Felipe Denardin Costa

A Simplified Model for Intermittent Turbulence in the Nocturnal Boundary Layer

A model for the exchange between the surface and the atmosphere under stable conditions is proposed. It is based on the classical scheme first suggested by Blackadar and comprises prognostic equations for the wind components and air and ground temperature. The main difference from previous works consists in the fact that the turbulent intensity is determined by a prognostic equation for turbulent kinetic energy (TKE), rather than by using stability functions that arbitrarily relate it to atmospheric stability. Results show that the model reproduces the condition of connection and disconnection between the surface and upper levels. Furthermore, it leads to periodic turbulence bursts when one level within the stable boundary layer (SBL) is considered and the use of additional levels increasingly leads to more complex solutions, characterizing the occurrence of global intermittency. Such turbulence bursts occur in the disconnected state and cause large fluctuations of the variables near the surface. The boundary layer height plays a role in the sense that for the same geostrophic winds, connection is favored for shallower layers. Although playing a role in the intermittency characteristics, soil type is not determinant to their existence, as the bursts occur even for very high values of heat capacity. Vertical profiles for both the intermittent and connected state are analyzed and in general agree with observations. It is shown that, near the surface, weak turbulence bursts favor the exchange between the air and the cooler ground, leading to a local temperature decrease, while stronger events that mix the air deeper in the SBL cause an average warming tendency. An opposite pattern occurs at the upper SBL. Intermittency is favored over a range of low geostrophic winds and clear skies, in agreement with previous suggestions. The vertical structure of the intermittent events is analyzed, and it shown that they are generated at the surface by a local shear increase above a threshold, propagating upward through the turbulence transfer term in the TKE equation. It is proposed that such events constitute a natural characteristic of the disconnected SBL, which occurs along with low large-scale winds and clear skies.

Influence of Val16Ala SOD2 polymorphism on the in-vitro effect of clomiphene citrate in oxidative metabolism

This study investigated the in-vitro antioxidant properties of the ovulation induction drug, clomiphene citrate, and assessed whether its effects are influenced by the Val16Ala polymorphism in the SOD2 gene, which encodes manganese superoxide dismutase enzyme. The investigation involved an in-vitro experimental protocol testing the effect of different concentrations of clomiphene citrate on antioxidant capacity, reactive oxygen species (ROS) production and peripheral blood mononuclear cell (PBMC) culture viability. A total of 58 healthy adult women were genotyped for the Val16Ala SOD2 polymorphism, and blood samples were collected to perform in-vitro experiments. ROS production and cytotoxicity assays were performed on blood and PBMC from carriers of different Val16Ala SOD2 genotypes. Clomiphene citrate exhibited antioxidant capacity and effects and decreased ROS production. The AA genotype displayed a more responsive antioxidant effect with clomiphene citrate treatment than other genotypes. AA and AV PBMC showed an increase in viability following treatment with 10 μmol/l clomiphene citrate when compared with control groups. The results suggest that clomiphene citrate exhibits antioxidant activity similar to that observed with other selective oestrogen receptor modulators, and the intensity of the effect appears to be SOD2 polymorphism dependent. This study was performed to investigate whether clomiphene citrate, a drug broadly used to evaluate reproductive function in women, presents antioxidant effects and if these effects could be influenced by genetic variation in the women. We found evidence that clomiphene citrate has some antioxidant properties similar to those observed with other selective oestrogen receptor modulators such as tamoxifen. As the antioxidant enzyme manganese superoxide dismutase (SOD2) is considered a key molecule involved in female reproductive metabolism, we also tested if a functional SOD2 gene polymorphism (Val16Ala) could influence the in-vitro antioxidant clomiphene citrate response. Significant differences of the clomiphene citrate antioxidant effect on PBMC with different Val16Ala SOD genotypes were observed in this study. Based on these results, we could speculate that alterations in SOD2 activity caused by the Val16Ala polymorphism can result in differential responses to drugs such as clomiphene citrate. In assisted reproduction clinics, clomiphene citrate is commonly used to induce ovulation, especially in patients with polycystic ovary syndrome. However, some women have clomiphene citrate resistance and either ovulation is not triggered by the drug or ovulation is induced but the pregnancy still fails. The causes of no effect of clomiphene citrate remain unclear and we cannot discard the influence of genetic effects including the Val16Ala SOD2 polymorphism. Therefore, it is important to perform complementary investigations considering the potential pharmacogenetic influence of Val16Ala SOD2 polymorphism on the treatment of polycystic ovary syndrome or in ovulation to elucidate this question.

The Influence of Submeso Processes on Stable Boundary Layer Similarity Relationships

AbstractPrevious observational studies in the stable boundary layer diverge appreciably on the values of dimensionless ratios between turbulence-related quantities and on their stability dependence. In the present study, the hypothesis that such variability is caused by the influence of locally dependent nonturbulent processes, referred to as submeso, is tested and confirmed. This is done using six datasets collected at sites with different surface coverage. The time-scale dependence of wind components and temperature fluctuations is presented using the multiresolution decomposition, which allows the identification of the turbulence and submeso contributions to spectra and cospectra. In the submeso range, the spectra of turbulence kinetic energy range increases exponentially with time scale. The exponent decreases with the magnitude of the turbulent fluctuations at a similar manner at all sites. This fact is used to determine the smaller time scale with relevant influence of submeso processes and a ratio ...

