Power law distribution in education: Effect of economical, teaching, and study conditions in university entrance examination

We studied the statistical distribution of student's performance, which is measured through their marks, in university entrance examination (Vestibular) of UNESP (Universidade Estadual Paulista) with respect to (i) period of study - day versus night period (ii) teaching conditions - private versus public school (iii) economical conditions - high versus low family income. We observed long ubiquitous power law tails in physical and biological sciences in all cases. The mean value increases with better study conditions followed by better teaching and economical conditions. In humanities, the distribution is close to normal distribution with very small tail. This indicates that these power law tails in science subjects axe due to the nature of the subjects themselves. Further and better study, teaching and economical conditions axe more important for physical and biological sciences in comparison to humanities at this level of study. We explain these statistical distributions through Gradually Truncated Power law distributions. We discuss the possible reason for this peculiar behavior.

PURIFICATION AND PROPERTIES OF SHIKIMATE DEHYDROGENASE FROM CUCUMBER (CUCUMIS-SATIVUS L)

Shikimate dehydrogenase (SDH, EC 1.1.1.25) extracted from cucumber pulp (Cucumis sativus L.) was purified 7-fold by precipitation with ammonium sulfate and elution from columns of Sephadex G-25, DEAE-cellulose, and hydroxyapatite. Two activity bands were detected on polyacrylamide gel electrophoresis at the last purification step. pH optimum was 8.7, and molecular weight of 45 000 was estimated on a Sephadex G-100 column. SDH was inhibited competitively by protocatechuic acid with a K(i) value of 2 x 10-4 M. K(m) values of 6 x 10-5 and 1 x 10-5 M were determined for shikimic acid and NADP+, respectively. The enzyme was completely inhibited by HgCl2 and p-(chloromercuri)benzoate (PCMB). NaCl and KCl showed partial protection against inhibition by PCMB. Heat inactivation between 50 and 55-degrees-C was biphasic, and the enzyme was completely inactivated after 10 min at 60-degrees-C. Incubation of SDH with either NADP+ or shikimic acid protected the enzyme against heat inactivation.

Pattern of nucleolar activity during spermiogenesis in triatomines (Heteroptera, Reduviidae) as analysed by silver staining

Nucleoli are the sites of biosynthesis of ribosomal precursors. In this work the nucleolar activity at interphase and the meiotic cells of the testis in five species of triatomines were analysed by means of silver staining. Several nucleolar blocks in the polyploid nuclei of testicular tubules were observed, whereas only one nucleolar body could be seen in the spermatogonial nuclei of all five species. A single nucleolar body was evident in the 'confused stage' of Triatoma brasiliensis, T. delpontei, T. lecticularia and T. rubrovaria, while T. sordida presented two nucleolar dots. The existence of small, silver-stained dots in some metaphase I chromosomes of T. brasiliensis and T. sordida is reported. The number of nucleolar dots present in spermatids of each species varied within and among species. It is suggested that in addition to providing information on rRNA biosynthesis, studies of nucleolar organizing activity can also be important sources of data on differentiation patterns and species development.

Relaxation and tunnelling of structural units within the LTO phase of La2CuO4

The anelastic relaxation (elastic energy loss and Young modulus) of nearly stoichiometric La2CuO4+delta with LTO structure was measured. Extraordinarily intense effects are present below room temperature in the elastic dynamic susceptibility, indicating relaxational dynamics of a relevant fraction of the lattice. The involved degrees of freedom are identified as rotations of the CuO6 octahedra. Two distinct processes are found at frequencies around 1 kKz: one is observed around 150 K and is characterized by a mean activation energy of 2800 K; the second one occurs below 30 K and is governed by atomic tunnelling. Two explanations are proposed for the faster process: i) formation of fluctuating LTT domains on a scale of few atomic cells; ii) the LTO phase is a dynamical Jahn-Teller phase with all the octahedra tunneling between two LTT-like tilts. In both cases there would be important implications regarding the mechanisms giving rise to charge nanophase separation and strong electron-phonon coupling.

Cytogenetics of three Brazilian Goniosoma species: A new record for diploid number in Laniatores (Opiliones, Gonyleptidae, Goniosomatinae)

Currently, 60 species of harvestmen have been karyotyped and all of these are from the Nearctic and Palearctic regions. This work is the first cytogenetic report of three gonyleptid species of the suborder Laniatores: Goniosoina aff. badiuln, G. proxiinuni and G. spelaeum of the Neotropical region, from the southeastern region of Brazil. Conventional Giemsa stain chromosome preparations were obtained from embryonic cells and adult male testes. Embryo mitotic plates of G. aff. badium and G. proximum indicated 88 chromosomes, and mitotic spermatogonial plates of G. spelaeum males revealed intra- and interindividual variation of chromosome number, ranging from 92-109 chromosomes. In the three analyzed species, the mitotic chromosomes were meta- or subinetacentric with no obvious sex chromosomes being identified during mitosis. Prophase I spermatocytes of G. spelaeum also revealed intra- and interindividual bivalent number variation and furthermore indicated the presence of multivalence. The karyotypes of these three Goniosoina species exhibited the largest chromosome pair with a negative heteropycnosis in the distal region of the shortest arrn chromosomes of G. spelaeum submitted to silver impregnation evidenced this negative heteropycnotic region as nucleolus organizer region (NOR). These results, when compared with cytogenetic data of other Laniatores species from the Palearctic region, indicated that a new record for diploid chromosome number probably characterize the genus Goniosoma in the Neotropical region.