Acúmulo de N, K, Ca, Mg e S na matéria seca da parte aérea de mudas de cajueiro-anão-precoce submetidas a níveis crescentes de matéria orgânica

Com o objetivo de verificar os efeitos de níveis crescentes de matéria orgânica no acúmulo de macronutrientes de porta-enxertos de cajueiro-anão-precoce em 4 estádios de crescimento, foi conduzido experimento na área experimental do Departamento de Irrigação e Drenagem da Universidade Federal do Ceará, em Fortaleza, Ceará, no período de abril a junho de 1995. Utilizou-se como substrato mistura de solo e húmus de minhoca em proporções variadas. Para o plantio, utilizou-se semente de cajueiro-anão-precoce progênie CCP-76. Os tratamentos resultaram da aplicação de cinco níveis de matéria orgânica (0; 100; 200; 300 e 400 cm³/2,5kg solo) e 4 épocas de avaliação (15; 30; 45 e 60 dias após a germinação). O delineamento experimental foi o inteiramente casualizado, em esquema de parcela subdividida, com quatro repetições e seis plantas por parcela. Amostras do material vegetal foram submetidas à digestão nítricoperclórica, para determinação de K, Ca, Mg e S, respectivamente, e sulfúrica, para determinar o N. A adição de níveis crescentes de matéria orgânica ao substrato apresentou efeito linear positivo, para o N e K, atingindo o máximo para a dose de 400 cm3. Em relação aos efeitos das épocas, verificou-se efeito linear negativo. Quanto ao Ca, Mg e S, por serem considerados de baixa mobilidade no floema, estes apresentaram tendências de concentração com o incremento de massa seca das mudas.

Evolution and sedimentology of a channel fill in the sandy braided South Saskatchewan River and its comparison to the deposits of an adjacent compound bar

The depositional stratigraphy of within-channel deposits in sandy braided rivers is dominated by a variety of barforms (both singular `unit' bars and complex `compound' bars), as well as the infill of individual channels (herein termed `channel fills'). The deposits of bars and channel fills define the key components of facies models for braided rivers and their within-channel heterogeneity, knowledge of which is important for reservoir characterization. However, few studies have sought to address the question of whether the deposits of bars and channel fills can be readily differentiated from each other. This paper presents the first quantitative study to achieve this aim, using aerial images of an evolving modern sandy braided river and geophysical imaging of its subsurface deposits. Aerial photographs taken between 2000 and 2004 document the abandonment and fill of a 1 3 km long, 80 m wide anabranch channel in the sandy braided South Saskatchewan River, Canada. Upstream river regulation traps the majority of very fine sediment and there is little clay (<1%) in the bed sediments. Channel abandonment was initiated by a series of unit bars that stalled and progressively blocked the anabranch entrance, together with dune deposition and stacking at the anabranch entrance and exit. Complete channel abandonment and subsequent fill of up to 3 m of sediment took approximately two years. Thirteen kilometres of ground-penetrating radar surveys, coupled with 18 cores, were obtained over the channel fill and an adjacent 750 m long, 400 m wide, compound bar, enabling a quantitative analysis of the channel and bar deposits. Results show that, in terms of grain-size trends, facies proportions and scale of deposits, there are only subtle differences between the channel fill and bar deposits which, therefore, renders them indistinguishable. Thus, it may be inappropriate to assign different geometric and sedimentological attributes to channel fill and bar facies in object-based models of sandy braided river alluvial architecture.

Motion artifact reduction and vessel enhancement for free-breathing navigator-gated coronary MRA using 3D k-space reordering.

Breathing-induced bulk motion of the myocardium during data acquisition may cause severe image artifacts in coronary magnetic resonance angiography (MRA). Current motion compensation strategies include breath-holding or free-breathing MR navigator gating and tracking techniques. Navigator-based techniques have been further refined by the applications of sophisticated 2D k-space reordering techniques. A further improvement in image quality and a reduction of relative scanning duration may be expected from a 3D k-space reordering scheme. Therefore, a 3D k-space reordered acquisition scheme including a 3D navigator gated and corrected segmented k-space gradient echo imaging sequence for coronary MRA was implemented. This new zonal motion-adapted acquisition and reordering technique (ZMART) was developed on the basis of a numerical simulation of the Bloch equations. The technique was implemented on a commercial 1.5T MR system, and first phantom and in vivo experiments were performed. Consistent with the results of the theoretical findings, the results obtained in the phantom studies demonstrate a significant reduction of motion artifacts when compared to conventional (non-k-space reordered) gating techniques. Preliminary in vivo findings also compare favorably with the phantom experiments and theoretical considerations. Magn Reson Med 45:645-652, 2001.

