Rubber Additions into Concrete and Gamma Radiation Effects on Mechanical Properties and Microwave Absorption Capacity

Rubber is the indispensable raw material for the manufacture of tires; it is obtained from plants, trees and currently can be produced synthetically. The tire rubber is mixed with compounds such as carbon black, sulfur, cement, paints, antioxidants, oils and fats, steel wire, almost etc., making impossible to recycle the tires itself. In this work, we investigate, the effects of the incorporation of ground rubber in concrete, mixture designed to establish the possibility of being used in the construction industry. The samples of concrete were addition with, 5 vol. %., 15 vol. % and 25 vol. % of rubber. Samples with different rubber addition were irradiated by a cobalt 60 gamma source to study the effect on their mechanical compression properties and microwave absorption capacity. Likewise, the microwave absorption capacity was studied for both irradiated and the non-irradiated. It was found that between 5 vol. % and 15 vol. % of rubber addition change the mechanical properties approximately 25 %, higher rubber additions result in a decrease in a 75 % of its mechanical properties. The fracture behavior is not the expected one due to as the curves of stress vs. strain show a double slope, which is associated with the concrete porosity and rubber content. The aging with the gamma rays generates loss of mechanical properties, especially at lower rubber addition, since at content greater than 15 Vol % the radiation effect is less. These rubber additions allow moderate deformations in compression, thus contributing to the care and preservation of the environment

Aharonov-Casher effect for spin one particles in a noncommutative space

In this work the Aharonov-Casher (AC) phase is calculated for spin one particles in a noncommutative space. The AC phase has previously been calculated from the Dirac equation in a noncommutative space using a gauge-like technique [17]. In the spin-one, we use kemmer equation to calculate the phase in a similar manner. It is shown that the holonomy receives non-trivial kinematical corrections. By comparing the new result with the already known spin 1/2 case, one may conjecture a generalized formula for the corrections to holonomy for higher spins.Comment: 9 page

Measurements of Neutrons In A Mixed GammaNeutron Field Using Three Different Types of Detectors

A linear electron accelerator for medical use is a device for the treatment of tumors by collimated beams of electrons and/or photons. These accelerators are devices that employ electromagnetic waves of high frequency, to accelerate electrons that are used directly in the treatment of superficial tumors, or, if they are made to hit them on an appropriate target, they can produce photons of high energy destined to the treatment of deeptumors.Depending on the energy of the electrons and photons and the materials that make up the head of the accelerator and the target, this equipment will produce in addition to the aforementioned radiation, neutron fields of regular intensity. It is necessary to estimate the equivalent dose due to the neutrons themselves, the doses due to the gamma field of neutron capture, produced by the capture of thermal neutrons in the concrete of the bunker, and the gamma doses due to phenomena of neutron activation of elements of the own accelerator. It is therefore important to be able to measure (detect, quantify, dose, etc.) both photons and neutrons in these cases and others more. In this work we use three different detectors, namely a scintillator-photomultiplier system, a fast reading dosimeter and bubble detector. The idea is to measure the radiation separately and compare their results. The results obtained were the mixed gamma-neutron field spectrum, the dose due only to neutrons obtained by the bubble detectors, which is compared to the dose obtained by the second fast reading dosimeters (model 884), plus the dose obtained by the first dosimeters (model 609) and finally the dose obtained by the Victoreen dosimeter

Gamma Radiation Doses Effects on Mechanical Properties and Microwave Absorption Capacity of Rubber Doped Concrete

The main raw material for the construction industry is concrete; whose fundamental components are the fine and coarse aggregates, water and cement. For the obtaining of these materials are necessary activities that generate environmental deterioration, since the aggregates are extracted from quarries or river banks and for each ton made of cement is emitted into the atmosphere a great lot of carbon dioxide. In this way, the present work is developed with the purpose of contributing to the research that can help the conservation of basic natural resources through the use of waste polymers such as waste tire rubber, in the production of concrete, hoping to reduce its harmful environmental impact. This work focuses on the one hand, in the study of the effects of the incorporation to the concrete, of different proportions of scratched rubber coming from waste tires, on its mechanical properties and on its capacity for microwaves absorption. On the other hand, it is also studied the effect of aging by applying different doses of gamma radiation on the before mentioned properties, seeking with this the possibility that it can be used in the construction industry either as structural material or as a coating. Replacements were made between 5% and 25% of rubber in order to do not significantly affecting the mechanical properties of the concrete. The results of the mechanical and microwave tests performed on the different samples with different gamma radiation doses were compared and it was found that open the possibility of research with great benefits such as the use of waste tires in the designing of concrete mixtures and the improvement of its properties. It is considered important to point out the economic benefit in the context of sustainable development, which involves solving the problem of environmental pollution caused by waste tires, to achieve the welfare of the population by improving their quality of life

