Extent Of Retention Research Articles

The impact of dissolved organic nitrogen (DON) retention in the vadose zone on nitrogen leaching losses

Leaching of dissolved organic nitrogen (DON) is a significant pathway for nitrogen (N) loss in agricultural ecosystems. The excessive application of N for enhanceing agricultural productivity often results in the leaching of N into groundwater. Yet not well understood, the extent of retention in the vadose zone has critical implications for risk management and remediation strategies. This study aims to advance simulation techniques for modelling the transport process of reactive DON within a heterogeneous vadose zone. Through a combination of laboratory experiments and numerical simulations, the study firstly examines the extent of DON retention in the vadose zone and quantitatively analyse groundwater contamination risk from this kind of accumulation. Our findings indicate that heavy N fertilizer application and high-intensity rainfall events led to elevated contents of DON in the vadose zone and increased DON leaching fluxes into groundwater. Besides, intensifier rainfall reduced the N storage more quickly in scenarios devoid of DON application with higher mineralization rate, while DON slowly mineralized to other forms, largely accumulated in the top layer and migrated deeper with intensifier rainfall after input of urea. In our scenarios, DON accounted for a substantial portion (33–68%) of the total dissolved nitrogen (TDN) leaching fluxes, with exogenous DON content contributing significantly (25–85%) to the overall DON leaching into the aquifer. These results underscore the need for effective strategies to mitigate groundwater contamination risks associated with agricultural N use.

Sputtering and reflection processes from amorphous lithium surfaces by low-energy impacts of H and D atoms and D2 molecules

This work presents a computational study of the retention, reflection, and sputtering processes at amorphous and crystalline lithium surfaces by the impact of low energy (5-100 eV) hydrogen and deuterium atoms and D2 molecules for a range of incident angles of 0° (normal to the surface) to 85°. Classical molecular dynamics simulations were performed with the reactive bond-order force field (ReaxFF) potentials. Effects of the temperature of the surface slab were also considered. The extent of retention, and the energy and angular distributions of reflected and sputtered atoms were determined. Comparison of the results of these simulations with available experimental data on the sputtering rate for Li atoms is in good agreement for incident angles of 0°, and the simulation results predict significant increase in the sputtering probabilities for incident angles larger than 30°.

Retention of Iodide and Chloride by Formation of a Green Rust Solid Solution GR-Cl1-xIx: A Multiscale Approach.

The uptake of iodide and chloride during the synthesis of green rust (GR), the Fe endmember of the layered double hydroxide (LDH) group, was investigated. GR compounds were prepared by aerial oxidation of Fe(OH)2 in suspension, considering various I/Cl ratios at constant ionic strength. Only GR compounds formed in all experiments, and the associated I/Cl ratio increased with that of the starting suspension. No preferential uptake of any halide could be detected, and all compounds had comparable morphology. Furthermore, the height of the interlayer gallery increased with the I/Cl ratio from ∼7.7 Å for the chloride endmember to ∼8.3 Å for the iodide endmember, and the observed linear increase was attributed to increasing interlayer iodide content. In all compounds, Fe K-edge X-ray absorption spectroscopy evidenced the presence of sixfold coordinated iron with a Fe2+/Fe3+ ratio of 3, homogeneously distributed within flattened octahedral sites, with six Fe as next-nearest neighbors. The Fe short-range environment was not affected by the interlayer composition, and no halide from the interlayer could be detected. Furthermore, iodide and chloride anions are located in a water-like environment, being loosely bound by weak electrostatic interactions to the octahedral sheet likely above ferric iron. Results consistently hint at the formation of a solid solution between chloride and iodide GR endmembers, certainly facilitated by the crystallization of both compounds in the same space group. This study provides further insights into the ability of LDH to simultaneously accommodate several anionic species of various sizes. The formation of such LDH compounds in a deep geological repository for nuclear waste thus represents a possible retention barrier to the migration to the far field of anionic species like 36Cl- and 129I- mobilized from the waste matrix. The extent of retention in disposal sites will depend, among others, on the availability of GR and on the concentration of competing anions.

A Mathematical Model for the Release, Transport, and Retention of Per- and Polyfluoroalkyl Substances (PFAS) in the Vadose Zone.