Calculation of Activity Coefficients of Uni-Univalent Electrolytes by Equations Containing No Adjustable Parameters in Aqueous Solutions at 298.15 K

Normally either the Güntelberg or Davies equation is used to predict activity coefficients of electrolytes in dilute solutions when no better equation is available. The validity of these equations and, additionally, of the parameter-free equations used in the Bates-Guggenheim convention and in the Pitzerformalism for activity coefficients were tested with experimentally determined activity coefficients of HCl, HBr, HI, LiCl, NaCl, KCl, RbCl, CsCl, NH4Cl, LiBr,NaBr and KBr in aqueous solutions at 298.15 K. The experimental activity coefficients of these electrolytes can be usually reproduced within experimental errorby means of a two-parameter equation of the Hückel type. The best Hückel equations were also determined for all electrolytes considered. The data used in the calculations of this study cover almost all reliable galvanic cell results available in the literature for the electrolytes considered. The results of the calculations reveal that the parameter-free activity coefficient equations can only beused for very dilute electrolyte solutions in thermodynamic studies.

Potentiometric titration as a method of determining the stoichiometric dissociation constants of weak acids from the thermodynamic dissociation constants of aqueous solutions at 298.15 K

The simple single-ion activity coefficient equation originating from the Debye-Hückel theory was used to determine the thermodynamic and stoichiometric dissociation constants of weak acids from data concerning galvanic cells. Electromotive force data from galvanic cells without liquid junctions, which was obtained from literature, was studied in conjuction with the potentiometric titration data relating to aqueous solutions at 298.15 K. The dissociation constants of weak acids could be determined by the presented techniques and almost all the experimental data studied could be interpreted within the range of experimental error. Potentiometric titration has been used here and the calculation methods were developed to obtain the thermodynamic and stoichiometric dissociation constants of some weak acids in aqueous solutions at 298.15 K. The ionic strength of titrated solutions were adjusted using an inert electrolyte, namely, sodium or potassium chloride. Salt content alonedetermines the ionic strength. The ionic strength of the solutions studied varied from 0.059 mol kg-1 to 0.37 mol kg-1, and in some cases up to 1.0 mol kg-1. The following substances were investigated using potentiometric titration: aceticacid, propionic acid, L-aspartic acid, L-glutamic acid and bis(2,2-dimethyl-3-oxopropanol) amine.

Superfícies de resposta do tangor 'Murcott' à fertilização com N, P e K

O valor de comercialização no mercado de fruta fresca e a maior resistência a doenças, como o declínio e a clorose variegada dos citros, comparado às variedades de laranjas, estimularam a produção de tangerinas e de 'Murcott' na última década. Por outro lado, faltam informações seguras para o diagnóstico das necessidades de adubação para esses cítricos. Assim, o presente trabalho foi planejado com os objetivos de estudar a demanda por nutrientes e estabelecer doses de fertilizantes para maximizar a produtividade e a qualidade dos frutos de tangor 'Murcott' e definir critérios de diagnóstico da análise de folhas para o manejo nutricional dessas plantas. O experimento foi desenvolvido durante seis anos, num pomar comercial da variedade Murcott sobre limoeiro 'Cravo', com 4 anos de idade. Os tratamentos foram arranjados no delineamento fatorial fracionado, do tipo ½ (4³) e constituídos por níveis de N (30; 100; 170 e 240 kg N ha-1), de P (20; 80; 140 e 200 kg ha-1 de P2O5) e de K (30; 110; 190 e 270 kg ha-1 de K2O). O N aumentou a produção média do período, enquanto o efeito do K foi negativo. Não houve efeito significativo para doses de P. A produção máxima de frutos foi obtida com as doses 155; 20 e 30 kg ha-1, respectivamente, de N, P2O5 e K2O, enquanto, para otimizar o tamanho dos frutos, foi necessário elevar a doses de K para 270 kg ha-1 de K2O. Outras características de qualidade dos frutos também foram estudas, bem como critérios para a interpretação de resultados de análises de folhas.

Hormonal regulation of (Na+,K+)-ATPase biosynthesis in the toad bladder. Effect of aldosterone and 3,5,3'-triiodo-L-thyronine.

