O artigo apresenta as técnicas da voltametria cíclica e da voltametria de varrimento linear unidirecional, que são métodos eletroquímicos extremamente úteis e versáteis no estudo do comportamento de um metal ou liga, face a ambientes mais ou menos agressivos. As potencialidades das técnicas são realçadas, assim como as vantagens introduzidas pela instrumentação digital. Trata-se de um artigo de divulgação, tendo por objetivo ser acessível a engenheiros, técnicos e outros, a trabalhar na área da corrosão. Para exemplificar o tipo de informação que pode ser obtida são apresentados resultados de vários estudos realizados pelos autores.

This paper presents the electrochemical techniques, named cyclic voltammetry (CV) and linear sweep voltammetry (LSV), powerful and useful techniques for the evaluation of the behavior of metals and metallic alloys, when submitted to aggressive environments. The potentialities of the techniques are presented. The advantages brought by digital instrumentation are also emphasized. The paper is addressed to engineers, technicians and others, working on the area of corrosion. The type of information that can be obtained is exemplified with data from studies performed by the authors.

All-optical data encryption is a promising technology that could lead communication systems to an unprecedented degree of security. In this paper we use computer simulations to systematically investigate a new all-optical cryptography technique that is bit-rate independent and transparent to modulation formats. Encryption encompasses signal spectral slicing followed by two encoding stages that impose different attenuations and delays to each of the spectral slices. We analyze the quality of the encoded signal by evaluating its bit error rate (BER) performance. Results indicate that such BER may achieve 45 and 28%, respectively, for input non-return-to-zero on-off keying (NRZ-OOK) and differential quadrature phase-shift keying (DQPSK) signals. At the receiver side, results suggest that signals may be properly decoded after propagation distances that are compatible with those utilized in metropolitan area networks. The robustness of the technique against waveform analysis and brute force attacks is also approached.

The clear cell carcinoma is a rare neoplam of low level grade that develops almost exclusively in human minor salivary glands. The objective of this present work is to analyze the structural, histochemical and inmunohistochemical (IHQ) characteristics of two cases of parotid clear cell carcinoma and make a differential diagnosis with other primary and metastatic salivary tumors that clear cells show. Serial cuts of both tumors were processed for H/E, Masson and Dane trichromes, Toluidine blue, Alcian blue, PAS and PAS/diastase; IHQ marking of both high-and low-molecular weight cytokeratins, ki67, HMB45, p63 and S-100 protein. The structural pattern of these tumors were determined by nests and cords of clear cells delimited by a stroma non hyaline. In a tumor a malign neoplasia was observed in clear cells with anaplasia. The ki67 expression was important. The other tumor was constitued of clear monomorph cells without manifestation signs of atypia and almost no ki67 expression. With PAS was confirmed the presence of glycogen and not observed an important development of the collagen stroma in both neoplasms. Both cases resulted very positive the immunostaining of both high and low molecular weight cytokeratins. It resulted negative for the HMB45 and p63. The protein S-100 has it´s expression in isolated cells. We conclude that: the presented cases are very uncommon localization (parotid) as described by the literature; it matches a non hyalinizing variety because a very important hyalinized collagen stroma is not present, both primary tumors of salivary glands, of epithelial origin, non melanocytic, renal or hematopoietic lymphomas which shows immunostaining IHQ.

