Coarse-silt-fraction mineralogy at DSDP Legs 56 and 57 Holes

Soviet sedimentologists use the term "coarse silt" to denote the size fraction 0.1 to 0.05 mm (50-100 µm). Petelin (1961) has shown that this fraction is most diagnostic for terrigeneous and volcanogenic mineral assemblages and provinces in Recent deep-sea sediments, because of its greatest variability of both heavy and light non-opaque minerals, which may be easily identified by the common immersion method. We believe that the fraction is suitable for mineralogical study of unconsolidated and friable sediments from DSDP cores as well, if the objective is to investigate their source area and transporation tracks. In the case of fine-grained oceanic sediments, mineral composition of the coarse silt does not differ markedly from that of the "coarse fraction" (>62 µm).

Geochemistry of the Japan Trench sediments at DSDP Legs 56-57 Holes

The main objective of this investigation was to study distribution of main chemical constituents and several minor elements in sediment sections drilled during DSDP Legs 56 and 57 in the Japan Trench, in order to infer geochemical features of different lithologic types of sediments, and to find out how the geochemistry is associated with major lithologic constituents, such as terrigenous detrital matter, clay, volcanic ash, and biogenic particles. The geochemical data may help to indicate the nature of the sediments and to interpret sedimentation processes. The analyzed samples seem to be representative of most lithologic units, sub-units, and sediment types drilled at all sites on both legs, except for some shallow-water deposits at Sites 438 and 439. We analyzed bulk-sediment composition by X-ray fluorescence (Kuzmina and Turanskaya) and routine wet-chemical methods (Mikhailov); amorphous SiO2, extracted in a boiling sodium carbonate solution (Analythical Laboratory, P. P. Shirshov Institute of Oceanology); Cr, Zn, Cu, Ni, Co, and Al by atomic absorption (Gordeev); and Sn, Pb, Zn, Cu, Ni, Co, Cr, V, B, and Ag by quantitative spectrographic analyses in both bulk samples and granulometric fractions (Mikhailov). In addition, Fe, Ti, Mn, and CaCO3 have been determined in selected samples by routine wet-chemical methods (Analytical Laboratory, P. P. Shirshov Institute of Oceanology). Murdmaa was responsible for interpretation of the results.

Stable isotope record of foraminifera from the Barents Sea

We measured the oxygen isotopic composition of planktonic and benthic foraminifera in three cores collected at key positions to reconstruct the paleoceanography of the Barents Sea: core ASV 880 on the path of the northern branch of Atlantic water inflowing from the Arctic Ocean, core ASV 1200 in the central basin near the polar front, and core ASV 1157 in the main area of brine formation. Modern seawater d18O measurements show that far from the coast, d18O variations are linearly linked to the salinity changes associated with sea ice melting. The foraminifer d18O records are dated by 14C measurements performed on mollusk shells, and they provide a detailed reconstruction of the paleoceanographic evolution of the Barents Sea during the Holocene. Four main steps were recognized: the terminal phase of the deglaciation with melting of the main glaciers, which were located on the surrounding continent and islands, the short thermal optimum from 7.8 ka B.P. to 6.8 ka B.P., a cold mid-Holocene phase with a large reduction of the inflow of Atlantic water, and the inception of the modern hydrological pattern by 4.7 ka B.P. Brine water formation was active during the whole Holocene. The paleoclimatic evolution of the Barents Sea was driven by both high-latitude summer insolation and the intensity of the Atlantic water inflow.

The near-bottom plankton and benthic invertebrate fauna of Josephine and Great Meteor Seamounts (Table 2)

15 samples obtained with Beyer's epibenthic closing net were studied quantitatively. The numbers of epi- and endobenthic animals were found to be correlated with the volume of sediment in the samples. Among the planktonic components, calanoid copepodes were strongly predominant. In the samples obtained on the Great Meteor Seamount, very much larger numbers of these animals were caught in the daytime than at night. Possible explanations for this difference are suggested.

