohydrates by respiration was obtained for the NAA and STS+NAA treatments. It makes sense that bracts that last longer have lower individual carbon consumption while, at the plant level, the increased number of remaining bracts causes a higher overall expenditure.
Respiration rate has been used as an indicator of flower longevity, this correlation is here extended for the flower+bract system. Plants that had higher bract respiration rates, most probably, had a higher flow of carbohydrates through the bracts (and flowers), which, in the end, was sensed as a higher carbohydrate level.Bolsa Praxis XXI/BD/15640/98
e o Projecto PBIC/C/2286/95, financiados pela Fundação para a CiĂȘncia
e Tecnologia. Financiamento Plurianual e instalaçÔes do CDCTPV/Universidade do Algarve (incluindo o Projecto de unidade I&D: CDCTPV 2003-2005, POCTI/POCI,2010
Flavonoids, Phenolics, and Antioxidant Capacity in the Flower of Eriobotrya japonica Lindl.
Flavonoids and phenolics are abundant in loquat flowers. Methanol had the highest extraction efficiency among five solvents, followed by ethanol. Considering the safety and residue, ethanol is better as extraction solvent. The average content of flavonoids and phenolics of loquat flower of five cultivars were 1.59 ± 0.24 and 7.86 ± 0.87 mg/g DW, respectively, when using ethanol as extraction solvent. The contents of both bioactive components in flowers at different developmental stages and in the various flower tissues clearly differed, with the highest flavonoids and phenolics content in flowers of stage 3 (flower fully open) and petal, respectively. The antioxidant capacity was measured using FRAP, DPPH, and ABTS methods. The values of ABTS method was highest, followed by DPPH, the lowest was FRAP, when using vitamin C equivalent antioxidant capacity (VCEAC) as unit. Correlation analysis showed that the ABTS method showed the highest correlation coefficients with flavonoids and phenolics, i.e., 0.886 and 0.973, respectively
The Experiment That did not Fail: Image and Reality in the Israeli Kibbutz
The kibbutzim of Israel show the world that communal living can be successful, and many observers have asked the questions: Can this success be repeated elsewhere? What are its lessons for other societies? In sociology, the validity and importance of comparative study and the intrinsic interest of the kibbutz way of life cannot be denied
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