Absolute Density Research Articles

Measurements of atoms and metastable species in N2 and H2–N2 nanosecond pulse plasmas

Time-resolved, absolute number densities of metastable N2(A3Σ u +, v = 0, 1) molecules, ground state N2 and H atoms, and rotational–translational temperature have been measured by tunable diode laser absorption spectroscopy and two-photon absorption laser-induced fluorescence in diffuse N2 and N2–H2 plasmas during and after a nanosecond pulse discharge burst. Comparison of the measurement results with the kinetic modeling predictions, specifically the significant reduction of the N2(A3Σ u +) populations and the rate of N atom generation during the burst, suggests that these two trends are related. The slow N atom decay in the afterglow, on a time scale longer than the discharge burst, demonstrates that the latter trend is not affected by N atom recombination, diffusion to the walls, or convection with the flow. This leads to the conclusion that the energy pooling in collisions of N2(A3Σ u +) molecules is a major channel of N2 dissociation in electric discharges where a significant fraction of the input energy goes to electronic excitation of N2. Additional measurements in a 1% H2–N2 mixture demonstrate a further significant reduction of N2(A3Σ u +, v = 0, 1) populations, due to the rapid quenching by H atoms accumulating in the plasma. Comparison with the modeling predictions suggests that the N2(A3Σ u +) molecules may be initially formed in the highly vibrationally excited states. The reduction of the N2(A3Σ u +) number density also diminishes the contribution of the energy pooling process into N2 dissociation, thus reducing the N atom number density. The rate of N atom generation during the burst also decreases, due to its strong coupling to N2(A3Σ u +, v) populations. On the other hand, the rate of H atom generation, produced predominantly by the dissociative quenching of the excited electronic states of N2 by H2, remains about the same during the burst, resulting in a nearly linear rise in the H atom number density. Comparison of the kinetic model predictions with the experimental results suggests that the yield of H atoms during the quenching of the excited electronic state of N2 by molecular H2 is significantly less than 100%. The present results quantify the yield of N and H atoms in high-pressure H2–N2 plasmas, which have significant potential for ammonia generation using plasma-assisted catalysis.

Characterization of ZnO/nanofluid for improving heat transfer in thermal systems

Nanofluids are currently regarded a new growing area of research with numerous advantages over conventional heat transport fluids in heat transfer applications. Because, nanofluids possess a better thermo-physical characteristics. Hence, they can perform better when compared to traditional working fluids. The thermo-physical characteristics of zinc oxide nanoparticles disbanded water (ZnO/water) nanofluid was evaluated in this study by altering the volume proportions of nano-ZnO particles and temperature experimentally. The volume proportion of ZnO/water nanofluids was adjusted from 0.01 to 0.2 in four different (0.01, 0.05, 0.1 and 0.2) fractions. Using a field emission scanning electron microscope, the surface properties of ZnO nanoparticles were investigated. The results evidenced that the absolute viscosity, thermal conductivity, and density of the water was augmented by 1.43%, 37.0%, and 1.57%, respectively through the diffusion of 0.2 vol% of nano-ZnO particles in water. In contrast, the specific heat of water was lessened by 2.7% with 0.2 vol% of nano-ZnO particles in water.

Quantitative fs-TALIF in high-pressure NRP discharges: calibration using VUV absorption spectroscopy