El carcinoma de células claras es una neoplasia rara de bajo grado que se desarrolla casi exclusivamente en glándulas salivales menores humanas. El objetivo de esta comunicación es analizar las características estructurales, histoquímicas e inmunohistoquímicas (IHQ) de dos casos de carcinoma de células claras de parótida y realizar el diagnóstico diferencial con otros tumores salivales primarios y metastásicos que presentan células claras. Cortes de ambos tumores fueron procesados para H/E, tricrómicos de Masson y Dane, Azul de toluidina, Azul alciano, PAS y PAS/diastasa; marcaciones IHQ para citoqueratinas de bajo y alto peso molecular, ki67, HMB45, p63 y proteína S-100. El patrón estructural de estos tumores estaba determinado por nidos y cordones de células claras delimitados por un estroma no hialinizado. En un tumor se observó una neoplasia maligna a células claras con manifiesta anaplasia. La expresión de ki67 fue importante. El otro tumor estaba constituido por células claras monomorfas sin signos manifiestos de atipia y casi nula expresión de ki67. Con PAS se demostró la presencia de glucógeno y no se observó un desarrollo importante del estroma colágeno en ambas neoplasias. En ambos casos resultó francamente positiva la inmunomarcación para citoqueratinas de bajo y alto peso molecular. Por el contrario resultó negativa para HMB45 y p63. La proteína S-100 tuvo su expresión en células aisladas. Se concluye que los casos presentados son de localización poco común (parótida) según lo descripto en la bibliografía; corresponden a la variedad no hialinizante ya que no está presente un importante estroma colágeno hialinizado, y ambos tumores son primarios de glándulas salivales, de origen epitelial, no melanocítico ni hematopoyético (linfomas) como lo demuestran las marcaciones IHQ.

Histologically, the adult human cerebellar cortex has three constituent layers, the molecular layer, the row of bodies of Purkinje cells and internal granular layer. The cortex of the cerebellum of mammalian embryos, as well as youth, show external granular layer. Our goal is to document morphological differences between the layers of the cerebellar cortex adult and young. Microscopic morphometric studies were performed in 20 cerebellum autopsied. The cases were divided into two groups, adults and children under 1 year. Paraffin sections were performed, stained with hematoxylin and eosin. The cortex of adult cerebellum showed morphological differences of the newborn. In the adult cerebellum has three constituent layers, whereas in the newborn has a fourth layer, the external granular.

Histológicamente la corteza del cerebelo humano adulto presenta tres capas constitutivas; la capa molecular, la hilera de los cuerpos de las células de Purkinje y la capa granulosa interna. La sustancia cortical del cerebelo de los embriones de mamífero, así como la de los jóvenes, muestran una capa granular externa. Nuestro objetivo es documentar las diferencias morfológicas entre las capas de la corteza cerebelosa adulta y joven. Se realizaron estudios morfométricos microscópicos en 20 cerebelos de autopsias. Los casos se dividieron en dos grupos, adultos y niños menores de 1 año. Se realizaron cortes en parafina, coloreados con hematoxilina y eosina. La corteza del cerebelo adulto presentó diferencias morfológicas con la de los recién nacidos. En el cerebelo adulto presenta tres capas constitutivas, mientras que en el recién nacido presenta una cuarta capa, la granulosa externa.

Com o objectivo de conservar artefactos em ferro arqueológico são testadas técnicas electroquímicas, nomeadamente a redução electrolítica e a redução galvânica. Os resultados são comparados com os obtidos pelas técnicas clássicas de simples imersão em soluções alcalinas e de redução com sulfito alcalino. Os ensaios foram efectuados em amostras retiradas de uma bala de canhão em ferro fundido de meados do século XVIII, inserida no contexto arqueológico de um navio, de nome Océan, que naufragou junto à costa sul de Portugal, em 1759. Um conjunto de amostras (núcleo e produtos de corrosão), antes e após aplicação dos métodos de tratamento foi analisado por difracção de raios - X, microscopia electrónica de varrimento e microanálise de raios - X. A eficiência dos métodos de extracção dos iões cloreto foi calculada com base na análise realizada por cromatografia iónica. Conclui-se que em condições idênticas o método de redução electrolítica foi o que conduziu a uma maior eficiência.

For the conservation of archeological iron marine artefacts, electrochemical methods have been tested, namely, the electrolytic and the galvanic reduction. Results were compared with the classical methods of simple immersion in alkaline solutions and the alkaline sulfite reduction. Experiments were performed on samples prepared from a cannon ball made with cast iron of the XVIII century, found in the archaeological context of a shipwreck, of the l`Ócean, which has occurred near the coast in the south of Portugal, in 1759. Before and after the application of the various treatments samples (core and corrosion products) have been analyzed by X-rays diffraction spectroscopy, scanning electron microscopy and X-rays electron dispersion spectroscopy. The efficiency of the methods for the extraction of chloride ions has been evaluated by the analysis performed by ionic chromatography. It was concluded that under identical conditions the electrolytic reduction was the method leading to the highest efficiency.

