Experimental and Analytical Study of Two-Phase Flow in Microgravity

Design of the two-phase flow systems which are anticipated to be utilized in future spacecraft thermal management systems requires a knowledge of two-phase flow and heat transfer parameters in reduced gravities. A program has been initiated by NASA to design a two-phase test loop and to perform a series of experiments to study the effect of gravity on the Critical Heat Flux (CHF) and onset of instability. The test loop is also instrumented to generate data for two-phase pressure drop. In addition to low gravity airplane trajectory testing, the experimental program consisted of a set of laboratory tests which were intended to generate data under the bounding conditions (+1 g and -1 g) in order to plan the test matrix. One set of airplane trajectory tests has been performed and several modifications to the test set-up have been identified. Preliminary test results have been used to demonstrate the applicability of the earth gravity models for prediction of the two-phase friction pressure drop

Representative elementary volumes for evaluating effective seismic properties of heterogeneous poroelastic media

Understanding and quantifying seismic energy dissipation in fluid-saturated porous rocks is of considerable interest because it offers the perspective of extracting information with regard to the elastic and hydraulic rock properties. An important, if not dominant, attenuation mechanism prevailing in the seismic frequency band is wave-induced fluid pressure diffusion in response to the contrasts in elastic stiffness in the mesoscopic-scale range. An effective way to estimate seismic velocity dispersion and attenuation related to this phenomenon is through the application of numerical upscaling procedures to synthetic rock samples of interest. However, the estimated seismic properties are meaningful only if the underlying sample volume is at least of the size of a representative elementary volume (REV). In the given context, the definition of an REV and the corresponding implications for the estimation of the effective seismic properties remain largely unexplored. To alleviate this problem, we have studied the characteristics of REVs for a set of idealized rock samples sharing high levels of velocity dispersion and attenuation. For periodically heterogeneous poroelastic media, the REV size was driven by boundary condition effects. Our results determined that boundary condition effects were absent for layered media and negligible in the presence of patchy saturation. Conversely, strong boundary condition effects arose in the presence of a periodic distribution of finite-length fractures, thus leading to large REV sizes. The results thus point to the importance of carefully determining the REV sizes of heterogeneous porous rocks for computing effective seismic properties, especially in the presence of strong dry frame stiffness contrasts. </jats:p

An analytical study of seismoelectric signals produced by 1-D mesoscopic heterogeneities

The presence of mesoscopic heterogeneities in fluid-saturated porous rocks can produce measurable seismoelectric signals due to wave-induced fluid flow between regions of differing compressibility. The dependence of these signals on the petrophysical and structural characteristics of the probed rock mass remains largely unexplored. In this work, we derive an analytical solution to describe the seismoelectric response of a rock sample, containing a horizontal layer at its centre, that is subjected to an oscillatory compressibility test. We then adapt this general solution to compute the seismoelectric signature of a particular case related to a sample that is permeated by a horizontal fracture located at its centre. Analyses of the general and particular solutions are performed to study the impact of different petrophysical and structural parameters on the seismoelectric response. We find that the amplitude of the seismoelectric signal is directly proportional to the applied stress, to the Skempton coefficient contrast between the host rock and the layer, and to a weighted average of the effective excess charge of the two materials. Our results also demonstrate that the frequency at which the maximum electrical potential amplitude prevails does not depend on the applied stress or the Skempton coefficient contrast. In presence of strong permeability variations, this frequency is rather controlled by the permeability and thickness of the less permeable material. The results of this study thus indicate that seismoelectric measurements can potentially be used to estimate key mechanical and hydraulic rock properties of mesoscopic heterogeneities, such as compressibility, permeability and fracture complianc

An analytical study of seismoelectric signals produced by 1-D mesoscopic heterogeneities