This work presents a femtosecond two-photon absorption laser-induced fluorescence (fs-TALIF) diagnostic for measuring ground-state atomic nitrogen in nanosecond repetitively pulsed (NRP) discharges. Absolute atom density is obtained from the TALIF signal via a novel calibration technique based on one-photon direct absorption measurements performed in a low-pressure DC discharge. The Vacuum Ultraviolet (VUV) measurements were done at the Soleil synchrotron facility using the high-resolution Fourier-transform spectrometer (minimum linewidth Δ = 0.08 cm−1). The main goal of this work was to develop a quench-free diagnostic technique, which would allow measurements at elevated pressures with high spatial and temporal resolution. Here fs-TALIF measurements of N(4S) are demonstrated in the NRP post-discharge between 1–500 μs after the nanosecond high-voltage pulse. A maximum number density of N-atoms of 5 × 1016 cm−3 was measured at 1 μs after the pulse when the discharge was operated at 1 bar in pure nitrogen. This corresponds to a dissociation fraction of ∼0.1%. The fs-TALIF technique at high laser intensity regime (>1 TW cm−2) calibrated using VUV absorption was compared with the fs-TALIF at low laser intensity regime (<100 MW cm−2) calibrated via the well-established non-saturated TALIF technique using krypton as an etalon gas. It was found that the two measurements of N(4S) in the NRP post-discharge agree within a factor of 3. Importantly, the limit of detection of the fs-TALIF at high laser intensity regime was determined to be . This is approximately one order of magnitude better than previously reported by ns-TALIF in low-pressure discharges.

Sodium and Potassium Intake, the Sodium to Potassium Ratio, and Associated Characteristics in Older Adults, NHANES 2011-2016.

Sodium, potassium, and the balance between these 2 nutrients are associated with hypertension and cardiovascular disease, and prevalence of these conditions increases with age. However, limited information is available on these intakes among older adults. Our aim was to explore the socioeconomic and health factors associated with usual sodium and potassium intakes and the sodium to potassium (Na:K) ratio of older adults. This was a cross-sectional, secondary analysis of the 2011-2012, 2013-2014, and 2015-2016 National Health and Nutrition Examination Survey. This study included the data of 5,104 adults 50 years and older, with at least one reliable 24-hour dietary recall and an estimated glomerular filtration rate ≥60 mL/min/1.73 m2. Sodium and potassium intake, as absolute intake, density (per 1,000 kcal) and ratio of Na:K intake. We used t tests and χ2 tests to examine significant differences in intakes on a given day by characteristics. Linear and logistic regression models were used to assess associations of socioeconomic and health characteristics with usual sodium and potassium intakes, determined using the National Cancer Institute method. Only 26.2% of participants consumed <2,300 mg sodium (16.2% of men and 35.2% of women) and 36.0% of men and 38.1% of women consumed at least 3,400 mg and 2,600 mg of potassium, respectively. Fewer than one-third of participants consumed a Na:K ratio of <1.0. Women, those with lower blood pressure, and those with a lower body mass index were more likely to have a ratio <1.0. Participants consumed too much sodium and not enough potassium, based on current recommendations. A higher Na:K ratio was significantly associated with established risk factors for cardiovascular disease. The study findings suggest that more research on cardiovascular health should include both sodium and potassium, as well as balance between these nutrients.

Dual-capillary dilatometer for density measurements of supercooled water

An apparatus tailored to accurate density measurements of supercooled water, i.e. liquid water in a metastable state below the freezing point temperature, was recently developed at the Institute of Thermomechanics of the Czech Academy of Sciences. The apparatus, dual-capillary dilatometer, is described, together with the measurement procedure and the evaluation methodology. The primary result of the dual-capillary method are relative densities with respect to the density at a reference temperature and given pressure. In order to calculate absolute densities, densities at the reference temperature as a function of pressure are needed. For calculation of such pressure dependence of density, so called thermodynamic integration involving literature thermodynamic data and our experimental results is used. The dual-capillary dilatometer was successfully employed in density measurements of ordinary water, heavy water and seawater. The data in the temperature range from 238.15 to 303.15 K at pressures from atmospheric up to 200 MPa are presented and compared with respective IAPWS formulations of thermodynamic properties. The data for ordinary water are also compared with an accurate equation of state for supercooled water of Holten et al. (2014) revealing good mutual agreement. The expanded uncertainty of relative densities acquired by means of the dual-capillary method is estimated to be lower than 50 ppm.