Proline, glicine betaíne and total soluble protein contents were determined in 12 Cuban wheat varieties, of T. aestivum and T. durum species, growing under saline conditions. Thus, two experimental variants were conducted based on a concentrated nutrient solution. The first treatment became salty with NaCl to an electric conductivity of 8 dS.m-1 and the control treatment without applying NaCl. This test was performed under hidropony conditions and treatments were applied from sowing time until 45 days after seed germination, when determinations were recorded. Data obtained in the control and stress treatments were compared by t-student test for 5 and 1 % significant levels. As a result, an important increment of proline content was obtained in most varieties, the accumulation in foliage being bigger than in roots. Glicine betaíne content was highly significant just in wheat varieties of T. durum species. Total soluble protein content showed a rather variable behaviour, even among varieties from the same species; that is why it was not considered an efficient indicator of salinity tolerance. The varieties Cuba-C-204, INIFAT RM-36, INIFAT RM-37 and INIFAT RM-26 showed the highest proline accumulation.

En este experimento se determinaron los contenidos de prolina, glicina betaína y proteínas solubles totales en 12 variedades cubanas de trigo, de las especies T. aestivum y T. durum, cultivadas en condiciones salinas. Para ello se montaron dos variantes experimentales basadas en una solución nutritiva concentrada. El primer tratamiento se salinizó con NaCl a una conductividad eléctrica de 8 dS.m-1 y el tratamiento control sin aplicar NaCl. Este ensayo se realizó en condiciones de hidroponía y los tratamientos se aplicaron desde el momento de la siembra hasta los 45 días de germinadas las semillas, cuando se realizaron las determinaciones. Los datos obtenidos en los tratamientos control y de estrés se compararon por la prueba de t-student para los niveles de significación del 5 y 1 %. Como resultado se obtuvo un significativo incremento del contenido de prolina en la mayoría de las variedades, siendo mayor la acumulación en el follaje que en las raíces. El contenido de glicina betaína solo fue altamente significativo en las variedades de trigo de la especie T. durum. El contenido de proteínas solubles totales presentó un comportamiento muy variable, incluso entre variedades de la misma especie, por lo que no se consideró un indicador eficiente de tolerancia a la salinidad. Las variedades Cuba C-204, INIFAT RM-26, INIFAT RM-37 e INIFAT RM-26 fueron las de mejor acumulación de prolina.

Salinity tolerance was studied in seven triticale lines at the early and final growing stages. Thus, two experimental trials were performed: a saline treatment with an electric conductivity (EC) of 10 dS.m-1 and a control one with EC= 0.02 dS.m-1. The following variables were evaluated at the first experiment: water uptake, seedling height, root length and fresh and dry biomass accumulation. Yield components were evaluated at the second experiment. All data were expressed in relative values to the control. A characterization based on its relative tolerance degree for both stages was done through a cluster analysis. Consequently, there was a wide variability on stress response over both phenophases. Just a single line (ITSN-14) was tolerant; however, indexes were higher than those previously reported in triticales, so they are recommended to be evaluated by means of other more accurate physiological and biochemical salinity-tolerant indicators.

