On the effects of circulation, sediment resuspension and biological incorporation by diatoms in an ocean model of aluminium, link to model data

The distribution of dissolved aluminium in the West Atlantic Ocean shows a mirror image with that of dissolved silicic acid, hinting at intricate interactions between the ocean cycling of Al and Si. The marine biogeochemistry of Al is of interest because of its potential impact on diatom opal remineralisation, hence Si availability. Furthermore, the dissolved Al concentration at the surface ocean has been used as a tracer for dust input, dust being the most important source of the bio-essential trace element iron to the ocean. Previously, the dissolved concentration of Al was simulated reasonably well with only a dust source, and scavenging by adsorption on settling biogenic debris as the only removal process. Here we explore the impacts of (i) a sediment source of Al in the Northern Hemisphere (especially north of ~ 40° N), (ii) the imposed velocity field, and (iii) biological incorporation of Al on the modelled Al distribution in the ocean. The sediment source clearly improves the model results, and using a different velocity field shows the importance of advection on the simulated Al distribution. Biological incorporation appears to be a potentially important removal process. However, conclusive independent data to constrain the Al / Si incorporation ratio by growing diatoms are missing. Therefore, this study does not provide a definitive answer to the question of the relative importance of Al removal by incorporation compared to removal by adsorptive scavenging.

Introducing non-linear analysis into sustained speech characterization to improve sleep apnea detection

We present a novel approach for detecting severe obstructive sleep apnea (OSA) cases by introducing non-linear analysis into sustained speech characterization. The proposed scheme was designed for providing additional information into our baseline system, built on top of state-of-the-art cepstral domain modeling techniques, aiming to improve accuracy rates. This new information is lightly correlated with our previous MFCC modeling of sustained speech and uncorrelated with the information in our continuous speech modeling scheme. Tests have been performed to evaluate the improvement for our detection task, based on sustained speech as well as combined with a continuous speech classifier, resulting in a 10% relative reduction in classification for the first and a 33% relative reduction for the fused scheme. Results encourage us to consider the existence of non-linear effects on OSA patients' voices, and to think about tools which could be used to improve short-time analysis.

Do currículo organizado ao currículo integrado: um potencial de aprendizagem vindo das dinâmicas transversais “Como desenvolver um processo de ensino e aprendizagem assente em dinâmicas transversais?”

Relatório de estágio para a obtenção do grau de mestre em Educação Pré-escolar e em Ensino do 1ciclo do Ensino Básico

Genetic fidelity under harsh conditions: Analysis of spontaneous mutation in the thermoacidophilic archaeon Sulfolobus acidocaldarius

Microbes whose genomes are encoded by DNA and for which adequate information is available display similar genomic mutation rates (average 0.0034 mutations per chromosome replication, range 0.0025 to 0.0046). However, this value currently is based on only a few well characterized microbes reproducing within a narrow range of environmental conditions. In particular, no genomic mutation rate has been determined either for a microbe whose natural growth conditions may extensively damage DNA or for any member of the archaea, a prokaryotic lineage deeply diverged from both bacteria and eukaryotes. Both of these conditions are met by the extreme thermoacidophile Sulfolobus acidocaldarius. We determined the genomic mutation rate for this species when growing at pH 3.5 and 75°C based on the rate of forward mutation at the pyrE gene and the nucleotide changes identified in 101 independent mutants. The observed value of about 0.0018 extends the range of DNA-based microbes with rates close to the standard rate simultaneously to an archaeon and to an extremophile whose cytoplasmic pH and normal growth temperature greatly accelerate the spontaneous decomposition of DNA. The mutations include base pair substitutions (BPSs) and additions and deletions of various sizes, but the S. acidocaldarius spectrum differs from those of other DNA-based organisms in being relatively poor in BPSs. The paucity of BPSs cannot yet be explained by known properties of DNA replication or repair enzymes of Sulfolobus spp. It suggests, however, that molecular evolution per genome replication may proceed more slowly in S. acidocaldarius than in other DNA-based organisms examined to date.