The presence of mesoscopic heterogeneities in fluid-saturated porous rocks can produce measurable seismoelectric signals due to wave-induced fluid flow between regions of differing compressibility. The dependence of these signals on the petrophysical and structural characteristics of the probed rock mass remains largely unexplored. In this work, we derive an analytical solution to describe the seismoelectric response of a rock sample, containing a horizontal layer at its center, that is subjected to an oscillatory compressibility test. We then adapt this general solution to compute the seismoelectric signature of a particular case related to a sample that is permeated by a horizontal fracture located at its center. Analyses of the general and particular solutions are performed to study the impact of different petrophysical and structural parameters on the seismoelectric response. We find that the amplitude of the seismoelectric signal is directly proportional to the applied stress, to the Skempton coefficient contrast between the host rock and the layer, and to a weighted average of the effective excess charge of the two materials. Our results also demonstrate that the frequency at which the maximum electrical potential amplitude prevails does not depend on the applied stress or the Skempton coefficient contrast. In presence of strong permeability variations, this frequency is rather controlled by the permeability and thickness of the less permeable material. The results of this study thus indicate that seismoelectric measurements can potentially be used to estimate key mechanical and hydraulic rock properties of mesoscopic heterogeneities, such as compressibility, permeability, and fracture compliance.Comment: 14 pages, 8 figure

Isolation and selection of rhizospheric bacteria with biofertilizing potential for corn cultivation

&nbsp;Objective: isolate and determine at the greenhouse level the biofertilizing potential of rhizospheric bacteria associated with corn in the state of Campeche Design/methodology/approach: Rhizospheric soils were collected in zones with different management conditions. Bacterial strain were isolated from these samples and their biofertilizing potential was determined by in vitro and in vivo The data obtained in both tests were analyzed by analysis of variance (ANOVA) and a means comparison test (LSD, p? 0.01). Results: In total 16 rhizospheric bacteria were isolated, a greater number of strains in non-mechanized soils (n=10) compared to mechanized soils (n=6). In in vitro tests, the most representative activity corresponded to nitrogen fixation (81%) attributed to a higher percentage of bacteria, while the activity with a lower number of bacteria corresponded to the production IAA (25%). In in vivo tests in corn plants, theYM1 strain presented the highest fresh and dry root weight (20.00 and 2.00 g plant-1), the YM4 strain the highest height (63.33 cm), and YM5 the highest values in diameter stem (7.13 mm), root lenght (36.78 cm) and fresh weigh of the stem (12.03 g plant-1) Limitations on study/implications: Strain evaluation is limited to controlled greenhouse conditions. Findings/conclusions: The YM1, YM4 and YM5 strains show potential to be evaluated in the future as biofertilizers in the cultivation of corn in the fieldObjective: To isolate and determine in a greenhouse environment the biofertilizingpotential of rhizospheric bacteria associated to corn (Zea mays L.) at Campeche,Mexico.Design / methodology / approach: Rhizospheric soils were collected from twocorn production zones with different management conditions. Bacterial strains wereisolated from these samples and their biofertilizing potential determined by in vitro2 and in vivo tests. The obtained data from both tests were assessed using ananalysis of variance (ANOVA) and a means comparison test (LSD, p ? 0.01).Results: In total, 16 rhizospheric bacteria were isolated, a higher number in non-mechanized soils (n = 10) compared to mechanized ones (n = 6). In the in vitrotests, the most representative activity corresponds to nitrogen fixation (81%)attributed to a higher bacteria percentage, while the activity with lower bacterianumbers corresponds to IAA production (25%). At the in vivo tests in corn plants,the YM1 strain presented the highest fresh and dry root biomass (20 and 2 g plant -1 , respectively). The YM4 strain promoted greater plant height (63.33 cm), and YM5registered the highest values in stem diameter (7.13 mm), root length (36.78 cm)and fresh shoot weight (12.03 g plant -1 ).Limitations / Implications: Strain evaluations were limited to controlledgreenhouse conditions.Conclusion: The YM1, YM4 and YM5 strains show potential for further evaluationas biofertilizers for corn cultivation under field conditions

Counteranion-Dependent Reaction Pathways in the Protonation of Cationic Ruthenium−Vinylidene Complexes