Se estudió la tolerancia a la salinidad de siete líneas de triticales en los estadios tempranos y finales del desarrollo. Para ello se montaron dos variantes experimentales: un tratamiento salino con una conductividad eléctrica (CE) de 10 dS.m-1 y un tratamiento control con CE=0.02 dS.m-1. En el primer ensayo se evaluaron las variables: absorción de agua, altura de las plántulas, longitud de la raíz y acumulación de biomasas fresca y seca. La evaluación en las etapas finales se realizó mediante el estudio de los componentes del rendimiento. Todos los datos se expresaron en valores relativos al control. Mediante un análisis de conglomerados jerárquico se realizó una caracterización en cuanto a su grado de tolerancia relativa para ambos estadios. Como resultado se obtuvo una amplia variabilidad en la respuesta al estrés en las dos fenofases. Solo se observó tolerancia en una línea (ITSN-14); sin embargo, los índices fueron altos en relación con los informes encontrados en esta especie, por lo que se recomienda evaluarlas mediante el uso de otros indicadores fisiológicos y bioquímicos más precisos de tolerancia a la salinidad.

Chlorophyll (a) content and ion accumulation were determined at different plant organs of a Cuban bread wheat variety, Cuba-C-204, by applying different salinity stress levels by NaCl adjusted to electric conductivities (CE) of 4, 8 and 12 dS.m-1, and a control treatment with distilled water and CE of 0.02 dS.m-1. Dry matter accumulation per organ and root/shoot relationship was also calculated. Such determinations were performed at seedling and flowering stages following the validated methodologies. A chlorophyll content reduction was recorded as salt concentrations increased, which were just significant between the control and 12 dS.m-1. There was a significant negative correlation between chlorophyll content and Na in leaves during both stages studied, whereas the other microelements did not show this behavior. A root dry weight reduction was recorded as salt concentration increased. When evaluating leaf cation content, there was a negative correlation between K+ and Na+ contents, which proves there is a nutritional interference as an adverse salinity effect on the wheat variety studied. Consequently, as a result of the nutritional effect, chlorophyll content decreased significantly when CE surpassed 8 dS.m-1.

Se determinaron el contenido de clorofila (a) y la acumulación de iones en diferentes órganos de las plantas de la variedad cubana de trigo harinero Cuba-C-204, aplicando diferentes niveles de estrés salino por NaCl ajustados a conductividades eléctricas (CE) de 4, 8 y 12 dS.m-1, y un tratamiento control con agua destilada y CE de 0.02 dS.m-1. Se calculó, además, la acumulación de materia seca por órgano y relación raíz/follaje. Tales determinaciones se realizaron en las fenofases de plántula y floración siguiendo las metodologías validadas. Se encontró una disminución del contenido de clorofilas a medida que se incrementaron las concentraciones de sales, que solo fueron significativas entre el control y 12 dS.m-1. Se registró una correlación negativa significativa entre el contenido de clorofilas y sodio en follaje durante las dos fenofases estudiadas, mientras que los restantes microelementos no mostraron este comportamiento. Se produjo una disminución del peso seco de la raíz a medida que aumentó la concentración de sales. En la evaluación del contenido foliar de cationes, se encontró correlación negativa entre los contenidos de K+ y Na+, lo que demuestra la existencia de interferencia nutricional como efecto adverso de la salinidad en la variedad de trigo estudiada. Como consecuencia del efecto nutricional, el contenido de clorofilas disminuyó significativamente cuando CE superó los 8 dS.m-1.

The Laser used correctly in the medical practice offers clear advantages compared with traditional therapies. The improvement and even the elimination of many significant skin lesions can be achieved with reduced risks to patients. However, it is important to keep security measures and understand the possible effects on an experimental model. The chick embryo is a good model to evaluate the direct effects of non-ionizing radiation for its easy handling and availability. The purpose of this communication is to show our histological findings in organs of the chick embryo with and without protective barrier to be subjected to radiation excimer. We used the following issuers: intense pulsed light (excimer Xe-Cl laser of 308 nm wavelength). It was irradiated embryos through an open window on eggshells. Aseptically the eggs were kept for 24 hours in an incubator. The protective barriers were used with and without colored glass, latex, cellophane, paper, polycarbonate of different colors and thicknesses. The most outstanding results, with no barrier and barriers with transparent and green were intense marked congestion in capillaries, edema and focus the necrosis. We concluded that the tissue changes observed are consistent with possible side effects of these radiations fototérmicos we warned about possible side effects when they are applied indiscriminately. We believe it is important to explore different means to safeguard the safety of operators and patients.