Dinâmica do fósforo no solo em função da adição de ácidos orgânicos de baixa massa molar

A baixa eficiência da adubação fosfatada em solos altamente intemperizados é devido, entre outros fatores, à adsorção do fósforo (P) à superfície das argilas silicatadas do tipo 1:1 e, principalmente, dos (hidr)óxidos de Fe e de Al. Manejos do solo que induzem a solubilização de formas de P indisponíveis para as plantas têm sido intensamente estudados nos últimos anos. Uma tentativa de aumentar a concentração de P disponível na solução do solo para sua absorção pelas plantas é a mobilização de P por ânions de ácidos orgânicos de baixa massa molar (AOBMM). Ânions derivados de AOBMM exsudados pelas raízes de plantas ou excretados por microrganismos são associados com algumas condições de rizosfera como deficiência de P e fitotoxidez de Al e interagem com o solo de forma a aumentar a biodisponibilidade de P. Dependendo dos atributos do solo, do grau de dissociação, das propriedades e do número de grupos carboxílicos dos ânions orgânicos, o P pode ser mobilizado do solo principalmente devido à dissolução complexométrica de minerais e à adsorção competitiva dos grupos funcionais carboxílicos e fosfato nos sítios de superfície coloidais. A capacidade dos ânions citrato, malato e oxalato em mobilizar P de amostras de um Neossolo Quartzarênico típico (RQ) e de um Latossolo Vermelho ácrico (LVwf) foi avaliada por meio de um estudo de lixiviação de ânions em colunas. Devido a não detecção de P nos efluentes das colunas com LVwf, foi realizado outro estudo em colunas, no qual somente citrato foi lixiviado, mas num volume maior, e as alterações das formas de P nas amostras desse solo induzidas pela lixiviação de citrato foram identificadas por espectroscopia de absorção de raios-X na borda K do fósforo (X-ray absorption near edge structure -XANES - spectroscopy). A capacidade dos ânions de AOBMM em solubilizar P foi mais dependente do teor de P disponível e de outros atributos do solo que do número de grupos funcionais carboxílicos dos ânions orgânicos. Somente o oxalato mobilizou P do RQ, enquanto todos os ânions de AOBMM foram capazes de mobilizar P do LVwf. Quando baixos volumes de solução contendo ânions de AOBMM foram lixiviados no solo, além do aumento do pH, a mobilização de P foi acompanhada pela mobilização de Al no RQ (pH água = 5), e pela mobilização de Ca no LVwf (pH água = 5.6), o que indica solubilização de P pela complexação de Al, Ca, ou Fe, de fosfatos insolúveis, ou pela inibição da precipitação de P com esses metais. Ao lixiviar um volume maior de citrato no LVwf, o P também não foi detectado nos efluentes das colunas, mas houve lixiviação intensa de Al e Fe, bem como mudanças nas proporções de formas de P no solo caracterizadas pelos espectros XANES. Embora tenhamos encontrado indícios da ação dos principais mecanismos de solubilização de P (dissolução complexométrica de minerais e troca de ligantes entre grupos funcionais carboxílicos e P adsorvido ao solo), os ânions de AOBMM mostraram pouco potencial de efetivamente aumentar a biodisponibilidade de P.

Theory of ferromagnetism in planar heterostructures of (Mn,III)-V semiconductors

A density-functional theory of ferromagnetism in heterostructures of compound semiconductors doped with magnetic impurities is presented. The variable functions in the density-functional theory are the charge and spin densities of the itinerant carriers and the charge and localized spins of the impurities. The theory is applied to study the Curie temperature of planar heterostructures of III-V semiconductors doped with manganese atoms. The mean-field, virtual-crystal and effective-mass approximations are adopted to calculate the electronic structure, including the spin-orbit interaction, and the magnetic susceptibilities, leading to the Curie temperature. By means of these results, we attempt to understand the observed dependence of the Curie temperature of planar δ-doped ferromagnetic structures on variation of their properties. We predict a large increase of the Curie temperature by additional confinement of the holes in a δ-doped layer of Mn by a quantum well.

