Reactions of atomic and molecular ions with acetone, 1,1,1- trifluoroacetone, and hexafluoroacetone: An investigation of the effects of molecular structure on the dynamics and kinetics of ion-molecule reactions

A selected ion flow tube study of the reactions of a series of gas-phase atomic cations (S⁺, Xe⁺, O⁺, Kr⁺, N⁺, Ar⁺ and Ne⁺) and molecular ions (SF _n⁺ (n = 1-5), CF_n⁺ (n = 1-3), CF₂Cl⁺, H₃O⁺, NO⁺, N ₂O⁺, CO₂⁺, CO⁺, and N₂⁺) spanning a large range of recombination energies (6.3-21.6 eV), with acetone, 1,1,1-trifluoroacetone, and hexafluoroacetone has been undertaken with the objective of exploring the nature of the reaction ion chemistry as the methyl groups in acetone are substituted for CF₃. The reaction rate coefficients and product ion branching ratios for all 66 reactions, measured at 298 K, are reported. The experimental reaction rate coefficients are compared to theoretically calculated collisional values. Several distinct reaction processes were observed among the large number of reactions studied, including charge transfer (non-dissociative and dissociative), abstraction, ion-molecule associations and, in the case of the reactions involving the reagent ion H₃O⁺, proton transfer. 

Angler Perception and Population Dynamics of the Northern Snakehead (Channa argus) in the Potomac River & Tributaries

Our research sought to address the extent to which the northern snakehead (Channa argus), an invasive fish species, represents a threat to the Potomac River ecosystem. The first goal of our research was to survey the perceptions and opinions of recreational anglers on the effects of the snakehead population in the Potomac River ecosystem. To determine angler perceptions, we created and administered 113 surveys from June – September 2014 at recreational boat ramps along the Potomac River. Our surveys were designed to expand information collected during previous surveys conducted by the U.S. Fish and Wildlife Service. Our results indicated recreational anglers perceive that abundances and catch rates of target species, specifically largemouth bass, have declined since snakehead became established in the river. The second goal of our research was to determine the genetic diversity and potential of the snakehead population to expand in the Potomac River. We hypothesized that the effective genetic population size would be much less than the census size of the snakehead population in the Potomac River. We collected tissue samples (fin clippings) from 79 snakehead collected in a recreational tournament held between Fort Washington and Wilson’s Landing, MD on the Potomac River and from electrofishing sampling conducted by the Maryland Department of Natural Resources in Pomonkey Creek, a tributary of the Potomac River. DNA was extracted from the tissue samples and scored for 12 microsatellite markers, which had previously been identified for Potomac River snakehead. Microsatellite allele frequency data were recorded and analyzed in the software programs GenAlEx and NeEstimator to estimate heterozygosity and effective genetic population size. Resampling simulations indicated that the number of microsatellites and the number of fish analyzed provided sufficient precision. Simulations indicated that the effective population size estimate would expect to stabilize for samples > 70 individual snakehead. Based on a sample of 79 fish scored for 12 microsatellites, we calculated an Ne of 15.3 individuals. This is substantially smaller than both the sample size and estimated population size. We conclude that genetic diversity in the snakehead population in the Potomac River is low because the population has yet to recover from a genetic bottleneck associated with a founder effect due to their recent introduction into the system.

Variational ensemble Kalman filtering applied to data assimilation problems in computational fluid dynamics