Aldosterone stimulates transepithelial Na+ transport in the toad bladder, and thyroid hormone antagonizes this mineralocorticoid action. In the present study, we assessed the influence of these two hormones on the biosynthesis of (Na+,K+)ATPase, the major driving force of Na+ transport. Rates of enzyme synthesis were estimated by immunoprecipitation with monospecific alpha (96,000 daltons) and beta (60,000 daltons) subunit antibodies. After a 30-min pulse of intact tissue with [35S]methionine, the anti-alpha-serum recognized the 96,000-dalton alpha subunit and the anti-beta-serum, a 42,000-dalton protein, in total cell extracts. The biosynthesis rates of both these proteins were increased 2.8- and 2.4-fold respectively, over controls by 80 nM aldosterone after 18 h of hormone treatment. The hormonal effect was not apparent up to 3 h of incubation and was dose dependent between 0.2 and 20 nM aldosterone. The hormonal induction was antagonized by spironolactone (500-fold excess) but not by amiloride. The action of aldosterone thus seems to be a receptor-mediated process and a primary event independent of the Na+ permeability of the apical membrane. Thyroid hormone, on the other hand, had no effect on either basal or aldosterone-stimulated synthesis rates of both enzyme proteins. The results demonstrate a direct effect of aldosterone on gene expression of the (Na+,K+)-ATPase. Ultimately, this phenomenon could be linked to the late mineralocorticoid action of this hormone. On the other hand, thyroid hormone, in contrast to the situation in mammals, does not stimulate de novo enzyme synthesis in amphibia. Neither can the antimineralocorticoid action of thyroid hormone in the toad bladder be explained by an inhibition of the (Na+,K+)-ATPase synthesis.

Quantification of the relation between surface morphodynamics and subsurface sedimentological product in sandy braided rivers

This study uses digital elevation models and ground-penetrating radar to quantify the relation between the surface morphodynamics and subsurface sedimentology in the sandy braided South Saskatchewan River, Canada. A unique aspect of the methodology is that both digital elevation model and ground-penetrating radar data were collected from the same locations in 2004, 2005, 2006 and 2007, thus enabling the surface morphodynamics to be tied explicitly to the associated evolving depositional product. The occurrence of a large flood in 2005 also allowed the influence of discharge to be assessed with respect to the processproduct relationship. The data demonstrate that the morphology of the study reach evolved even during modest discharges, but more extensive erosion was caused by the large flood. In addition, the study reach was dominated by compound bars before the flood, but switched to being dominated by unit bars during and after the flood. The extent to which the subsurface deposits (the product') were modified by the surface morphodynamics (the process') was quantified using the changes in radar-facies recorded in sequential ground-penetrating radar surveys. These surveys reveal that during the large flood there was an increase in the proportion of facies associated with bar margin accretion and larger dunes. In subsequent years, these facies became truncated and replaced with facies associated with smaller dune sets. This analysis shows that unit bars generally become truncated more laterally than vertically and, thus, they lose the high-angle bar margin deposits and smaller scale bar-top deposits. In general, the only fragments that remain of the unit bars are dune sets, thus making identification of the original unit barform problematic. This novel data set has implications for what may ultimately become preserved in the rock record.

Deposits of the sandy braided South Saskatchewan River: Implications for the use of modern analogs in reconstructing channel dimensions in reservoir characterization

Estimation of the dimensions of fluvial geobodies from core data is a notoriously difficult problem in reservoir modeling. To try and improve such estimates and, hence, reduce uncertainty in geomodels, data on dunes, unit bars, cross-bar channels, and compound bars and their associated deposits are presented herein from the sand-bed braided South Saskatchewan River, Canada. These data are used to test models that relate the scale of the formative bed forms to the dimensions of the preserved deposits and, therefore, provide an insight as to how such deposits may be preserved over geologic time. The preservation of bed-form geometry is quantified by comparing the Alluvial architecture above and below the maximum erosion depth of the modem channel deposits. This comparison shows that there is no significant difference in the mean set thickness of dune cross-strata above and below the basal erosion surface of the contemporary channel, thus suggesting that dimensional relationships between dune deposits and the formative bed-form dimensions are likely to be valid from both recent and older deposits. The data show that estimates of mean bankfull flow depth derived from dune, unit bar, and cross-bar channel deposits are all very similar. Thus, the use of all these metrics together can provide a useful check that all components and scales of the alluvial architecture have been identified correctly when building reservoir models. The data also highlight several practical issues with identifying and applying data relating to cross-strata. For example, the deposits of unit bars were found to be severely truncated in length and width, with only approximately 10% of the mean bar-form length remaining, and thus making identification in section difficult. For similar reasons, the deposits of compound bars were found to be especially difficult to recognize, and hence, estimates of channel depth based on this method may be problematic. Where only core data are available (i.e., no outcrop data exist), formative flow depths are suggested to be best reconstructed using cross-strata formed by dunes. However, theoretical relationships between the distribution of set thicknesses and formative dune height are found to result in slight overestimates of the latter and, hence, mean bankfull flow depths derived from these measurements. This article illustrates that the preservation of fluvial cross-strata and, thus, the paleohydraulic inferences that can be drawn from them, are a function of the ratio of the size and migration rate of bed forms and the time scale of aggradation and channel migration. These factors must thus be considered when deciding on appropriate length:thickness ratios for the purposes of object-based modeling in reservoir characterization.