Do currículo organizado ao currículo integrado: um potencial de aprendizagem vindo das dinâmicas transversais “Como desenvolver um processo de ensino e aprendizagem assente em dinâmicas transversais?”

Relatório de estágio para a obtenção do grau de mestre em Educação Pré-escolar e em Ensino do 1ciclo do Ensino Básico

Seasonal changes in sediment core PS1795-2

The Weddell Sea and the associated Filchner-Rønne Ice Shelf constitute key regions for global bottomwater production today. However, little is known about bottom-water production under different climate and icesheet conditions. Therefore, we studied core PS1795, which consists primarily of fine-grained siliciclastic varves that were deposited on contourite ridges in the southeastern Weddell Sea during the Last Glacial Maximum (LGM). We conducted high-resolution X-ray fluorescence (XRF) analysis and grain-size measurements with the RADIUS tool (Seelos and Sirocko, 2005, doi:10.1111/j.1365-3091.2005.00715.x) using thin sections to characterize the two seasonal components of the varves at sub-mm resolution to distinguish the seasonal components of the varves. Bright layers contain coarser grains that can mainly be identified as quartz in the medium-to-coarse silt grain size. They also contain higher amounts of Si, Zr, Ca, and Sr, as well as more ice-rafted debris (IRD). Dark layers, on the other hand, contain finer particles such as mica and clay minerals from the chlorite and illite groups. In addition, Fe, Ti, Rb, and K are elevated. Based on these findings as well as on previous analyses on neighbouring cores, we propose a model of enhanced thermohaline convection in front of a grounded ice sheet that is supported by seasonally variable coastal polynya activity during the LGM. Accordingly, katabatic (i.e. offshore blowing) winds removed sea ice from the ice edge, leading to coastal polynya formation. We suggest that glacial processes were similar to today with stronger katabatic winds and enhanced coastal polynya activity during the winter season. Under these conditions, lighter coarser-grained layers are likely glacial winter deposits, when brine rejection was increased, leading to enhanced bottom-water formation and increased sediment transport. Vice versa, darker finer-grained layers were then deposited during less windier season, mainly during summer, when coastal polynya activity was likely reduced.

(Table 1) Element concentrations in detrital sediments of ODP Site 184-1148

The chemical index of alteration (CIA) and elemental ratios that are sensitive to chemical weathering, such as Ca/Ti, Na/Ti, Al/Ti, Al/Na, Al/K, and La/Sm, were analyzed for detrital sediments at Ocean Drilling Program Site 1148 from the northern South China Sea to reveal information of chemical weathering in the source regions during the early Miocene. High CIA values of ~80, coupled with high Al/Ti and Al/Na and low Na/Ti and Ca/Ti, are observed for the sediments at ~23 Ma, indicating a high chemical weathering intensity in the north source region, i.e., south China. This was followed by gradual decreases in Al/Ti, Al/Na, La/Sm, and Al/K ratios, as well as the CIA values, and increases in Ca/Ti and Na/Ti ratios. These records together with other paleoclimate proxies, such as black carbon d13C and benthic foraminifer d18O, give reliable information on the climate changes in south China. Our results show that the climate in south China was warm and humid in the early Miocene (~23 Ma) according to the chemical weathering records. The humidity in south China decreased from the early Miocene to Present with several fluctuations centering at approximately 15.7 Ma, 8.4 Ma, and 2.5 Ma, coincident with the global cooling since the middle Miocene. These climate changes implied that the summer east Asian monsoon has dramatically affected south China in the early Miocene, whereas the influence of the summer monsoon on this region has decreased continuously since that time, probably because of the intensification of the winter monsoon. Such an evolution for the east Asian monsoon is different from that for the Indian monsoon.

Rashba spin precession in a magnetic field

Spin precession due to Rashba spin-orbit coupling in a two-dimension electron gas is the basis for the spin field effect transistor, in which the overall perfect spin-polarized current modulation could be acquired. There is a prerequisite, however, that a strong transverse confinement potential should be imposed on the electron gas or the width of the confined quantum well must be narrow. We propose relieving this rather strict limitation by applying an external magnetic field perpendicular to the plane of the electron gas because the effect of the magnetic field on the conductance of the system is equivalent to the enhancement of the lateral confining potential. Our results show that the applied magnetic field has little effect on the spin precession length or period although in this case Rashba spin-orbit coupling could lead to a Zeeman-type spin splitting of the energy band.