Cautious considerations for using multiple covariate distance sampling and seafloor terrain for improved estimates of rockfish density

Distance sampling is one of the most widely used methods for adjusting fish counts for detectability, which allows the estimation of absolute density. Further, abundance can be estimated spatially beyond the transect width with density surface models. The present study used a density surface modelling approach with survey data from line transects and terrain metrics from multibeam acoustic bathymetry data, integrated with a Geographic Information System, to estimate the population density of Pacific Ocean perchSebastes alutus(POP) within 6 sampling areas in the Gulf of Alaska (GOA) at 2 sampling scales: local and landscape. For adult POP, the final density model included depth as a significant predictor for density estimation at both the local and landscape scale. Additional factors included sponge coverage (local scale), aspect eastness and seafloor slope (landscape scale). Predicted densities of adult POP are highest on low (&lt;5°) eastern-facing slopes with high sponge coverage (&gt;75%), at depths of 100 to 200 m. By using habitat-based density models with data collected from line transect distance sampling and multibeam acoustic seafloor mapping surveys, we provide an alternative method for estimating rockfish abundance in untrawlable areas, which may help improve rockfish stock assessments and essential fish habitat descriptions and maps.

Ubim Fiber (Geonoma baculífera): A Less Known Brazilian Amazon Natural Fiber for Engineering Applications

The production of synthetic materials generally uses non-renewable forms of energy, which are highly polluting. This is driving the search for natural materials that offer properties similar to synthetic ones. In particular, the use of natural lignocellulosic fibers (NLFs) has been investigated since the end of 20th century, and is emerging strongly as an alternative to replace synthetic components and reinforce composite materials for engineering applications. NLFs stand out in general as they are biodegradable, non-polluting, have comparatively less CO2 emission and are more economically viable. Furthermore, they are lighter and cheaper than synthetic fibers, and are a possible replacement as composite reinforcement with similar mechanical properties. In the present work, a less known NLF from the Amazon region, the ubim fiber (Geonoma bacculifera), was for the first time physically characterized by X-ray diffraction (XRD). Fiber density was statistically analyzed by the Weibull method. Using both the geometric method and the Archimedes’ technique, it was found that ubim fiber has one of the lowest densities, 0.70–0.73 g/cm3, for NLFs already reported in the literature. Excluding the porosity, however, the absolute density measured by pycnometry was relatively higher. In addition, the crystallinity index, of 83%, microfibril angle, of 7.42–7.49°, and ubim fiber microstructure of lumen and channel pores were also characterized by scanning electron microscopy. These preliminary results indicate a promising application of ubim fiber as eco-friendly reinforcement of civil construction composite material.

Biodiversity and Community Analysis of Plant-Parasitic and Free-Living Nematodes Associated with Maize and Other Rotational Crops from Punjab, Pakistan.

Maize (Zea mays L.) is one of Pakistan’s essential staple food crops. Plant-parasitic nematodes (PPNs) are a significant restraint in maize production. However, free-living nematodes (FLNs) provide crucial ecological functions such as suppressing pests and nutrient mineralization. This study aimed to assess the community analysis of plant-parasitic and free-living nematodes associated with maize and other rotational crops (those cultivated in sequence with the maize in the same field) from Punjab, Pakistan. The occurrence percentage was observed per 500 g soil for each nematode genus. The present study revealed that 24 species of plant-parasitic and free-living nematodes were identified from maize crops and other rotational crops from 16 localities through Punjab, Pakistan. Nematode communities were analyzed by absolute frequency, relative frequency, relative density, and prominence value, while cluster analysis was based on the presence or absence of nematode in different localities. The overall proportion of plant-parasitic nematodes was 35%, while free-living soil nematodes recovered 65%, out of 210 samples of maize and other rotational crops. Several major genera of plant-parasitic nematodes were reported during the present study viz., Ditylenchus, Filenchus, Helicotylenchus, Hemicriconemoides, Heterodera, Hoplolaimus, Malenchus, Pratylenchus, Psilenchus, Rotylenchulus, Seinura, Telotylenchus, Tylenchorhynchus, and Xiphinema Community relationship revealed the overall dominance of Heterodera zeae, with the highest incidence (55.71%) followed by Tylenchorhynchus elegans (33.33%) and Helicotylenchus certus (24.76%). The results provide valuable information on the community structure of nematodes in maize and other rotational crops of maize in Punjab, Pakistan. Moreover, this data can be used as a preventive measure before PPN incidence results in greater losses on maize.

