Retention Phenomena Research Articles

Protein adsorption dynamics to polymer surfaces revisited-A multisystems approach.

Performance and safety of materials in contact with living matter are determined by sequential and competitive protein adsorption. However, cause and consequences of these processes remain hard to be generalized and predicted. In a new attempt to address that challenge, the authors compared and analyzed the protein adsorption and displacement on various thoroughly characterized polymer substrates using a combination of surface-sensitive techniques. A multiple linear regression approach was applied to model the dependence of protein adsorption, desorption, and exchange dynamics on protein and surface characteristics. While the analysis confirmed that protein properties primarily govern the observed adsorption and retention phenomena and hydrophobicity as well as surface charge are the most relevant polymer surface properties, the authors have identified several protein-surface combinations that deviate from these patterns and deserve further investigation.

Evaluating air-water and NAPL-water interfacial adsorption and retention of Perfluorocarboxylic acids within the Vadose zone

The release and transport of linear perfluorocarboxylic acids (PFCA) within the vadose-zone beneath per- and polyfluoroalkyl substance (PFAS)- and non-aqueous phase liquid (NAPL)-contaminated source areas is influenced by multi-phase interfacial retention phenomena. Conceptually, interfacial adsorption results in retardation of PFCA velocities in subsurface multiphase systems. However, site hydrochemical factors influencing interfacial adsorption are not yet fully elucidated. Herein, air-water and NAPL-water interfacial tension isotherms were prepared for six homologous PFCAs of environmental significance for deionized water and five synthetic groundwaters of increasing ionic strength. The isotherms were successfully modeled by the Langmuir-Szyskowski equation and parameters used to fit the measured data are provided. Concentration-dependent interfacial adsorption coefficients and retardation factors are also provided for each PFCA and ionic strength condition and are evaluated to assess their significance. Simplifying relationships for predicting interfacial adsorption based on PFCA chain length were found to be less appropriate for natural groundwaters that contain a mixture of dissolved divalent and monovalent ions. Air-water interfacial (AWI) adsorption increased in a threshold manner with ionic strength from 0 to 6 mM, whereafter further adsorption was marginal. PFCA retention within water-unsaturated porous media is shown to depend on a number of inter-related factors and conditions that complicate the use of retardation factors within analytical models typically used for predicting transport rates under field conditions. Numerical simulation is thus necessary to model fundamental fate and transport processes. Mathematical relationships for incorporating interfacial adsorption in future and existing unsaturated flow and transport models are described.

Preliminary Investigations of the Feasibility of In-Vessel Melt Retention Strategies for a Small Modular Reactor Concept

The study presented in this paper is part of the technological surveillance performed at the Electricité De France (EDF) Research and Development (R&D) Center, in the Pericles department, and investigates the feasibility of modeling in-vessel melt retention (IVMR) phenomena for small modular reactors (SMR) with the modular accident analysis program version 5 in its EDF proprietary version (MAAP5_EDF), applying conservative hypotheses, such as constant decay heat after corium relocation to the lower head. The study takes advantage of a corium stratification model in the lower head of the vessel, developed by EDF R&D for large-sized prospective pressurized water reactors (PWRs). The analysis is based on a stepwise approach in order to evaluate the impact of various effects during IVMR conditions. First, an analytical calculation is performed in order to establish a reference case to which the MAAP5_EDF code results are compared. In a second step, the impact of the lower head geometry, vessel steel ablation, and subsequent relocation on the heat flux has been analyzed for cases where heat dissipation through radiation is neglected (in first approximation). Finally, the impact of heat losses through radiation as well as the crust formation around the pool has been assessed. The results demonstrate the applicability of the MAAP5_EDF code to SMRs, with heat fluxes lower than 1.1 MW/m2 for relevant cases, and identify modeling improvements.

The Influence of Compensation Management Strategy on Talent Retention: Exploring the Mediating Role of Structural Capital

Background: Retention of the employees is recognized as one of the significant problems of the present business world. The retention phenomena are observed to be impacted by the compensation practices employed by the firm.
 
 Objective: Based on this, the study aims to assess the compensation management strategies among Jordan commercial banks using structural capital approach.
 
 Methods: The study employed a quantitative design for assessing the employee retention. For this, data collection has been done using a survey based on a questionnaire.
 