Extending a model of shift-work tolerance

The present study contributes to theory and practice through the development of a model of shift-work tolerance with the potential to indicate interventions that reduce nurses' intention toward turnover and increase job satisfaction in hospital-based settings. Survey data from 1257 nurses were used to conduct structural equation modeling that examine the direct and indirect effects of supervisor and colleague support, team identity, team climate, and control over working environment on time-based work/life conflict, psychological well-being, physical symptoms, job satisfaction, and turnover intention. The analysis of the proposed model revealed a good fit The chi-square difference test was non-significant (χ2(26)=338.56), the fit indices were high (CFI=.923, NFI=.918, and NNFI=.868), the distribution of residuals was symmetric and approached zero, the average standardized residual was low (AASR=.04), and the standardized RMR was .072. In terms of the predictor variable, the final model explained 48% of the variance in turnover intention. The data revealed considerable evidence of both direct effects on adjustment and complex indirect links between levels of adjustment and work-related social support, team identity, team climate, and control. Nurses with high supervisor and coworker support experienced more positive team climates, identified more strongly with their team, and increased their perceptions of control over their work environment. This in turn lowered their appraisals of their time-based work/life conflict, which consequently increased their psychological well-being and job satisfaction and reduced their physical health symptoms and turnover intention. The type of shift schedule worked by the nurses influenced levels of turnover intention, control over work environment, time-based work/life conflict, and physical symptoms.

Mutation analysis to verify feature matrices for isolating errors in simulation models

Software simulation models are computer programs that need to be verified and debugged like any other software. In previous work, a method for error isolation in simulation models has been proposed. The method relies on a set of feature matrices that can be used to determine which part of the model implementation is responsible for deviations in the output of the model. Currrently these feature matrices have to be generated by hand from the model implementation, which is a tedious and error-prone task. In this paper, a method based on mutation analysis, as well as prototype tool support for the verification of the manually generated feature matrices is presented. The application of the method and tool to a model for wastewater treatment shows that the feature matrices can be verified effectively using a minimal number of mutants.

Spectrally-controlled, gain-switched operation of InGaN diode laser

Self-seeded, gain-switched operation of an InGaN multi-quantum-well diode laser is reported for the first time. Narrow-line, wavelength-tunable, picosecond pulses have been generated from a standard, uncoated diode laser with an external feedback.

Pulse tail suppression in laser diode output by tunable notch filter

Efficient suppression of relaxation oscillations in the output signal from an overdriven gain-switched laser diode was demonstrated. Several quantum-well distributed feedback laser diodes from different manufacturers were used for experimental analysis. A five-fold increase in the peak power was achieved for the tail-free operation. It was found that spectral filtering removed the nonlinearly chirped components resulting in pulse shortening by a factor of three.

Self-training from labeled features for sentiment analysis

Sentiment analysis concerns about automatically identifying sentiment or opinion expressed in a given piece of text. Most prior work either use prior lexical knowledge defined as sentiment polarity of words or view the task as a text classification problem and rely on labeled corpora to train a sentiment classifier. While lexicon-based approaches do not adapt well to different domains, corpus-based approaches require expensive manual annotation effort. In this paper, we propose a novel framework where an initial classifier is learned by incorporating prior information extracted from an existing sentiment lexicon with preferences on expectations of sentiment labels of those lexicon words being expressed using generalized expectation criteria. Documents classified with high confidence are then used as pseudo-labeled examples for automatical domain-specific feature acquisition. The word-class distributions of such self-learned features are estimated from the pseudo-labeled examples and are used to train another classifier by constraining the model's predictions on unlabeled instances. Experiments on both the movie-review data and the multi-domain sentiment dataset show that our approach attains comparable or better performance than existing weakly-supervised sentiment classification methods despite using no labeled documents.