Per- and Polyfluoroalkyl Substances (PFAS) are emerging contaminants of critical concern. As surfactants, PFAS tend to accumulate at air-water interfaces and may stay in the vadose zone for long times before contaminating groundwater. Yet not well understood, the extent of retention in the vadose zone has critical implications for risk management and remediation strategies. We present the first mathematical model that accounts for surfactant-induced flow and solid-phase and air-water interfacial adsorption. We apply the model to simulate PFOS (a PFAS compound of primary concern) transport in the vadose zone at a model fire-training area site impacted by Aqueous Film-Forming Foam (AFFF). Air-water interfacial adsorption is shown to have a significant impact-amplified by the low water content due to gravity drainage-total retardation factors range from 233 to 1355 for the sand and 146 to 792 for the soil used in the study. The simulations illustrate it can take several decades or longer for PFOS to reach groundwater. Counterintuitively, the lower water content in the sand-due to stronger drainage and weaker capillary retention-leads to retardation factors greater than for the soil. Also, most PFOS is adsorbed at air-water interfaces with only 1-2% in the aqueous phase. The implications include 1) fine-texture materials could have lower retardation factors than sand due to higher retained water content, 2) soil PFAS concentrations are likely to be orders of magnitude higher than those in groundwater at source zones. Both implications are consistent with recent field observations at hundreds of AFFF-impacted sites.

Smart options for simultaneous functionalization and pigment coloration of cellulosic/wool blends

The present innovative research work deals with the individual use of chitosan (2.5g/kg), Aloe vera (10g/kg), triclosan (10g/kg), TiO2-nanoparticles (TiO2-NP's, 10g/kg), silicon micro-emulsion (20g/kg) or a water/oil-repellent agent (40g/kg) for modifying the pigment print paste to produce functionalized cotton/wool and viscose/wool pigment prints in one step process. The imparted functional properties such as antibacterial, antibacterial/UV-protection, soft-handle or water/oil-repellency together with the change in the printing properties were evaluated. Some of the obtained pigment prints were characterized by scanning electron microscope (SEM), and energy dispersive X-rays (EDX) to confirm deposition of certain functional additives on printed fabrics. The wide-range of imparted functional properties together with the depth of the obtained pigment prints were maintained over 80% even after 15 consecutive laundering cycles. The extent of retention in functional and pigment printing properties is influenced by the type of functional additive as well as the kind of substrate.

Phosphodiesterase 4 inhibition attenuates plasma volume loss and transvascular exchange in volume expanded mice

Phosphodiesterase 4 inhibition attenuates plasma volume loss and transvascular exchange in volume expanded mice

Comprehensive two-dimensional gas chromatography applied to illicit drug analysis

Multidimensional gas chromatography (MDGC), and especially its latest incarnation--comprehensive two-dimensional gas chromatography (GC × GC)--have proved advantageous over and above classic one-dimensional gas chromatography (1D GC) in many areas of analysis by offering improved peak capacity, often enhanced sensitivity and, especially in the case of GC × GC, the unique feature of 'structured' chromatograms. This article reviews recent advances in MDGC and GC × GC in drug analysis with special focus on ecstasy, heroin and cocaine profiling. Although 1D GC is still the method of choice for drug profiling in most laboratories because of its simplicity and instrument availability, GC × GC is a tempting proposition for this purpose because of its ability to generate a higher net information content. Effluent refocusing due to the modulation (compression) process, combined with the separation on two 'orthogonal' columns, results in more components being well resolved and therefore being analytically and statistically useful to the profile. The spread of the components in the two-dimensional plots is strongly dependent on the extent of retention 'orthogonality' (i.e. the extent to which the two phases possess different or independent retention mechanisms towards sample constituents) between the two columns. The benefits of 'information-driven' drug profiling, where more points of reference are usually required for sample differentiation, are discussed. In addition, several limitations in application of MDGC in drug profiling, including data acquisition rate, column temperature limit, column phase orthogonality and chiral separation, are considered and discussed. Although the review focuses on the articles published in the last decade, a brief chronological preview of the profiling methods used throughout the last three decades is given.

Effect of processing on the retention of carotenoids in yellow-fleshed cassava (Manihot esculenta Crantz) roots

Summary The retention of carotenoids was studied in roots from yellow-fleshed, high carotene cassava clones in four different processing methods. The results indicated that the extent of retention varied with the method of processing. The highest retention was observed in oven drying (total carotenoids 54.70–84.01% and β-carotene 63.90–94.53%) followed by boiling (total carotenoids 47.87–83.79% and β-carotene 51.31–81.04%) and frying (total carotenoids 48.76–79.77% and β-carotene 44.11–83.87%). The lowest retention of total carotenoids (32.86–56.40%) and β-carotene (21.47–56.68%) was recorded in the sun drying method. The variation in the total carotenoids and β-carotene content depends on variety, processing method and initial carotene content of the fresh root.