The Coupling State of an Idealized Stable Boundary Layer

The coupling state between the surface and the top of the stable boundary layer (SBL) is investigated using four different schemes to represent the turbulent exchange. An idealized SBL is assumed, with fixed wind speed and temperature at its top. At the surface, two cases are considered, first a constant temperature, 20 K lower than the SBL top, and later a constant 2 K h−1 cooling rate is assumed for 10 h after a neutral initial condition. The idealized conditions have been chosen to isolate the influence of the turbulence formulations on the coupling state, and the intense stratification has the purpose of enhancing such a response. The formulations compared are those that solve a prognostic equation for turbulent kinetic energy (TKE) and those that directly prescribe turbulence intensity as a function of atmospheric stability. Two TKE formulations are considered, with and without a dependence of the exchange coefficients on stability, while short and long tail stability functions (SFs) are also compared. In each case, the dependence on the wind speed at the SBL top is considered and it is shown that, for all formulations, the SBL experiences a transition from a decoupled state to a coupled state at an intermediate value of mechanical forcing. The vertical profiles of potential temperature, wind speed and turbulence intensity are shown as a function of the wind speed at the SBL top, both for the decoupled and coupled states. The formulation influence on the coupling state is analyzed and it is concluded that, in general, the simple TKE formulation has a better response, although it also tends to overestimate turbulent mixing. The consequences are discussed.

Influence of Val16Ala-SOD2 polymorphism on sperm quality parameters

Abstract The purpose of this study was to investigate the association between the Val16Ala superoxide dismutase manganese-dependent (SOD2) single nucleotide polymorphism (SNP) and sperm reproductive parameters in a sample of Brazilian men. A potential association between this polymorphism and some oxidative biochemical parameters as well as sperm plasma cell-free DNA (cfDNA) levels were also evaluated. The study was performed using semen samples obtained from male patients that had undergone semen analysis according to the 2010 World Health Organisation (WHO) recommendations and the Val16Ala-SOD2 SNP was genotyped by polymerase chain reaction (PCR). Oxidative parameters as well as cfDNA levels were spectrophotometrically and fluorimetrically determined. Statistical analysis included chi-square test, analysis of variance followed by Bonferroni post hoc test, as well as logistic regression multivariate analysis. Semen samples from 169 men (35.89 ± 7.33 years) were genotyped. The allelic frequencies were V= 0.485 (n = 97), A = 0.515 (n = 103), with statistically similar allelic frequencies to those of samples obtained from a general population: V = 0.509; A= 0.591. In general, AV samples presented lower numbers of sperm-altered parameters than homozygous sperm. Lipoperoxidation was higher in homozygous than heterozygous sperm samples. The results suggest that genetically caused S-HP imbalance could contribute to poor sperm quality and affect male fertility.

The Influence of the Intermittent Behavior of the Nocturnal Atmospheric Flow on the Prediction of the Diurnal Temperature Range: A Simplified Model Analysis

The variation of the atmospheric temperature near the surface associated with anthropogenic effects is analyzed using a simplified atmospheric model. Local changes in cloud cover and four different scenarios of atmospheric concentration of carbon dioxide are considered. The results show that the highest temperature variability occurs in the weak wind and decoupled state and in the transition between flow regimes. In agreement with previous efforts, the results indicate that the reduction of diurnal temperature range is related to the existence of two distinct flow regimes in the stable boundary layer. However, in the decoupled state, the occurrence of intermittent bursts of turbulence may cause temperature variations among the different scenarios to become unpredictable. It implies that it is difficult to predict the diurnal temperature range in places where low winds are common.

RELATIONSHIP BETWEEN WIND SPEED AND TURBULENT KINETIC ENERGY IN SIMPLIFIED MODELS OF NOCTURNAL BOUNDARY LAYER

The determination of the turbulent fluxes in very stable conditions is done, generally, through parameterizations. In this work the turbulent fluxes are estimated, by using a simplified model, through prognostic equations for the turbulent intensity, the sensible heat flux and the temperature variance. The results indicate that the model is able to reproduce both atmospheric coupling and the intermittent character of the turbulence in very stable conditions.

SIMULAÇÃO DOS GRANDES TURBILHÕES APLICADA AO CICLO DIÁRIO DA CAMADA LIMITE PLANETÁRIA - PARTE 1

In this work, some preliminary results on the ability of a largeeddy simulation model (LES) to describe the planetary boundary layerare presented. The performed simulation was initialized with verticalprofiles and surface data obtained experimentally and from a regionalmodel. Fally, the simulation results are compared with experimental datain order to verify the evolution of the simulated variables in relation tothe observed ones.