Euphorbia hirta L., popularmente conhecida por erva andorinha, tem sido utilizada no tratamento de distúrbios respiratórios e como antiespasmódico. Esse trabalho foi realizado com a finalidade de determinar as características macroscópicas e microscópicas das folhas, caule e raiz dessa planta, uma vez que estas são as partes usadas popularmente. Algumas características de valor na sua diagnose foram apontadas e ilustradas por fotomicrografias. Reações de fitoquímica e a determinação do conteúdo de água e de cinzas foram realizadas no pó obtido da planta inteira, parte essa utilizada na fitoterapia Ayuverda. Na prospecção fitoquímica foram encontrados flavonóides, mucilagem, resinas e cumarinas. Na determinação do teor de água, de cinzas totais e de cinzas insolúveis em ácido, os valores encontrados foram 8,99%, 9,35%, 0,75%, respectivamente. Com o desenvolvimento deste trabalho foi possível obter parâmetros para o controle de qualidade das folhas, caule e raízes de E. hirta.

The Euphorbia hirta L. has been used in the treatment of respiratory disorders and as an antispasmodic. This work was carried out to determine the macroscopic and microscopic characteristics of the leaves, stems and roots of this plant, as these parts are commonly used. Some features of value in their diagnosis were identified and illustrated by photomicrographs. Phytochemical reactions and determination of water and ash contents were carried out in the powder obtained from the whole plant, the part used in Ayurveda phytomedicine. In phytochemical screening, we found flavonoids, mucilage, resins and coumarins. The values of water content, total ashes and acid insoluble ashes were 8.99%, 9.35%, 0.75%, respectively. The data obtained are important for the quality control of the leaves, stems and roots of E. hirta.

We compute the Casimir energy for a massive scalar field constrained between two parallel planes (Dirichlet boundary conditions) in order to investigate its non-relativistic limit. Instead of employing the usual relativistic dispersion relation omega(p) = <img SRC="http:/img/fbpe/bjp/v31n1/08eq01.gif">, we use the non-relativistic one, omega(p) = p²/2m. It turns out that the Casimir energy is zero. We include the relativistic corrections perturbatively and show that at all orders the Casimir energy remains zero, since each term in the power series in 1/c² is proportional to the Riemann zeta function of a negative even integer. This puzzling result shows that, at least for the free massive scalar field, the Casimir effect is non-perturbative in the relativistic sense.

The influence of an external constant uniform magnetic field on the Casimir energy associated with a Dirac field under antiperiodic boundary condition is computed using Schwinger's method. The obtained result shows that the magnetic field enhances the fermionic Casimir energy, in oposition to the bosonic Casimir energy which is inhibited by the magnetic field.

We compute the Casimir pressure between an unusual pair of parallel plates, namely, a perfectly conducting plate (<FONT FACE="Symbol">e®¥)</font> and an infinitely permeable one (<FONT FACE="Symbol">m®¥</font>) with the generalized <FONT FACE="Symbol">z</font>-function method. The result for this problem, which has been rarely discussed in the literature, is a repulsive Casimir force. The <FONT FACE="Symbol">z</font>-function method provides a very compact and economic way of obtaining the final result.