Aspects of Dynamic Recrystallization in Cobalt at High Temperatures

Deformation behavior of cobalt in the fcc phase was studied over a wide range of strain rates (0.001 to 1 s–1) and temperatures (600 °C to 950 °C). At the lower temperatures and higher strain rates, a single peak in flow stress followed by softening to steady state was observed, whereas at higher temperatures and lower strain rates, an oscillatory flow stress behavior finally converging to a steady state was observed. Both these represent typical flow stress responses during dynamic recrystallization (DRX). The critical condition for the initiation of DRX was determined by the inflection point in the work-hardening vs stress plot. This critical condition in terms of the work done was found to increase with temperature-compensated strain rate. Electron backscattered diffraction (EBSD) revealed that, on quenching after deformation, a certain fraction of the fcc phase was always retained, the extent of retention being higher for smaller grain sizes. Misorientation measurements across boundaries revealed a significant amount of twins in the retained fcc phase. The grain average misorientation (GAM), signifying the misorientation within grains, was found to be inversely related to the twin boundary fractions in the fcc phase.

Hydrophobicity and octanol-water partitioning of trace metals in natural waters.

The hydrophobicities of dissolved Al, Cu, Mn, and Pb have been determined in various contaminated natural water samples by 1-octanol extraction and C18 column retention. Octanol extraction varied among the metals studied and between the environments sampled but, in general, was greatest for Pb, whose conditional octanol-water partition coefficient, Dow, exceeded unit value in some samples. In most cases, metal partition into octanol either increased with increasing pH or exhibited a maximum under near-neutral conditions. Although the order and pH-dependence of metal retention by the C18 columns was consistent with these observations, the extent of retention was generally greater than the extent of metal extraction by octanol, possibly because of interferences effected by the C18 column matrix. Speciation calculations and results of controlled experiments employing metals in the presence of model ligands suggest that metals may become hydrophobic either by neutralizing relatively hydrophilic ligands or by combining with ligands that are intrinsically hydrophobic themselves. Given that octanol solubility affords an upper estimate of lipophilicity, the results of this investigation may have important implications regarding our understanding of metal bioavailability and toxicity in natural waters.

Two different biological configurations for long-term memory

Long-term memory (LTM) in Hermissenda can be distinguished from consolidated long-term memory (CLTM) by determining how long recall is retained. LTM is retained for approximately 1 day, while CLTM is retained for at least 3 days. During the transition from LTM to CLTM, the extent of retention appears to depend partially on how much consolidation has been completed. Several models are discussed that may be related to the two different manifestations of recall.

Removal of the Natural Hormone Estrone from Aqueous Solutions Using Nanofiltration and Reverse Osmosis

The ability of a variety of nanofiltration and reverse osmosis membranes to retain the natural hormone estrone are examined here as a function of solution conditions. While size exclusion dominates retention with the tighter membranes, both size exclusion and adsorptive effects appear to be instrumental in maintaining high retention on nanofiltration membranes that otherwise exhibit relatively low ion retentions. These adsorptive effects may be driven by hydrogen bonding between estrone and the membrane. Electrostatic attraction appears to aid retention with an apparent slight decrease in retention at high NaCl concentrations. Deprotonation of estrone leads to a significant decrease in retention, most likely as a result of the effect of strong electrostatic repulsive forces decreasing the proximity of the negatively charged estrone to the negatively charged membrane surface and thus lowering the potential for adsorptive retention. This deprotonation effect is absent for tight RO membranes. The results reported here indicate that while open nanofiltration membranes may be effective in retaining estrone under some conditions, the extent of retention may be very susceptible to maintenance of adsorptive capacity at the membrane surface and depend on solution chemistry.

A rigid poly(amidehydrazide): Morphology and mechanical behavior

A wholly aromatic all-para oriented poly(amidehydrazide) has been prepared from N,N'-bis(4-aminobenzoyl)hydrazine and terephthaloyl dichloride by solution polycondensation. Films of the polymer were prepared by two processes, viz. a wet and a dry process, by using its solution in N,N-dimethylacet-amide/LiCl. Optical anisotropy, surface morphology and tensile properties of the films were studied. Polarizing optical microscopic study reveals that the films prepared by the dry process have more pronounced birefringent characteristics and greater nematic order than the films prepared by the wet process. The birefringent characteristics in the films become more and more prominent with increase in polymer inherent viscosity. Scanning electron microscopic study reveals that when the LiCI content in the polymer solution used for the film casting is low (1 wt.-%), the corresponding films, prepared either by the wet or by the dry process, have smooth surfaces. But when the LiCI content is high (>I wt.-%), only the wet process produces films with smooth surface, whereas there are microvoids on the surface of the films prepared by the dry process. Regarding the tensile study, in general, the films prepared by the dry process have higher strength and modulus, but lower elongation than the films prepared by the wet process due to a greater extent of retention of orientation in the films prepared by the dry process. The strength and modulus of the films are found to increase with increase in the polymer inherent viscosity.

