Abstract:
it is quite comon in brazilian rubber plantations the occorence of boron deficiency symptoms on the leaves associated with n, p, k, and mg fertilizer programs. in a greenhouse experiment the daily aplication of five levels of boron (0.5; 1.0; 1.5; 2.0 and 2.5 ppm) to the substract induced toxicity symptoms to the leaves of the young rubber trees. tips and marginal necrosis of the leaves occured when the boron concentration in the subtract was between 1.0 and 2.5 ppm of boron. recently in an experiment carried out in order to obtain the macro and zn, mn deficiencies on grafted plants with clone rrim 600, the boron was withdraw from the nutrient solutions in order prevent toxic effects in the plants. after six months symptoms appeared which consisted of a halt on growth; the terminal buds die and an exudation of latex started. after the supply of 0.1 ppm of boron to the nutrient solutions the plants began to growth again and numerous branches started to appear in the plants.

Abstract:
we report in the present work on the use of the sound card of a pc for data acquisition in a classroom physics laboratory, instead of using analogical-digital internal or external converters. a physical pendulum experiment illustrates data acquisition via the joystick port. we explain how to use the audio in an out entrances and present a collection of related softwares available freeware on the web.

Abstract:
An assessment of the present status of the theory, some immediate tasks which are suggested thereby and some questions whose answers may require a longer breath since they relate to significant changes in the conceptual and mathematical structure of the theory.

Abstract:
The author presents a new proof of injectivity of the composition of the inverse of the rational Chern Character in homology applied to the classifying space BG of a (countable) discrete group G, restricted to dimensions less or equal than two, with the rationalized Assembly map of Kasparov into the (operator) K-Theory of the full group C^*-algebra C^*(G) (tensored with the rational numbers).

Abstract:
In the orthodox language of Quantum Mechanics the observer occupies a central position and the only "real events" are the measuring results. We argue here that this narrow view is not forced upon us by the lessons of Quantum Physics. An alternative language, closer to the intuitive picture of the working physicist in many areas, is not only possible but warranted. It needs, however, a different conceptual picture ultimately implying also a different mathematical structure. Only a rudimentary outline of this picture will be attempted here. The importance of idealizations, unavoidable in any scheme, is emphasized. A brief discussion of the EPR-phenomenon is added.

Abstract:
We consider *-linear maps into a commutative C*-algebra C (X) of continuous functions on a locally compact Hausdorff space X with certain specified properties and prove two results: (1) an extension result for a class of *-linear maps Y --> C (X) which may be called of locally compact type (locally finite) with respect to an inclusion Y < X of normed vector spaces, and (2) a minimal decomposition for certain *-linear maps into C (X) (absolutely continuous) as a difference of two positive maps.

Abstract:
The main result of the paper is an extension of the Dirichlet problem from (closures of) bounded open domains U to arbitrary compact subsets X of the complex plane, i.e. the closure of the corresponding space of functions which are harmonic in a neighbourhood of X and equipped with the supremums norm on X is shown to be isometric with the space of continuous functions C (/delta X) on its Shilov boundary (a given compact subset of X). This is used to define an extension of holomorphic function calculus with respect to certain (weakly normal) elements x of a unital operator algebra A to a completely isometric harmonic function calculus into the enveloping operator system of A. It is also shown that in case of a super C*-algebra A (operator algebra with involution) any weakly normal superpositive element x has a square root in A.

Abstract:
The article exhibits certain relations between the injective envelope I(A) of a C*-algebra A and the von Neumann algebra generated by a representation lambda of A provided it is injective. More specifically we show that there exist positive retractions sigma : /lambda (A)'' ---> I(A) which are close to being *-homomorphisms in the sense that they are Jordan homomorphisms of the underlying Jordan algebras, and the kernel of /sigma is given by a twosided ideal.