(Table 1) Geochemistry of Sapropels of the Mediterranean Sea

Sapropels -organic-matter rich layers- are common in Neogene sediments of the eastern Mediterranean Sea. The formation of these layers has been attributed to climate-related increases in organic-matter production (Calvert et al., 1992, doi:10.1038/359223a0; Rossignol-Strick et al., 1982, doi:10.1038/295105a0; Rohling, 1994, doi:10.1016/0025-3227(94)90202-X) and increased organic-matter preservation due to oxygen depletion in more stagnant bottom waters (Rossignol-Strick et al., 1982, doi:10.1038/295105a0; Rohling, 1994, doi:10.1016/0025-3227(94)90202-X). Here we report that eastern Mediterranean Pliocene sapropels (Emeis et al., 1996, doi:10.2973/odp.proc.ir.160.102.1996) contain molecular fossils of a compound (isorenieratene) known to be synthesized by photosynthetic green sulphur bacteria, suggesting that sulphidic (euxinic) -and therefore anoxic- conditions prevailed in the photic zone of the water column. These sapropels also have a high trace-metal content, which is probably due to the efficient scavenging of these metals by precipitating sulphides in a euxinic water column. The abundance and sulphur-isotope composition of pyrite are consistent with iron sulphide formation in the water column. We conclude that basin-wide water-column euxinia occurred over substantial periods during Pliocene sapropel formation in the eastern Mediterranean Sea, and that the ultimate degradation of the increased organic-matter production was strongly influential in generating and sustaining the euxinic conditions.

Mineralogy of sediments at DSDP Leg 67 Hole

Seven sites were drilled during Leg 67 along a transect across the Middle America Trench off Guatemala: four (Sites 494, 496, 497, and 498) on continental slope, two (Sites 499 and 500) on Trench floor, and one (Site 495) on the Cocos Plate. We studied the mineralogy of sediments from Sites 494, 495, 496, 499, and 500. Our objective was to investigate the origin and source of separate minerals and mineral assemblages, giving special attention to the influence of the alteration of basalts on the sediment mineralogy, which we expected to be particularly important in layers just above oceanic basement.

Measuring, Modeling, and Forecasting Volatility and Correlations from High-Frequency Data

This dissertation contains four essays that all share a common purpose: developing new methodologies to exploit the potential of high-frequency data for the measurement, modeling and forecasting of financial assets volatility and correlations. The first two chapters provide useful tools for univariate applications while the last two chapters develop multivariate methodologies. In chapter 1, we introduce a new class of univariate volatility models named FloGARCH models. FloGARCH models provide a parsimonious joint model for low frequency returns and realized measures, and are sufficiently flexible to capture long memory as well as asymmetries related to leverage effects. We analyze the performances of the models in a realistic numerical study and on the basis of a data set composed of 65 equities. Using more than 10 years of high-frequency transactions, we document significant statistical gains related to the FloGARCH models in terms of in-sample fit, out-of-sample fit and forecasting accuracy compared to classical and Realized GARCH models. In chapter 2, using 12 years of high-frequency transactions for 55 U.S. stocks, we argue that combining low-frequency exogenous economic indicators with high-frequency financial data improves the ability of conditionally heteroskedastic models to forecast the volatility of returns, their full multi-step ahead conditional distribution and the multi-period Value-at-Risk. Using a refined version of the Realized LGARCH model allowing for time-varying intercept and implemented with realized kernels, we document that nominal corporate profits and term spreads have strong long-run predictive ability and generate accurate risk measures forecasts over long-horizon. The results are based on several loss functions and tests, including the Model Confidence Set. Chapter 3 is a joint work with David Veredas. We study the class of disentangled realized estimators for the integrated covariance matrix of Brownian semimartingales with finite activity jumps. These estimators separate correlations and volatilities. We analyze different combinations of quantile- and median-based realized volatilities, and four estimators of realized correlations with three synchronization schemes. Their finite sample properties are studied under four data generating processes, in presence, or not, of microstructure noise, and under synchronous and asynchronous trading. The main finding is that the pre-averaged version of disentangled estimators based on Gaussian ranks (for the correlations) and median deviations (for the volatilities) provide a precise, computationally efficient, and easy alternative to measure integrated covariances on the basis of noisy and asynchronous prices. Along these lines, a minimum variance portfolio application shows the superiority of this disentangled realized estimator in terms of numerous performance metrics. Chapter 4 is co-authored with Niels S. Hansen, Asger Lunde and Kasper V. Olesen, all affiliated with CREATES at Aarhus University. We propose to use the Realized Beta GARCH model to exploit the potential of high-frequency data in commodity markets. The model produces high quality forecasts of pairwise correlations between commodities which can be used to construct a composite covariance matrix. We evaluate the quality of this matrix in a portfolio context and compare it to models used in the industry. We demonstrate significant economic gains in a realistic setting including short selling constraints and transaction costs.