One challenge on data assimilation (DA) methods is how the error covariance for the model state is computed. Ensemble methods have been proposed for producing error covariance estimates, as error is propagated in time using the non-linear model. Variational methods, on the other hand, use the concepts of control theory, whereby the state estimate is optimized from both the background and the measurements. Numerical optimization schemes are applied which solve the problem of memory storage and huge matrix inversion needed by classical Kalman filter methods. Variational Ensemble Kalman filter (VEnKF), as a method inspired the Variational Kalman Filter (VKF), enjoys the benefits from both ensemble methods and variational methods. It avoids filter inbreeding problems which emerge when the ensemble spread underestimates the true error covariance. In VEnKF this is tackled by resampling the ensemble every time measurements are available. One advantage of VEnKF over VKF is that it needs neither tangent linear code nor adjoint code. In this thesis, VEnKF has been applied to a two-dimensional shallow water model simulating a dam-break experiment. The model is a public code with water height measurements recorded in seven stations along the 21:2 m long 1:4 m wide flume’s mid-line. Because the data were too sparse to assimilate the 30 171 model state vector, we chose to interpolate the data both in time and in space. The results of the assimilation were compared with that of a pure simulation. We have found that the results revealed by the VEnKF were more realistic, without numerical artifacts present in the pure simulation. Creating a wrapper code for a model and DA scheme might be challenging, especially when the two were designed independently or are poorly documented. In this thesis we have presented a non-intrusive approach of coupling the model and a DA scheme. An external program is used to send and receive information between the model and DA procedure using files. The advantage of this method is that the model code changes needed are minimal, only a few lines which facilitate input and output. Apart from being simple to coupling, the approach can be employed even if the two were written in different programming languages, because the communication is not through code. The non-intrusive approach is made to accommodate parallel computing by just telling the control program to wait until all the processes have ended before the DA procedure is invoked. It is worth mentioning the overhead increase caused by the approach, as at every assimilation cycle both the model and the DA procedure have to be initialized. Nonetheless, the method can be an ideal approach for a benchmark platform in testing DA methods. The non-intrusive VEnKF has been applied to a multi-purpose hydrodynamic model COHERENS to assimilate Total Suspended Matter (TSM) in lake Säkylän Pyhäjärvi. The lake has an area of 154 km2 with an average depth of 5:4 m. Turbidity and chlorophyll-a concentrations from MERIS satellite images for 7 days between May 16 and July 6 2009 were available. The effect of the organic matter has been computationally eliminated to obtain TSM data. Because of computational demands from both COHERENS and VEnKF, we have chosen to use 1 km grid resolution. The results of the VEnKF have been compared with the measurements recorded at an automatic station located at the North-Western part of the lake. However, due to TSM data sparsity in both time and space, it could not be well matched. The use of multiple automatic stations with real time data is important to elude the time sparsity problem. With DA, this will help in better understanding the environmental hazard variables for instance. We have found that using a very high ensemble size does not necessarily improve the results, because there is a limit whereby additional ensemble members add very little to the performance. Successful implementation of the non-intrusive VEnKF and the ensemble size limit for performance leads to an emerging area of Reduced Order Modeling (ROM). To save computational resources, running full-blown model in ROM is avoided. When the ROM is applied with the non-intrusive DA approach, it might result in a cheaper algorithm that will relax computation challenges existing in the field of modelling and DA.

Microbial nitrogen dynamics in organic and mineral soil horizons along a latitudinal transect in western Siberia

Soil N availability is constrained by the breakdown of N-containing polymers such as proteins to oligopeptides and amino acids that can be taken up by plants and microorganisms. Excess N is released from microbial cells as ammonium (N mineralization), which in turn can serve as substrate for nitrification. According to stoichiometric theory, N mineralization and nitrification are expected to increase in relation to protein depolymerization with decreasing N limitation, and thus from higher to lower latitudes and from topsoils to subsoils. To test these hypotheses, we compared gross rates of protein depolymerization, N mineralization and nitrification (determined using N-15 pool dilution assays) in organic topsoil, mineral topsoil, and mineral subsoil of seven ecosystems along a latitudinal transect in western Siberia, from tundra (67 degrees N) to steppe (54 degrees N). The investigated ecosystems differed strongly in N transformation rates, with highest protein depolymerization and N mineralization rates in middle and southern taiga. All N transformation rates decreased with soil depth following the decrease in organic matter content. Related to protein depolymerization, N mineralization and nitrification were significantly higher in mineral than in organic horizons, supporting a decrease in microbial N limitation with depth. In contrast, we did not find indications for a decrease in microbial N limitation from arctic to temperate ecosystems along the transect. Our findings thus challenge the perception of ubiquitous N limitation at high latitudes, but suggest a transition from N to C limitation of microorganisms with soil depth, even in high-latitude systems such as tundra and boreal forest.

Partial molar volumes of l-serine and l-threonine in aqueous ammonium sulfate solutions at (278.15, 288.15, 298.15, and 308.15) K

In this study, the partial molar volumes of L-serine and L-threonine in aqueous solutions of ammonium sulfate at (0.0, 0.1, 0.3, 0.7, and 1.0) mol.kg(-1) are reported between 278.15 and 308.15 K. Transfer volumes and hydration numbers were obtained, which are larger in L-serine than in L-threonine. Dehydration of the amino acids is observed, rising with the temperature and salt molality. The data suggest that interactions between ions and charged/hydrophilic groups are predominant, and by applying the McMillan and Mayer formalism, it was concluded that they are mainly pair wise. The combination of the data presented in this study with solubility and molecular dynamics data suggests a stronger interaction of the ammonium cation with the zwitterionic centers of the amino acids when compared to the interactions of those centers with the sulfate anion.

Urban dynamics evaluation of Envigado city

This article presents the methodological conceptualization and the main results of a System Dynamics model, which main objective is to support the housing policies in the city of Envigado -- The used methodology developed a scenario-based model to emulate the approximate evolution of the housing demand and supply for the city, using a scenario of the Gross Domestic Product (GDP) and a housing authorization strategy as input -- Diverse results were obtained, for instance it was found that due to the soil availability, the housing supply reaches the saturation point between 2040 and 2046 -- Finally this article could be considered as an example of how academic tools such as System Dynamics can be used by decisions makers in the government

The Applicability Of Ordered Mesoporous Sba-15 And Its Hydrophobic Glutaraldehyde-bridge Derivative To Improve Ibuprofen-loading In Releasing System.