El láser utilizado correctamente en la práctica médica ofrece claras ventajas cuando se compara con las terapias tradicionales. La mejoría e incluso la eliminación significativa de muchas lesiones cutáneas se pueden lograr con riesgos reducidos para los pacientes. Sin embargo, es importante guardar medidas de seguridad y conocer los posibles efectos en un modelo experimental. El embrión de pollo es un buen modelo para evaluar los efectos directos de radiaciones no ionizantes por su fácil manipulación y disponibilidad. El objetivo del presente trabajo es comunicar los cambios histopatológicos en órganos del embrión de pollo con y sin barrera de protección al ser sometido a radiación excimer. Se utilizó el siguiente elemento emisor: luz pulsada intensa (Xe-Cl excimer laser de 308 nm de longitud de onda. Se irradiaron los embriones a través de una ventana abierta en la cáscara del huevo. Los huevos fueron mantenidos asépticamente por 24 hs en una incubadora. Las barreras de protección utilizadas fueron vidrio con y sin color, latex, celofán, papel, policarbonato de diferentes colores y espesores. Los resultados más sobresalientes, sin barrera y con barreras transparentes y de color verde fueron: intensa vasocongestión, edema y focosde necrosis. Se concluye que las modificaciones tisulares observadas son compatibles con posibles efectos fototérmicos colaterales de estas radiaciones los que nos advierten sobre posibles efectos adversos cuando las mismas se aplican indiscriminadamente. Creemos que es de importancia estudiar los diferentes medios que permitan resguardar la seguridad de los pacientes y operadores.

O presente artigo reporta um estudo sobre uma moeda portuguesa, o Real Branco de D. João I, datável entre 1415 e 1433, encontrada durante as escavações arqueológicas na villa romana de São Pedro, em Fronteira (Alentejo, Portugal). A composição e morfologia das patinas, bem como a composição da liga utilizada no fabrico da moeda, foram analisadas utilizando apenas técnicas não destrutivas, nomeadamente, microscopia óptica (MO), microscopia electrónica de varrimento (MEV), espectroscopia de energia dispersiva de raios-X (EDX) e difracção de raios-X de pós (DRX). Os resultados foram coerentes com a informação histórica.

This paper reports data from a study carried out on a portuguese coin, the Real Branco from D. João I, found in the archaeological site of the Roman Villa of São Pedro, in Fronteira (Alentejo, Portugal). Characterization of the corrosion products, surface morphology and elemental composition of the coin was performed using non-destructive techniques, namely, optical microscopy (OM), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and powder X-ray diffraction spectroscopy (XRD). The obtained results were consistent with the historical data.

É do conhecimento geral que os valores do potencial de ruptura da passivação (Eb) e do potencial em circuito aberto (Eocp) são parâmetros importantes para avaliar a resistência à corrosão dos materiais metálicos. Contudo, pelo menos no que se refere a aços inoxidáveis a literatura apresenta resultados muito divergentes. Vários factores poderão contribuir para a referida diversidade de valores, entre eles, o acabamento ou tratamento final da superfície. Este estudo pretende avaliar a influência do acabamento superficial na rugosidade média (Ra), tensão residual (t) e resposta electroquímica dos aços em estudo. De modo a serem atingidos os objectivos foram preparadas amostras de ambos os aços com diferentes acabamentos com lixas de SiC, sendo efectuadas medidas de rugosidade, de tensão residual e realizados ensaios electroquímicos de polarização potenciodinâmica. Os ensaios electroquímicos foram realizados na célula Avesta com amostras de ambos os aços com diferentes acabamentos superficiais, em soluções aquosas de NaCl 1 M e MgCl2 0,5 M. Das medidas efectuadas conclui-se que não há uma variação significativa nos valores de Eocp e Eb com o aumento da rugosidade média para os dois aços em estudo, tanto no meio de cloreto de sódio como no meio de cloreto de magnésio. Pelo que se conclui que o tratamento final e composição da solução, no que se refere ao catião, não afectam significativamente os parâmetros electroquímicos.