Evidence of the dominant production mechanism of ammonia in a hydrogen plasma with parts per million of nitrogen

Absolute ground state atomic hydrogen densities were measured, by the utilization of two-photon absorption laser induced fluorescence, in a low-pressure electron cyclotron resonance plasma as a function of nitrogen admixtures—0 to 5000 ppm. At nitrogen admixtures of 1500 ppm and higher, the spectral distribution of the fluorescence changes from a single Gaussian to a double Gaussian distribution; this is due to a separate, nascent contribution arising from the photolysis of an ammonia molecule. At nitrogen admixtures of 5000 ppm, the nascent contribution becomes the dominant contribution at all investigated pressures. Thermal loading experiments were conducted by heating the chamber walls to different temperatures; this showed a decrease in the nascent contributions with increasing temperature. This is explained by considering how the temperature influences recombination coefficients, and from which, it can be stated that the Langmuir–Hinshelwood recombination mechanism is dominant over the Eley–Rideal mechanism.

Adsorption and diffusion behavior of CO2/H2 mixture in calcite slit pores: A molecular simulation study

The adsorption and diffusion of gases in porous media are fundamental phenomena that find widespread application in the energy and chemical industries. In this study, we used Grand Canonical Monte Carlo and molecular dynamics simulation methods to evaluate the adsorption and diffusion properties of CO2 and H2 in the calcite silt-like pores. We report the influence of pressure, pore size, and temperature on adsorption isotherms (i.e., total, absolute, and excess) and diffusion coefficients (i.e., self-diffusion, Fick transport diffusion, and Maxwell-Stefan diffusion). The results reveal a greater CO2 adsorption capacity compared to H2 and the easy absorption of the oxygen atoms of CO2 onto the surface of calcite. The adsorption capacities of CO2 and H2 increased together with the pressure, and the pore size had little effect on the absolute adsorption capacity and density distribution of the pure compounds. The interaction energy between calcite and CO2/H2 showed that the calcite had greater affinity for CO2 than for H2. The CO2 diffusion coefficients were smaller than those of H2. The diffusion coefficients of CO2 and the mutual diffusion coefficients of the gas mixture increased with increasing pressure before stabilizing. In contrast, the diffusion coefficients of H2 decreased with an increase in pressure.

Ion current rectification in asymmetric charged bilayer nanochannels

At present, little attention has been paid to the ion current rectification (ICR) performance in the bilayer nanochannel with non-uniform charge distribution, which has the similar asymmetrical property with the conical nanochannel. In this work, we have established the ions transport model in the bilayer nanochannel with the coupled Poisson-Nernst-Planck (PNP) equations. Four configuration types bilayer nanochannel are compared on the ion rectification performance. The results show that asymmetrical geometry without the surface charge cannot induce ICR and the existence of surface charge is necessary. Besides, the config.3 has the best ICR performance and the physical mechanisms are discussed in detail. It is found that the ICR performance can be enhanced by regulating the surface charge density, geometry parameters and ion concentration. The ICR ratio increases as the absolute surface charge density increases and the effect is more significant to the change of left nanopore. When the total length of the bilayer nanochannel is fixed, the ICR ratio increases first and then decreases with the increasing length of the left nanopore. In addition, the forward current is more sensitive to the change of diameter of left nanopore and the reverse current is more sensitive to the change of diameter of right nanopore. When the bulk concentration varies, the ICR ratio decreases with the increasing concentration. The research results provide useful information for ions transport control and optimization of micro/nano fluidic devices.