The tetraphenylborate salts of the cationic vinylidene complexes [Cp*Ru=C=CHR(iPr2PNHPy)]+ (R = p-C6H4CF3 (1a-BPh4), Ph (1b-BPh4), p-C6H4CH3 (1c- BPh4), p-C6H4Br (1d-BPh4), tBu (1e-BPh4), H (1f-BPh4)) have been protonated using an excess of HBF4·OEt2 in CD2Cl2, furnishing the dicationic carbyne complexes [Cp*Ru≡CCH2R(iPr2PNHPy)]2+ (R = p-C6H4CF3 (2a), Ph (2b), p-C6H4CH3 (2c), p-C6H4Br (2d), tBu (2e), H (2f)), which were characterized in solution at low temperature by NMR spectroscopy. The corresponding reaction of the chloride salts 1a-Cl, 1b-Cl, 1c-Cl, and 1d-Cl followed a different pathway, instead affording the novel alkene complexes [Cp*RuCl(κ1(N),η2(C,C)-C5H4N-NHPiPr2CH=CHR)][BF4] (3a−d). In these species, the entering proton is located at the α- carbon atom of the former vinylidene ligand, which also forms a P−C bond with the phosphorus atom of the iPr2PNHPy ligand. To shed light on the reaction mechanism, DFT calculations have been performed by considering several protonation sites. The computational results suggest metal protonation followed by insertion. The coordination of chloride to ruthenium leads to alkenyl species which can undergo a P−C coupling to yield the corresponding alkene complexes. The noncoordinating nature of [BPh4]− does not allow the stabilization of the unsaturated species coming from the insertion step, thus preventing this alternative pathway

Suppression of Phospholipase Dγs Confers Increased Aluminum Resistance in Arabidopsis thaliana

Aluminum (Al) toxicity is the major stress in acidic soil that comprises about 50% of the world's arable land. The complex molecular mechanisms of Al toxicity have yet to be fully determined. As a barrier to Al entrance, plant cell membranes play essential roles in plant interaction with Al, and lipid composition and membrane integrity change significantly under Al stress. Here, we show that phospholipase Dγs (PLDγs) are induced by Al stress and contribute to Al-induced membrane lipid alterations. RNAi suppression of PLDγ resulted in a decrease in both PLDγ1 and PLDγ2 expression and an increase in Al resistance. Genetic disruption of PLDγ1 also led to an increased tolerance to Al while knockout of PLDγ2 did not. Both RNAi-suppressed and pldγ1-1 mutants displayed better root growth than wild-type under Al stress conditions, and PLDγ1-deficient plants had less accumulation of callose, less oxidative damage, and less lipid peroxidation compared to wild-type plants. Most phospholipids and glycolipids were altered in response to Al treatment of wild-type plants, whereas fewer changes in lipids occurred in response to Al stress in PLDγ mutant lines. Our results suggest that PLDγs play a role in membrane lipid modulation under Al stress and that high activities of PLDγs negatively modulate plant tolerance to Al

Portuguese recommendations for the use of biological and targeted synthetic diseasemodifying antirheumatic drugs in patients with rheumatoid arthritis – 2020 update

Objective: To update the recommendations for the treatment of rheumatoid arthritis (RA) with biological and targeted synthetic disease-modifying antirheumatic drugs (bDMARDs and tsDMARDs), endorsed by the Portuguese Society of Rheumatology (SPR). Methods: These treatment recommendations were formulated by Portuguese rheumatologists taking into account previous recommendations, new literature evidence and consensus opinion. At a national meeting, in a virtual format, three of the ten previous recommendations were re-addressed and discussed after a more focused literature review. A first draft of the updated recommendations was elaborated by a team of SPR rheumatologists from the SPR rheumatoid arthritis study group, GEAR. The resulting document circulated among all SPR rheumatologists for discussion and input. The level of agreement with each of all the recommendations was anonymously voted online by all SPR rheumatologists. Results: These recommendations cover general aspects such as shared decision, treatment objectives, systematic assessment of disease activity and burden and its registry in Reuma.pt. Consensus was also achieved regarding specific aspects such as initiation of bDMARDs and tsDMARDs, assessment of treatment response, switching and definition of persistent remission. Conclusion: These recommendations may be used for guidance of treatment with bDMARDs and tsDMARDs in patients with RA. As more evidence becomes available and more therapies are licensed, these recommendations will be updated.info:eu-repo/semantics/publishedVersio