It is well known that the breakdown potential (Eb) and the open circuit potential (Eocp) are important parameters to evaluate the resistance of metallic materials against corrosion. Nevertheless, the literature presents scattered values of these parameters for stainless steels (SS). Many factors may contribute to this dispersion of published Eb and Eocp values. It has been proposed that the finishing and/or final treatment of the surface is one of those factors. To address this question, the influence of the surface finishing on the average roughness (Ra), residual stress (t) and electrochemical behaviour of DIN 1.4404 and DIN 1.4410 have been considered. Samples from both steels were prepared with different finishing degrees with SiC paper. Roughness, residual stress and electrochemical tests were performed on samples with various surface finishing. Electrochemical studies were conducted in an Avesta cell and steel electrodes immersed in 1 M NaCl or 0.5 M MgCl2 aqueous solutions. We found that when steels are immersed in sodium chloride or magnesium chloride aqueous solutions there is no significant change in the variation of the Eocp and Eb values as the average roughness increases and therefore we can conclude that these parameters are not affected by the final treatment or by the solution composition.

Salinity effect on the phenology, yield and its components was studied in wheat varieties established in the eastern part of the country, which had been obtained or selected in Cuba. Twelve varieties were established in ponds from the experimental area of “J. Dimitrov” Agricultural Research Institute using two experimental variants: a saline treatment with irrigation at an electric conductivity (EC) of 8 dS.m-1 and a control treatment EC=0.02 dS.m-1. Results indicated that salinity susceptibility in wheat appears at flowering and such damages are more notable in T. durum. The most affected yield variable by salinity was full grain number per spike; consequently, there were mean yield effects from 13 to 68 %. These results enabled to classify varieties with different tolerance indexes to saline stress

Se estudió el efecto de la salinidad en la fenología, el rendimiento y sus componentes en variedades de trigo establecidas en el oriente del país, obtenidas o seleccionadas en Cuba. Doce variedades fueron establecidas en estanques del área experimental del IIA “J. Dimitrov” sometidas a dos variantes experimentales: tratamiento salino con riegos a una conductividad eléctrica (CE)=8 dS.m-1 y tratamiento control CE=0.02 dS.m-1. Los resultados indicaron que en trigo la susceptibilidad a la salinidad aparece a partir de la floración y estos daños son más marcados en la especie T. durum. La variable del rendimiento de mayores afectaciones fue el número de granos llenos por espiga y como consecuencia existieron afectaciones medias del rendimiento entre 13 y 68 %. Tales resultados permitieron clasificar variedades con diferentes índices de tolerancia al estrés salino

Estudou-se a filogenia do gene da miogenina, um membro da família MyoD, reguladora da miogênese, que ocorre durante o desenvolvimento embrionário, e sua história evolutiva em espécies domésticas que apresentem seqüências de DNA depositadas no Genbank, comparando-se o índice de substituição de nucleotídeos não-sinônimos pelo índice de substituição sinônima. Valores maiores do que um (1) indicaram que o gene sofreu mudanças que tornaram o organismo mais adaptado ao ambiente. As árvores filogenéticas foram obtidas por máxima verossimilhança, e os índices de substituição sinônima e não-sinônima foram analisadas pelo método de parcimônia. Os resultados indicaram que, provavelmente, o gene sofreu evolução adaptativa no grupo Ruminantia, Bos taurus e Ovis aries, depois que essas espécies divergiram do ancestral comum. Para as outras espécies analisadas, o gene parece ter evoluído de modo conservativo.