Intravenous and Intramuscular Allopregnanolone for Early Treatment of Status Epilepticus: Pharmacokinetics, Pharmacodynamics, and Safety in Dogs.

Allopregnanolone (ALLO) is a neurosteroid that modulates synaptic and extrasynaptic GABAA receptors. We hypothesize that ALLO may be useful as first-line treatment of status epilepticus (SE). Our objectives were to (1) characterize ALLO pharmacokinetics-pharmacodynamics PK-PD after intravenous (IV) and intramuscular (IM) administration and (2) compare IV and IM ALLO safety and tolerability. Three healthy dogs and two with a history of epilepsy were used. Single ALLO IV doses ranging from 1-6 mg/kg were infused over 5 minutes or injected IM. Blood samples, vital signs, and sedation assessment were collected up to 8 hours postdose. Intracranial EEG (iEEG) was continuously recorded in one dog. IV ALLO exhibited dose-proportional increases in exposure, which were associated with an increase in absolute power spectral density in all iEEG frequency bands. This relationship was best described by an indirect link PK-PD model where concentration-response was described by a sigmoidal maximum response (Emax) equation. Adverse events included site injection pain with higher IM volumes and ataxia and sedation associated with higher doses. IM administration exhibited incomplete absorption and volume-dependent bioavailability. Robust iEEG changes after IM administration were not observed. Based on PK-PD simulations, a 2 mg/kg dose infused over 5 minutes is predicted to achieve plasma concentrations above the EC50, but below those associated with heavy sedation. This study demonstrates that ALLO is safe and well tolerated when administered at 1-4 mg/kg IV and up to 2 mg/kg IM. The rapid onset of effect after IV infusion suggests that ALLO may be useful in the early treatment of SE. SIGNIFICANCE STATEMENT: The characterization of the pharmacokinetics and pharmacodynamics of allopregnanolone is essential in order to design clinical studies evaluating its effectiveness as an early treatment for status epilepticus in dogs and people. This study has proposed a target dose/therapeutic range for a clinical trial in canine status epilepticus.

A Multicomponent Magnetic Proxy for Solar Activity

AbstractWe present a new, multicomponent magnetic proxy for solar activity derived from full disk magnetograms that can be used in the specification and forecasting of the Sun’s radiative output. To compute this proxy we project Carrington maps, such as the synchronic Carrington maps computed with the Advective Flux Transport (AFT) surface flux transport model, to heliographic cartesian coordinates and determine the total unsigned flux as a function of absolute magnetic flux density. Performing this calculation for each day produces an array of time series, one for each flux density interval. Since many of these time series are strongly correlated, we use principal component analysis to reduce them to a smaller number of uncorrelated time series. We show that the first few principal components accurately reproduce widely used proxies for solar activity, such the the 10.7 cm radio flux and the Mg core‐to‐wing ratio. This suggests that these magnetic time series can be used as a proxy for irradiance variability for emission formed over a wide range of temperatures.

Properties of the C ii 1334 Å Line in Coronal Hole and Quiet Sun as Observed by IRIS

Abstract Coronal holes (CHs) have subdued intensity and net blueshifts when compared to the quiet Sun (QS) at coronal temperatures. At transition region temperatures, such differences are obtained for regions with identical absolute photospheric magnetic flux density (∣B∣). In this work, we use spectroscopic measurements of the C ii 1334 Å line from the Interface Region Imaging Spectrograph, formed at chromospheric temperatures, to investigate the intensity, Doppler shift, line width, skew, and excess kurtosis variations with ∣B∣. We find the intensity, Doppler shift, and linewidths to increase with ∣B∣ for CHs and QS. The CHs show deficit in intensity and excess total widths over QS for regions with identical ∣B∣. For pixels with only upflows, CHs show excess upflows over QS, while for pixels with only downflows, CHs show excess downflows over QS that cease to exist at ∣B∣ ≤ 40. Finally, the spectral profiles are found to be more skewed and flatter than a Gaussian, with no difference between CHs and QS. These results are important in understanding the heating of the atmosphere in CH and QS, including solar wind formation, and provide further constraints on the modeling of the solar atmosphere.