Copy number variation in the porcine genome inferred from a 60 k SNP BeadChip

Background: Recent studies in pigs have detected copy number variants (CNVs) using the Comparative Genomic Hybridization technique in arrays designed to cover specific porcine chromosomes. The goal of this study was to identify CNV regions (CNVRs) in swine species based on whole genome SNP genotyping chips. Results: We used predictions from three different programs (cnvPartition, PennCNV and GADA) to analyze data from the Porcine SNP60 BeadChip. A total of 49 CNVRs were identified in 55 animals from an Iberian x Landrace cross (IBMAP) according to three criteria: detected in at least two animals, contained three or more consecutive SNPs and recalled by at least two programs. Mendelian inheritance of CNVRs was confirmed in animals belonging to several generations of the IBMAP cross. Subsequently, a segregation analysis of these CNVRs was performed in 372 additional animals from the IBMAP cross and its distribution was studied in 133 unrelated pig samples from different geographical origins. Five out of seven analyzed CNVRs were validated by real time quantitative PCR, some of which coincide with well known examples of CNVs conserved across mammalian species. Conclusions: Our results illustrate the usefulness of Porcine SNP60 BeadChip to detect CNVRs and show that structural variants can not be neglected when studying the genetic variability in this species.

Metabolic responses of guava trees irrigated withdifferent N and K levels in São Francisco Valley

The guava (Psidium guajava L.) cv. Paluma has been cultivated in São Francisco Valley, Northeastern of Brazil, for in natura consumption and processing purposes. In spite of its importance, there are few scientific knowledge regarding guava physiology, nutrition, irrigation and fertigation. The objective of this work was to evaluate the effect of weather conditions and different concentrations of N and K applied by fertigation in foliar contents of reducing sugars, total soluble sugars, starch, sucrose, amino acids, and proteins. The field experiment was carried out at Bebedouro Experimental Field and the biochemical evaluations at the Laboratory of Seed and Plant Physiology, both located at Embrapa Semi-Árido, Petrolina-PE. The doses of 200 g N and 100 g K2O; 400 g N and 200 g K2O; 600 g N and 300 g K2O; and 800 g N and 400 g K2O per plant were applied in an experiment field. The experimental design was totally randomized blocks, with four treatments and five blocks. The weather conditions influenced the plant photosynthesis, which affects the plants metabolism. Guava presented specific responses to N and K fertigation for each parameter evaluated. The weather conditions during the evaluation period influenced guava responses to N and K fertigation.

Fertirrigação da bananeira cv. Prata-Anã com N e K em um argissolo vermelho-amarelo

O Nordeste brasileiro é a principal região produtora de banana, responsável por cerca de 35,80% da produção nacional. Apesar das condições favoráveis ao seu cultivo, a produtividade tem sido muito abaixo do seu potencial. Geralmente, isso se deve a problemas de suprimento hídrico e nutricional. Dentre os nutrientes, o nitrogênio (N) e o potássio (K) são requeridos em maiores quantidades pela bananeira. Com o objetivo de estudar o efeito de quatro doses de N (0; 117; 235 e 352 kg ha-1 de N) e de K (0; 157; 313 e 470 kg ha-1 de K2O), aplicados via fertirrigação, avaliaram-se características produtivas de um 2º ciclo de cultivo da banana cv. Prata-Anã, em um Argissolo Vermelho-Amarelo dos tabuleiros costeiros do Nordeste brasileiro. O N não influenciou na produção de banana, enquanto a resposta ao K foi linear. O nível crítico de K pelo Mehlich-1, na profundidade de 0,20- 0,40 m, foi 0,71 mmol c kg-1.