No. 63 - Abril/Junio 1997 / PUBLICACIONES ICESI

¿Es la ingeniería del software una ingeniería madura?, Londoño Acosta, Guillermo -- Comunicaciones y sociedad : el ingeniero de sistemas frente al siglo XXI, Ardila, Carlos H. ; Madrid Molina, Juan Manuel -- Telecommuting : ¿Una realidad en Colombia?, Ritter Meza, Grace Alexandra -- Una aplicación del método de análisis orientado a objetos, de Ivar Jacobson, Londoño Acosta, Guillermo ; Villegas, Pablo Andrés ; Castañeda Sánchez, Jairo ; Obonaga Palau, Alexander -- Internet, hipertexto y educación, Machado Zamorano, Juan Carlos -- Java y la programación orientada a objetos, Gamess, Eric -- Nuevas tecnologías en redes WAN y LAN, Osorio, Gustavo Adolfo ; Gil, Pedro Enrique ; Nader Rizo, Alberto Enrique ; Sandoval, Juan Carlos

Software engineering: methods, modeling and teaching

Since the emergence of software engineering in the late 1960's as a response to the software crisis, researchers throughout the world are trying to give theoretical support to this discipline. Several points of view have to be reviewed in order to complete this task. In the middle 70's Frederick Brooks Jr. coined the term "silver bullet" suggesting the solution to several problems rela-ted to software engineering and, hence, we adopted such a metaphor as a symbol for this book. Methods, modeling, and teaching are the insights reviewed in this book. Some work related to these topies is presented by software engineering researchers, led by Ivar Jacobson, one of the most remarkable researchers in this area. We hope our work will contribute to advance in giving the theoretieal support that software engineering needs.

The transcriptome of metamorphosing flatfish

Background Flatfish metamorphosis denotes the extraordinary transformation of a symmetric pelagic larva into an asymmetric benthic juvenile. Metamorphosis in vertebrates is driven by thyroid hormones (THs), but how they orchestrate the cellular, morphological and functional modifications associated with maturation to juvenile/adult states in flatfish is an enigma. Since THs act via thyroid receptors that are ligand activated transcription factors, we hypothesized that the maturation of tissues during metamorphosis should be preceded by significant modifications in the transcriptome. Targeting the unique metamorphosis of flatfish and taking advantage of the large size of Atlantic halibut (Hippoglossus hippoglossus) larvae, we determined the molecular basis of TH action using RNA sequencing. Results De novo assembly of sequences for larval head, skin and gastrointestinal tract (GI-tract) yielded 90,676, 65,530 and 38,426 contigs, respectively. More than 57 % of the assembled sequences were successfully annotated using a multi-step Blast approach. A unique set of biological processes and candidate genes were identified specifically associated with changes in morphology and function of the head, skin and GI-tract. Transcriptome dynamics during metamorphosis were mapped with SOLiD sequencing of whole larvae and revealed greater than 8,000 differentially expressed (DE) genes significantly (p < 0.05) up- or down-regulated in comparison with the juvenile stage. Candidate transcripts quantified by SOLiD and qPCR analysis were significantly (r = 0.843; p < 0.05) correlated. The majority (98 %) of DE genes during metamorphosis were not TH-responsive. TH-responsive transcripts clustered into 6 groups based on their expression pattern during metamorphosis and the majority of the 145 DE TH-responsive genes were down-regulated. Conclusions A transcriptome resource has been generated for metamorphosing Atlantic halibut and over 8,000 DE transcripts per stage were identified. Unique sets of biological processes and candidate genes were associated with changes in the head, skin and GI-tract during metamorphosis. A small proportion of DE transcripts were TH-responsive, suggesting that they trigger gene networks, signalling cascades and transcription factors, leading to the overt changes in tissue occurring during metamorphosis.

Araucaria clonal forestry: types of cuttings and mother tree sex in field survival and growth.