How to Count Bugs: A Method to Estimate the Most Probable Absolute Population Density and Its Statistical Bounds from a Single Trap Catch.

Simple SummaryThe importance of conservation and pest management programs cannot be overstated as climate change, loss of biodiversity, and biological invasions are on the rise. Such programs often rely on traps for population detection and monitoring, assigning management and conservation tactics, and evaluating treatment efficacies. In this paper, we propose a universal method for any insect trap system to estimate the most probable absolute population density and its statistical bounds from a single trap catch. This approach will help take insect detection and monitoring to a new, rigorously quantitative level.Knowledge of insect population density is crucial for establishing management and conservation tactics and evaluating treatment efficacies. Here, we propose a simple and universal method for estimating the most probable absolute population density and its statistical bounds. The method is based on a novel relationship between experimentally measurable characteristics of insect trap systems and the probability to catch an insect located a given distance away from the trap. The generality of the proposed relationship is tested using 10 distinct trapping datasets collected for insects from 5 different orders and using major trapping methods, i.e., chemical-baited traps and light. For all datasets, the relationship faithfully ( describes the experiment. The proposed approach will take insect detection and monitoring to a new, rigorously quantitative level. It will improve conservation and management, while driv-ing future basic and applied research in population and chemical ecology.

Elevation of runaway electron current by electron cyclotron resonance heating during disruptions on J-TEXT

Runaway electrons represent a serious problem for the reliable operation of future tokamaks. Radio frequency (RF) auxiliary heating can help suppress runaway electrons in the flat-top phase through a reduction in loop voltage. However, if a disruption occurs during RF auxiliary heating, it may lead to an increase in the runaway electron production due to the generation of a suprathermal population with energies in the order of ∼100 keV. The elevation of runaway current during disruptions by electron cyclotron resonance heating (ECRH) has been investigated on the J-TEXT tokamak. The results show that the conversion efficiency of runaway current increases with increased ECRH power. When the applied ECRH power is at the level of 400 kW, the conversion efficiency of Ohmic to runaway current increases from 35% to 75%, the thermal quench duration is decreased from 0.24 ms to 0.11 ms, and the Absolute Extreme Ultraviolet Spectrometer (AXUV) radiative power and electron density are about two times higher than the cases without ECRH heating.

Assembly method in GIS INTEGRO and its usage for solving of gravitational inverse problem

Various methods based on growing bodies are lately gaining attention in a context of inverse gravity problem that we call a family of “assembly methods”. A variant of method was adopted for GIS INTEGRO in original formulation that is fit for the problem of multiple bodies incorporated in an environment of varying density, in absolute densities (not density contrasts) that are however have to be a priori specified. Such formulation allowed the implementation of the method that is suitable for territory modeling in the regional scale. To workaround method’s instability a number of changes are proposed that consist of introduction of priority on atomic modifications, modification queue and assessment of model evolution instead of just the final result. The developed software allows processing of large grids (tens of millions of tiling elements) even on 5–8 year old desktops. Based on method approbation experience some insights and practice methods are presented. An application example is presented as part of work on modeling of Enisei-Khatanga regional depression territory.

Performance and Nanostructure Simulation of Phosphogypsum Modified by Sodium Carbonate and Alum.