Evaluation of abnormal regional ventilation in patients with lung cancer using three-dimensional display of dynamic 133Xe SPET.

Preliminary studies were carried out of regional ventilation in lung cancer using three-dimensional (3D) display of dynamic pulmonary 133Xe single photon emission tomography (SPET). Transaxial equilibrium and washout images were obtained from SPET data acquired with an acquisition time of 30 s using a triple-detector SPET system in 39 patients with lung cancer. After reconstructing colour-illuminated, surface-rendered 3D images of equilibrium and 3-min washout (WO3), a single 3D fusion display was created from these two different time-course image sets, in which the 3D WO3 image indicating 133Xe retention was visible through the 3D equilibrium image delineating lung contours. The extent of retention was assessed using the 133Xe retention index, defined as the ratio of summed pixels of the segmented WO3 data to those of the segmented equilibrium data. 133Xe SPET was highly sensitive and specific for the presence of regional ventilation abnormalities associated with endobronchial tumour or bronchial compression due to enlarged lymph nodes. These abnormalities were demonstrated irrespective of the presence or absence of secondary changes distal to the tumour on the chest computed tomography scan. The geometrically realistic 3D fusion display enhanced anatomic localization of the regional ventilation abnormalities compared to the information from multislice tomograms, and the 133Xe retention index correlated well with %FEV1 (r = 0.828). This topographic 3D display for 133Xe SPET allows better perception of anatomic localization and extent of 133Xe retention. It will be useful for assessing regional ventilatory function in patients with lung cancer.

Injecting Fats into Breast Meat of Turkey Carcasses Differing in Finish and Retention After Cooking

ABSTRACTRetention of butter and coconut oil injected into the major breast muscles of uncooked turkey was examined. Fats were injected to 3% of thawed weight using carcasses differing in skin depots covering the breast of each sex. Cooking time was not influenced by fat injection nor was the yield of breast meat. Injecting fats led to a reduction in muscle moisture while petroleum ether extract increased. Fatty acid analysis of the extract indicated that the lipid increases were representative of the fat injected, and the extent of retention was equivalent with each fat source. Skin depots over the breast and sex of the turkey had little effect on muscle lipid and fat retention.

A case study of learning styles in biology

Summaries English The process of acquisition, and the nature and extent of retention, of a hierarchy of intellectual skills in genetics were examined for each of three adults by case study. Task materials, based on a skill hierarchy and interview protocol, were designed to promote learning with understanding. Various theoretical models and schemes were devised to identify and monitor learning processes and changes in cognitive structure of the learner. Additional information was obtained on the stability and generalizability of learning processes, and the nature and extent of retention and accessibility of learned material. Evidence was obtained for qualitative differences in learning process and outcome. Results indicate evidence for two different learning styles which involve different specific learning strategies and which differ in the extent of incorporation of new material into the learner's cognitive structure, and on the subsequent retrieval of this material. One learning style is considered parti...

Retentive solvolysis. Part XI. Retentive phenolyses of optically active secondary and tertiary systems without a group imposing configurational restriction

The rate, product distribution, and stereochemical course for phenolyses of 17 compounds, including three p-substituted 1-phenylethyl systems, eight m- or p-substituted 2,2-dimethyl-1-phenylpropyl systems, 1-phenylpropyl, 2-methyl-1-phenylpropyl, p-chlorodiphenylmethyl, and 1-methyl-1-phenylpropyl p-nitrobenzoate, and 1-ethyl-1,5-dimethylhexyl chloride and trifluoroacetate have been investigated. The titrimetric rate constants for p-substituted 1-phenylethyl p-nitrobenzoates and for m- or p-substituted 2,2-dimethyl-1-phenylpropyl p-nitrobenzoates follow the Yukawa–Tsuno correlation in pure phenol as solvent. All phenyl ethers, major products of phenolyses, show net retention of configuration: in particular, the extent of retention was 97.4% for 2,2-dimethyl-1-(p-nitrophenyl)propyl phenyl ether and 90.0% for 2,2-dimethyl-1-phenylpropyl phenyl ether in the presence of triethylamine. C-Alkylated products are formed to a small extent and show net inversion in ten phenolyses examined; among these, o- and p-(2,2-dimethyl-1-phenylpropyl) phenol which are produced from the p-nitrobenzoate show almost completely inverted configuration. Variations the polarimetric and titrimetric rates, in the product yield, and in the extent of retention have been examines for various concentrations of added base in the phenolyses of eight selected substrates. On the basis of these results, the mechanism and stereochemical course of the phenolyses are discussed by the use of a generalized scheme, previously proposed for the phenolyses of 1-phenylethyl systems. The maximum rotations and the absolute configurations of the compounds have been determined by chemical or n.m.r. shift reagent methods.