Araucaria angustifolia é uma espécie nativa potencial para a silvicultura brasileira. No entanto, uma série de desafios e limitações técnicas ainda persistem, dificultando sua expansão silvicultural, dentre os quais se destaca a falta de tecnologias de clonagem de materiais genéticos superiores, bem como sua avaliação em condições de campo. Assim, objetivou-se avaliar a potencialidade da utilização de mudas de araucária oriundas de estaquia e de sementes para produção madeireira, por meio da avaliação da sobrevivência e crescimento a campo. Clones provenientes de matrizes masculinas e femininas, de diferentes tipos de estacas e mudas de sementes foram plantadas em espaçamento 3 x 3 m. O experimento foi conduzido em delineamento inteiramente casualizado, com três tratamentos e parcelas de uma planta (one tree plot). Clones do sexo feminino e de estacas contendo o ápice apresentaram maior crescimento em diâmetro à altura do peito (6,4 cm) e altura total (3,6 m) aos 74 meses após o plantio, seguidas das de sementes e demais clones, com resultados similares. Conclui-se que a estaquia é uma técnica potencial de produção de mudas de araucária para fins madeireiros e é favorecida pela utilização de estacas proveniente de matrizes femininas e com ápice.

Indução de brotações epicórmicas por meio de anelamento e decepa em erva-mate.

A erva-mate (Ilex paraguariensis) é uma espécie arbórea, nativa da América do Sul e largamente consumida na forma de chá. Em ervais debilitados, a poda de recuperação é utilizada para a retomada do vigor vegetativo, bem como o anelamento, os quais estimulam a emissão de brotações. O presente trabalho teve como objetivos verificar a influência do anelamento em combinação com a aplicação de diferentes concentrações de benzil-amino-purina (BAP) e da decepa em diferentes alturas na emissão de brotações por matrizes de erva-mate de 17 e mais de 80 anos de idade, no inverno/2006 e verão/2007. O anelamento foi realizado com motosserra a uma altura de 30 cm do solo, seguido do tratamento com BAP, veiculado em pasta de vaselina, nas concentrações de 0, 150 e 300 mg Kg-1. A decepa foi realizada também com motosserra, sendo os tratamentos três alturas de corte: 15, 30 e 60 cm do solo. Após 6 e 12 meses da instalação foram avaliadas as seguintes variáveis: porcentagem de matrizes brotadas, número de brotações por árvore (ou cepa), comprimento e diâmetro das brotações. Os resultados obtidos mostram que a erva-mate tem boa capacidade de brotação, para as duas técnicas utilizadas. A eficiência na emissão de novos brotos no anelamento é influenciada pela idade da planta matriz e pela estação do ano. Os maiores valores foram obtidos no inverno/2006 e com matrizes de 17 anos de idade, chegando a 95,84% de indução de brotações. Na técnica da decepa, não foi observada influência da época de instalação na porcentagem de brotação, mas a idade da matriz e a altura do corte foram significativos para esta variável. Os maiores valores foram obtidos com matrizes de 17 anos e altura de corte a 60 cm do solo.

Indirect and expedite assessment of Ilex paraguariensis commercial yield.

A produção de biomassa comercial é uns dos principais indicadores para seleção de progênies e clones de erva-mate. Técnicas tradicionais para se obter tais informações dependem da colheita das árvores e apresentam, dentre outras limitações, elevado custo e reduzida praticidade. Assim, objetivou-se avaliar a eficiência de métodos indiretos, por meio de estimativa de biomassa comercial e escore de produtividade em função de diferentes procedências, sexo e morfotipos. Em um teste de progênies e procedências instalado em 1997, foram avaliadas em agosto de 2015 (dois anos após a última colheita) duas metodologias de análise visual. Para tanto, participaram cinco avaliadores treinados que determinaram, para cada planta, uma estimativa de biomassa comercial (kg), e uma nota, com base em um escore de produtividade (0-10). Para avaliação da produtividade pelas técnicas tradicionais, todas as plantas foram podadas e tiveram sua biomassa comercial (folhas e ramos finos menores de 7 mm de diâmetro) colhida e avaliada por meio de pesagem (Kg.planta-1). As avaliações foram realizadas em experimento instalado em blocos ao acaso, com cinco repetições, sete procedências e 126 progênies, totalizando 5292 plantas avaliadas. Os métodos avaliados foram eficientes na estimativa da biomassa comercial. Os avaliadores apresentaram boa acuidade nas estimativas, expressando de forma eficiente a maior produtividade determinada por comparação de médias entre as procedências, sexo das matrizes e morfotipos. As maiores correlações foram verificadas na análise geral das médias e a estimativa de biomassa comercial é a melhor metodologia para estimar a biomassa comercial aferida em plantas adultas de erva-mate.