This paper presents a new modification of the nanostructure of CaSO4·2H2O crystals containing nanopores. This nanoporous structure was achieved in phosphogypsum samples that were modified by sodium carbonate and alum. The effects of sodium carbonate and alum on the properties of phosphogypsum were studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods were used to explore the micro-mechanism of the composite system. Subsequently, molecular dynamics simulations were used to study the nanopore structures of the modified CaSO4·2H2O. The results show that the addition of sodium carbonate and alum reduced the absolute dry density by 23.1% compared with the original phosphogypsum sample, with a bending strength of 2.1 MPa and compressive strength of 7.5 MPa. In addition, new hydration products, sodium sulfate and sodium aluminum sulfate, were formed in the sample doped with sodium carbonate and alum. A new nanostructure of CaSO4·2H2O crystal containing nanopores was formed. Molecular simulations show that the hydration products were responsible for the surface nanopore formation, which was the main factor leading to an increase in mechanical strength. The presented nanopore structure yields lightweight and high strength properties in the modified phosphogypsum.

Ion fluxes and memory effects in an Ar–O2 modulated radiofrequency-driven atmospheric pressure plasma jet

In this work we used molecular beam mass spectrometry to characterize ion fluxes produced by a modulated radiofrequency (RF)-driven atmospheric pressure plasma jet operating in a homogeneous gas environment (Ar + 1% O2). The influence of the RF modulation frequency (100 Hz to 20 kHz) on the ion fluxes was investigated by time-resolved measurements, and the lifetimes of the dominant ions, O2 +, NO+, O−, O2 − and O3 −, were found to be 28 ± 2, 117 ± 8, 7.3 ± 0.4, 17 ± 1 and 23 ± 2 μs, respectively. The absolute ion densities in the near afterglow region were found to be of the order of 1011 cm−3. Significant differences in the dynamics of the positive and negative ions were found; these are explained by the presence of electrons at similar densities in the afterglow produced by electron detachment reactions from negative ions due to the large concentrations of atomic oxygen and singlet delta oxygen. Transitions in ion flux dynamics for different modulation frequencies and at the startup of the plasma were analyzed together with intensified charge coupled device images recording the plasma propagation in order to assess the dynamics of plasma plume propagation and how it is impacted by ‘memory effects’. Quantitative measurements of the ion densities enabling these memory effects are reported. The results in this paper highlight the tremendous impact of memory effects on plasma propagation and the corresponding pre-ionization.

Phytosociological survey of weed plants and their pasture control

Weeds damage economically interesting crop development, resulting in potential production loss of such crop. Thus, this study had de objective of surveying weeds’ phytosociology in Brachiaria brizantha (cv. Marandu) pasture and of evaluating the effectiveness of herbicides in mixtures on weeds control. The field studied has been using B. brizantha pasture for more than 10 years, divided in 4 areas with 1 ha each. After the first weeds harvest and identification, a mixture of Aminopyralid (50 g L-1) + Picloram (100 g L-1) + Triclopyr (150 g L-1) 1 L ha-1 + 1.5 L ha-1 of 2,4-D (2.5 L ha-1), Aminopyralid (50 g L-1) + Picloram (100 g L-1) + Triclopyr (150 g L -1) 2.0 L ha-1 + 1.5 L ha-1 of 2,4-D (3.5 L ha-1), Aminopyralid (50 g L-1) + Picloram (100 g L-1) + Triclopyr (100 g L-1) 1 L ha-1 + 1.0 L ha-1 of 2,4-D (2 L ha-1). After the harvests, the samples were identified and the following statistics were calculated — absolute frequency, relative frequency, absolute density, relative density, absolute abundance, relative abundance, and importance value index. The obtained phytosociological survey in pasture planting presented five families — Fabaceae, Malvaceae, Asteraceae, Euphorbiaceae, and Solanaceae —, and using Aminopyralid (50 g L-1) + Picloram (100 g L-1) + Triclopyr (100 g L-1), adding up to a mixture of 1.0 L ha-1, mixed with 1.0 L ha-1 of 2,4-D, was effective in the control of weeds in the pasture area.