The mesoporous SBA-15 silica with uniform hexagonal pore, narrow pore size distribution and tuneable pore diameter was organofunctionalized with glutaraldehyde-bridged silylating agent. The precursor and its derivative silicas were ibuprofen-loaded for controlled delivery in simulated biological fluids. The synthesized silicas were characterized by elemental analysis, infrared spectroscopy, (13)C and (29)Si solid state NMR spectroscopy, nitrogen adsorption, X-ray diffractometry, thermogravimetry and scanning electron microscopy. Surface functionalization with amine containing bridged hydrophobic structure resulted in significantly decreased surface area from 802.4 to 63.0 m(2) g(-1) and pore diameter 8.0-6.0 nm, which ultimately increased the drug-loading capacity from 18.0% up to 28.3% and a very slow release rate of ibuprofen over the period of 72.5h. The in vitro drug release demonstrated that SBA-15 presented the fastest release from 25% to 27% and SBA-15GA gave near 10% of drug release in all fluids during 72.5 h. The Korsmeyer-Peppas model better fits the release data with the Fickian diffusion mechanism and zero order kinetics for synthesized mesoporous silicas. Both pore sizes and hydrophobicity influenced the rate of the release process, indicating that the chemically modified silica can be suggested to design formulation of slow and constant release over a defined period, to avoid repeated administration.

15-deoxy-Δ12,14-prostaglandin J2 Reduces Albumin-induced Arthritis In Temporomandibular Joint Of Rats.

The aim of this study was to evaluate the peripheral effect of 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) in albumin-induced arthritis in temporomandibular joint (TMJ) of rats. Antigen-induced arthritis (AIA) was generated in rats with methylated bovine serum albumin (mBSA) diluted in complete Freund׳s adjuvant. Pretreatment with an intra-articular injection of 15d-PGJ2 (100 ng/TMJ) before mBSA intra-articular injection (10 µg/TMJ) (challenge) in immunized rats significantly reduced the albumin-induced arthritis inflammation. The results demonstrated that 15d-PGJ2 was able to inhibit plasma extravasation, leukocyte migration and the release of inflammatory cytokines IL-6, IL-12, IL-18 and the chemokine CINC-1 in the TMJ tissues. In addition, 15d-PGJ2 was able to increase the expression of the anti-adhesive molecule CD55 and the anti-inflammatory cytokine IL-10. Taken together, it is possible to suggest that 15d-PGJ2 inhibit leukocyte infiltration and subsequently inflammatory process, through a shift in the balance of the pro- and anti-adhesive properties. Thus, 15d-PGJ2 might be used as a potential anti-inflammatory drug to treat arthritis-induced inflammation of the temporomandibular joint.

Utilization Of (15)no3 (-) By Nodulated Soybean Plants Under Conditions Of Root Hypoxia.

Waterlogging of soils is common in nature. The low availability of oxygen under these conditions leads to hypoxia of the root system impairing the development and productivity of the plant. The presence of nitrate under flooding conditions is regarded as being beneficial towards tolerance to this stress. However, it is not known how nodulated soybean plants, cultivated in the absence of nitrate and therefore not metabolically adapted to this compound, would respond to nitrate under root hypoxia in comparison with non-nodulated plants grown on nitrate. A study was conducted with (15)N labelled nitrate supplied on waterlogging for a period of 48 h using both nodulated and non-nodulated plants of different physiological ages. Enrichment of N was found in roots and leaves with incorporation of the isotope in amino acids, although to a much smaller degree under hypoxia than normoxia. This demonstrates that nitrate is taken up under hypoxic conditions and assimilated into amino acids, although to a much lesser extent than for normoxia. The similar response obtained with nodulated and non-nodulated plants indicates the rapid metabolic adaptation of nodulated plants to the presence of nitrate under hypoxia. Enrichment of N in nodules was very much weaker with a distinct enrichment pattern of amino acids (especially asparagine) suggesting that labelling arose from a tissue source external to the nodule rather than through assimilation in the nodule itself.

Mechanical Properties And Fracture Dynamics Of Silicene Membranes.

As graphene has become one of the most important materials, there is renewed interest in other similar structures. One example is silicene, the silicon analogue of graphene. It shares some of the remarkable graphene properties, such as the Dirac cone, but presents some distinct ones, such as a pronounced structural buckling. We have investigated, through density functional based tight-binding (DFTB), as well as reactive molecular dynamics (using ReaxFF), the mechanical properties of suspended single-layer silicene. We calculated the elastic constants, analyzed the fracture patterns and edge reconstructions. We also addressed the stress distributions, unbuckling mechanisms and the fracture dependence on the temperature. We analysed the differences due to distinct edge morphologies, namely zigzag and armchair.