On renormalizability of the massless Thirring model

We discuss the renormalizability of the massless Thirring model in terms of the causal fermion Green functions and correlation functions of left-right fermion densities. We obtain the most general expressions for the causal two-point Green function and correlation function of left-right fermion densities with dynamical dimensions of fermion fields, parameterised by two parameters. The region of variation of these parameters is constrained by the positive definiteness of the norms of the wave functions of the states related to components of the fermion vector current. We show that the dynamical dimensions of fermion fields calculated for causal Green functions and correlation functions of left-right fermion densities can be made equal. This implies the renormalizability of the massless Thirring model in the sense that the ultra-violet cut-off dependence, appearing in the causal fermion Green functions and correlation functions of left-right fermion densities, can be removed by renormalization of the wave function of the massless Thirring fermion fields only.Comment: 17 pages, Latex, the contribution of fermions with opposite chirality is added,the parameterisation of fermion determinant by two parameters is confirmed,it is shown that dynamical dimensions of fermion fields calculated from different correlation functions can be made equal.This allows to remove the dependence on the ultra-violet cut-off by the renormalization of the wave function of Thirring fermion fields onl

Effective QED Actions: Representations, Gauge Invariance, Anomalies and Mass Expansions

We analyze and give explicit representations for the effective abelian vector gauge field actions generated by charged fermions with particular attention to the thermal regime in odd dimensions, where spectral asymmetry can be present. We show, through $\zeta-$function regularization, that both small and large gauge invariances are preserved at any temperature and for any number of fermions at the usual price of anomalies: helicity/parity invariance will be lost in even/odd dimensions, and in the latter even at zero mass. Gauge invariance dictates a very general ``Fourier'' representation of the action in terms of the holonomies that carry the novel, large gauge invariant, information. We show that large (unlike small) transformations and hence their Ward identities, are not perturbative order-preserving, and clarify the role of (properly redefined) Chern-Simons terms in this context. From a powerful representation of the action in terms of massless heat kernels, we are able to obtain rigorous gauge invariant expansions, for both small and large fermion masses, of its separate parity even and odd parts in arbitrary dimension. The representation also displays both the nonperturbative origin of a finite renormalization ambiguity, and its physical resolution by requiring decoupling at infinite mass. Finally, we illustrate these general results by explicit computation of the effective action for some physical examples of field configurations in the three dimensional case, where our conclusions on finite temperature effects may have physical relevance. Nonabelian results will be presented separately.Comment: 36 pages, RevTeX, no figure

Schild's Null Strings in Flat and Curved Backgrounds

Schild's null (tensionless) strings are discussed in certain flat and curved backgrounds. We find closed, stationary, null strings as natural configurations existing on the horizons of spacetimes which possess such null hypersurfaces. Examples of these are obtained in Schwarzschild and Rindler spacetimes. A dynamic null string is also identified in Rindler spacetime. Furthermore, a general prescription (with explicit examples) is outlined by means of which null string configurations can be obtained in a large class of cosmological backgrounds.Comment: RevTex 3.0, 14 Pages, no figure

On the Meaning of the String-Inspired Noncommutativity and its Implications

We propose an alternative interpretation for the meaning of noncommutativity of the string-inspired field theories and quantum mechanics. Arguments are presented to show that the noncommutativity generated in the stringy context should be assumed to be only between the particle coordinate observables, and not of the spacetime coordinates. Some implications of this fact for noncomutative field theories and quantum mechanics are discussed. In particular, a consistent interpretation is given for the wavefunction in quantum mechanics. An analysis of the noncommutative theories in the Schr\"odinger formulation is performed employing a generalized quantum Hamilton-Jacobi formalism. A formal structure for noncommutative quantum mechanics, richer than the one of noncommutative quantum field theory, comes out. Conditions for the classical and commutative limits of these theories have also been determined and applied in some examples.Comment: References, comments, and footnotes are included; some changes in section

Gauge Invariance, Finite Temperature and Parity Anomaly in D=3

The effective gauge field actions generated by charged fermions in $QED_3$ and $QCD_3$ can be made invariant under both small and large gauge transformations at any temperature by suitable regularization of the Dirac operator determinant, at the price of parity anomalies. We resolve the paradox that the perturbative expansion is not invariant, as manifested by the temperature dependence of the induced Chern-Simons term, by showing that large (unlike small) transformations and hence their Ward identities, are not perturbative order-preserving. Our results are illustrated through concrete examples of field configurations.Comment: 4 pages, RevTe

‘O sibling, where art thou?’ – a review of avian sibling recognition with respect to the mammalian literature

Avian literature on sibling recognition is rare compared to that developed by mammalian researchers. We compare avian and mammalian research on sibling recognition to identify why avian work is rare, how approaches differ and what avian and mammalian researchers can learn from each other. Three factors: (1) biological differences between birds and mammals, (2) conceptual biases and (3) practical constraints, appear to influence our current understanding. Avian research focuses on colonial species because sibling recognition is considered adaptive where ‘mixing potential’ of dependent young is high; research on a wider range of species, breeding systems and ecological conditions is now needed. Studies of acoustic recognition cues dominate avian literature; other types of cues (e.g. visual, olfactory) deserve further attention. The effect of gender on avian sibling recognition has yet to be investigated; mammalian work shows that gender can have important influences. Most importantly, many researchers assume that birds recognise siblings through ‘direct familiarisation’ (commonly known as associative learning or familiarity); future experiments should also incorporate tests for ‘indirect familiarisation’ (commonly known as phenotype matching). If direct familiarisation proves crucial, avian research should investigate how periods of separation influence sibling discrimination. Mammalian researchers typically interpret sibling recognition in broad functional terms (nepotism, optimal outbreeding); some avian researchers more successfully identify specific and testable adaptive explanations, with greater relevance to natural contexts. We end by reporting exciting discoveries from recent studies of avian sibling recognition that inspire further interest in this topic