The myogenin gene, a member of the MyoD gene family, is a regulator of the myogenesis that takes place during the embryonic development. The objective of this study was to perform a phylogenic analysis of the myogenin gene to study its evolutionary history in the domestic species that have the sequencing data deposited in the Genbank. One common method to detect a gene evolution is made by comparing the ratio of nonsynonymous nucleotide substitution by the ratio of synonymous substitutions. Values greater than one (1) means that the gene has gone through changes that made the organism more adapted to the environment. The phylogenetic trees were obtained by maximum likelihood and the synonymous and nonsynonymous substitution rates were analyzed by the parsimony method. The results point out that probably the gene suffered an adaptive evolution in the Ruminantia group, Bos Taurus and Ovis aries, after these species diverged from their common ancestral. In the other species, the gene seems to be evolved in a conservative way.

Este trabalho teve por objetivo avaliar os efeitos de diferentes doses de lodo de esgoto na condutividade hidráulica saturada e não saturada de um Latossolo Vermelho eutroférrico (Oxisol) durante dois anos consecutivos. O experimento foi instalado no campo, com delineamento em blocos ao acaso com três repetições com os seguintes tratamentos: testemunha e adubação orgânica com lodo de esgoto em doses crescentes de 6, 12, 18, 24 e 36 Mg ha-1 em base seca e complementação mineral. As medições de condutividade foram realizadas no campo com infiltrômetro de sucção controlada para os potenciais matriciais 0, -1, -3 e -6 kPa. Nas condições em que foi realizado este experimento, concluiu-se que a dose de 12 Mg ha-1 de lodo de esgoto alterou a condutividade hidráulica nos potenciais 0 e -1 kPa, respectivamente.

This work aimed to evaluate the effects of sewage sludge application on the saturated and unsaturated hydraulic conductivity of a eutrophyc Red Latosol (Oxisol) during two consecutive years. This field experiment was conducted in a complete randomized block design with 3 replications and with the following treatments: control and increasing doses organic fertilization with sewage sludge (6, 12, 18, 24, and 36 Mg ha-1 on a dry basis) and mineral supplementation. The conductivity was measured in the field with a controlled suction infiltrometer for the matric potentials of 0, -1, -3 and -6 kPa. Under the experimental conditions of the present experiment, it was concluded that a sewage sludge dose of 12 Mg ha-1 altered the hydraulic conductivity at the potentials of 0 and -1 kPa, respectively.

As modificações estruturais causadas no solo pelos diferentes sistemas de manejo podem resultar em maior ou menor compactação, que poderá interferir na densidade do solo, na porosidade, na infiltração de água no solo e no desenvolvimento radicular das culturas. Assim, este trabalho teve como objetivo estudar, em condições de campo, os efeitos da estrutura, umidade e resistência do solo à penetração no desenvolvimento do sistema radicular do milho (Zea mays), sob sistema convencional (aração mais grade niveladora há mais de dez anos) e plantio direto (há mais de vinte anos). As avaliações foram realizadas em um Latossolo Roxo argiloso, na região norte do estado do Paraná - Brasil, cultivado com milho, no verão, e trigo, no inverno. Os resultados mostraram que valores de resistência do solo à penetração superiores a 3,5 MPa não restringiram desenvolvimento radicular do milho, porém influenciaram a sua morfologia. O plantio direto apresentou melhores condições de continuidade estrutural para o desenvolvimento radicular do que o sistema convencional, tendo sido sua resistência mais afetada pela distribuição estrutural do que pela umidade do solo.

The structural modifications caused by the different management systems to the soil can result in greater or lower compaction, which may change bulk density, porosity, water infiltration in the soil and crop root development. The present work aims to study the effects of structure soil moisture and soil resistance in the distribution of the corn root system in clay soil and under field condition, using conventional system (plowing plus leveler grille) for over 10 years, and no-tillage for over 20 years. Evaluations were carried out in "Dusky-Red Latosol" (Oxisol) in the northern region of Paraná, Brazil which was cultivated with corn during the summer and wheat in the winter. The results showed that soil resistance penetration values greater than 3.5 MPa did not constrained the corn root system development, but influenced its morphology. No-tillage system presented better structural conditions for root development than the conventional tillage and its resistence was much more affected by its structural distribution than by the soil moisture content.