Retentive solvolysis. Part X. Retentive solvolysis of optically active para-substituted 1-phenylethyl p-nitrobenzoates in phenolic solvents: rate, steric course, product distribution, and mechanism

The title compounds (Ia)–(IIIa) were subjected to solvolysis in the presence of sodium phenoxide in pure phenol or in phenol-benzene (1 : 1 w/w) as solvent. Both polarimetric and titrimetric rate constants (Kp and Kt) decrease in the order (Ia) > (IIa) > (IIIa); Kp values for (Ia) and (IIa) exceed those for Kt over the whole range of concentration of added sodium phenoxide, whereas Kp and Kt for (IIIa) coincide with each other. The major products, the phenyl ethers (Ib)–(IIIb), show net retention of configuration; the extent of retention was 16.6% for (Ib) in phenol-benzene at 25°, 34.5% for (IIb), and 90.0% for (IIIb) in phenol at 125°, respectively. The C-alkylated products, o- and p-1-phenylethylphenols, are formed to a small extent only and undergo net inversion with predominant racemization in the phenolysis of (IIa). Variations in the yield and in the extent of retention for (Ib)–(IIIb) have been examined for various concentrations of added sodium phenoxide; variations in the optical rotation of recovered substrate and those in the extent of retention of the phenyl ether have also been determined in the course of each phenolysis. On the basis of this evidence, the mechanisms and steric courses of these reactions are discussed. Maximum rotations of the phenyl ethers (Ib)–(IIIb) and 1-arylethanols (Ic)–(IIIc) have been determined by chemical or n.m.r. shift reagent methods; the absolute configurations of (IIIb) and (IIIc) have also been assigned by the use of a chemical method.

Sex dependency of steroid retention in rat-liver slices incubated with testosterone.

The hepatic retention of steroids which occurs during the incubation of [4‐14C]testosterone with rat liver slices is demonstrated to be a sex‐specific phenomenon. After an incubation time of 30 min, slices from female animals can be shown to have retained significantly more [4‐14C] steroid than slices from male animals. The tissue/medium distribution ratio is 13 for the males and 30 for the females.Δ4‐5α‐Hydrogenase activity of the liver tissue can be regarded as the driving force for the retention of steroids derived from testosterone turnover. Namely, the steroid retention is positively correlated with the testosterone hydrogenation rate. The Δ4‐hydrogenating activity of the female exceeds that of the male by a factor of 1.73; this is the same factor by which the hepatic retention of the female exceeds that of the male.In contrast, there is an inverse correlation between the production rate of hydroxylated C19O2‐metabolites and the extent of retention. When compared to the female animal, slices from the male possess a higher hydroxylating activity accompanied by a much lower retention.The majority of metabolites isolated from tissue have a retention which is proportional to their production rate; however, the proportionality factor varies from metabolite to metabolite. Thus, for each individual metabolite, the slice is able to maintain a specific concentration gradient against the medium. For these metabolites the retention is sex‐specific only in so far as their production rate is sex‐specific.The retention of testosterone and androstenedione is independent of their production rate. They are found in the incubation medium of both sexes, but only in the tissue of males.

Radiochemical studies of chemisorption and catalysis: IX. The behavior of 14C-ethylene, 14C-propylene and tritium adsorbed on alumina- and silica-supported platinum catalysts

14C-Ethylene, 14C-propylene, and tritium tracer studies of the nature and reactivity of adsorbed species have been carried out between 20 and 350 °C, using alumina-and silica-supported platinum catalysts, at metal concentrations between 5 and 0.1% (w/w). The results show that with both ethylene and propylene a large fraction of the initially adsorbed material is retained by the catalyst as an unreactive strongly adsorbed species. The extent of retention is greater with ethylene than with propylene. Using tritium, it has been found that the support as well as the metal participates in the reaction, the degree of participation being greater with alumina than with silica. Evidence is presented to show that hydrogen migration between the metal and the support is of importance.