Site Specific Spin Dynamics In Bafe2as2: Tuning The Ground State By Orbital Differentiation.

The role of orbital differentiation on the emergence of superconductivity in the Fe-based superconductors remains an open question to the scientific community. In this investigation, we employ a suitable microscopic spin probe technique, namely Electron Spin Resonance (ESR), to investigate this issue on selected chemically substituted BaFe2As2 single crystals. As the spin-density wave (SDW) phase is suppressed, we observe a clear increase of the Fe 3d bands anisotropy along with their localization at the FeAs plane. Such an increase of the planar orbital content is interestingly independent of the chemical substitution responsible for suppressing the SDW phase. As a consequence, the magnetic fluctuations in combination with this particular symmetry of the Fe 3d bands are propitious ingredients for the emergence of superconductivity in this class of materials.

[between The Country And The Laboratory: The Dynamics Of The Production Of Knowledge At The Menopause Outpatients Clinic At Caism, Unicamp.]

This study investigates the practices involved in the production of knowledge about menopause at Caism, Unicamp, a reference center for public policies for women's health. Gynecological appointments and psychological support meetings were observed, and women and doctors were interviewed in order to identify what discourse circulates there and how different actors are brought in to ensure that the knowledge produced attains credibility and travels beyond the boundaries of the teaching hospital to become universal. The analysis is based on localized studies aligned with social studies of science and technology.

[between The Country And The Laboratory: The Dynamics Of The Production Of Knowledge At The Menopause Outpatients Clinic At Caism, Unicamp].

This study investigates the practices involved in the production of knowledge about menopause at Caism, Unicamp, a reference center for public policies for women's health. Gynecological appointments and psychological support meetings were observed, and women and doctors were interviewed in order to identify what discourse circulates there and how different actors are brought in to ensure that the knowledge produced attains credibility and travels beyond the boundaries of the teaching hospital to become universal. The analysis is based on localized studies aligned with social studies of science and technology.

In vitro Microfluidic Model For The Study Of Vaso-occlusive Processes.

Vaso-occlusion, responsible for much of the morbidity of sickle-cell disease, is a complex multicellular process, apparently triggered by leukocyte adhesion to the vessel wall. The microcirculation represents a major site of leukocyte-endothelial interactions and vaso-occlusive processes. We have developed a biochip with subdividing interconnecting microchannels that decrease in size (40 μm to 10 μm in width), for use in conjunction with a precise microfluidic device, to mimic cell flow and adhesion through channels of sizes that approach those of the microcirculation. The biochips were utilized to observe the dynamics of the passage of neutrophils and red blood cells, isolated from healthy and sickle-cell anemia (SCA) individuals, through laminin or endothelial adhesion molecule-coated microchannels at physiologically relevant rates of flow and shear stress. Obstruction of E-selectin/intercellular adhesion molecule 1-coated biochip microchannels by SCA neutrophils was significantly greater than that observed for healthy neutrophils, particularly in the microchannels of 40-15 μm in width. Whereas SCA red blood cells alone did not significantly adhere to, or obstruct, microchannels, mixed suspensions of SCA neutrophils and red blood cells significantly adhered to and obstructed laminin-coated channels. Results from this in vitro microfluidic model support a primary role for leukocytes in the initiation of SCA occlusive processes in the microcirculation. This assay represents an easy-to-use and reproducible in vitro technique for understanding molecular mechanisms and cellular interactions occurring in subdividing microchannels of widths approaching those observed in the microvasculature. The assay could hold potential for testing drugs developed to inhibit occlusive mechanisms such as those observed in SCA and thrombotic diseases.

Gases e ruídos em edificações para suínos: aplicação das normas NR-15, CIGR e ACGIH

Swine production represents an important segment of Brazilian economy, and the possibility of increasing production is eminent mainly if considered the low pork consumption when compared to other meat and the consumption of other countries. The increasing need in the international market demands show that in a near future the commercial barriers will be based on welfare, in the protection of the environment as well as in the worker's legislation. Little knowledge is available in the subject of worker's standards in the environmental agents in rural activities as well as the air quality under Brazilian conditions. The objectives of this research were to apply the main used standards related to noise and gases and to estimate occupational risk using measurements of noise level, hydrogen sulfide, methane and oxygen in swine housing, in piglet's nursery and finishing. The results showed that the continuous noise level were below the one found in the standards, however there were observed differences (P < 0.05) in relation to the noise level measured in piglet's nursing cages and in semi-slatted floor. The respective concentrations of hydrogen sulfide and methane were less than 1 ppm and less than 0,1% by volume, which was lower than the recommended limits in NR-15, CIGR and ACGIH. The oxygen level was 21% in average.