 Results: The study has found a significant and positive impact of work life balance, satisfaction, and benefits on structural capital and talent retention. Moreover, the study failed to report a significant impact of salary on opportunity and job nature.
 
 Conclusion: The structure of the compensation management in the banking sector must encourage a new design for improving its impact intensity.

Experimental Design in Ion Chromatography: Effect of the Organic Modifier and Complexing Agent on the Retention of Alkaline and Alkaline Earth Ions

A Box–Behnken experimental design combined with response surface methodology was applied to investigate the effect of the eluent composition on the retention of common cations in ion chromatography. In particular, we modelled the retention factors of Na+, K+, NH4 +, Ca++ and Mg++ and the chromatogram resolution. Response surfaces were evaluated to assess interactive effects of nitric acid, pyridine-2,6-dicarboxylic acid and percentage of acetonitrile in the eluent on the above parameters. Nitric acid concentration and acetonitrile content appeared as the most and the least influential components of the eluent in determining the retention factors of individual ions or the global resolution of the chromatogram, while the concentration of the complexing agent exhibits an intermediate role. As expected, acidification of the mobile phase produces a decrease in the retention factors and a progressive worsening of resolution, and this effect can be modulated by the concentration of the complexing agent. The proposed approach seems suitable to investigate the retention phenomena in ion chromatography under application of complex eluent phases.

Adsorption and desorption kinetics and phosphorus hysteresis in highly weathered soil by stirred flow chamber experiments

Soils with a high weathering degree present great difficulties for management of phosphorus (P) fertilization due to their high adsorption rates. The magnitude and velocity of the P retention phenomena in these soils is still poorly understood and has great importance to effective management of soil phosphorus. The objective of this study was to evaluate the adsorption and desorption kinetics and phosphorus adsorption irreversibility (hysteresis) in highly weathered soils. For this purpose, we selected four soils: Xanthic Ferralsol-1 (FR-1), Xanthic Ferralsol-2 (FR-2), Rhodic Ferralsol (FR-3) and Hortic Anthrosol “Terra Preta de Índio” (AT). Adsorption followed by desorption experiments in Stirred flow chamber were performed. From obtained data, parameters related to P kinetics were estimated, considering the presence of two types of adsorption and desorption sites (fast and slow), estimating also the hysteresis index. It was observed that FR-2 and FR-3 showed higher P adsorption and most of the adsorbed P was at first 100min of evaluation. Furthermore, in FR-1, FR-2 and FR-3, approximately half of adsorption occurred by rapid sites (F which is the fraction of fast sites ranging from 0.45 to 0.55), while AT adsorption was lower (qmax=48.95mgkg−1) and occurred slower (F=0.33). In FR-2 and FR-3, between 71 and 72% of adsorbed P was not desorbed, while in AT, only 11% of P was irreversibly adsorbed. The P kinetics in highly weathered soils proved to be a process governed by the fast sites on adsorption and slow sites on desorption, resulting in high levels of hysteresis.

The effect of polymer size and charge of molecules on permeation through synovial membrane and accumulation in hyaline articular cartilage

The treatment of joint related diseases often involves direct intra-articular injections. For rational development of novel delivery systems with extended residence time in the joint, detailed understanding of transport and retention phenomena within the joint is mandatory. This work presents a systematic study on the in vitro permeation, penetration and accumulation of model polymers with differing charges and molecular weights in bovine joint tissue. Permeation experiments with bovine synovial membrane were performed with PEG polymers (6–200kDa) and methylene blue in customized diffusion chambers. For polyethylene glycol, 2-fold (PEG 6kDa), 3-fold (PEG 10kDa) and 13-fold (PEG 35kDa) retention by the synovial membrane in reference to the small molecule methylene blue was demonstrated. No PEG 200kDa was found in the acceptor in detectable amounts after 48h. This showed the potential for a distinct extension of joint residence times by increasing molecular weights.In addition, experiments with bovine cartilage tissue were conducted. The ability for positively charged, high molecular weight chitosans and HEMA-Co-TMAP (HCT) polymers (up to 233kDa) to distribute throughout the entire cartilage matrix was demonstrated. In contrast, a distribution into cartilage was not observed for neutral PEG polymers (6–200kDa). Furthermore, the positive charge density of different compounds (chitosan, HEMA-Co-TMAP, methylene blue, MSC C1 (neutral NCE) and MSC D1 (positively charged NCE) was found to correlate with their accumulation in bovine cartilage tissue.In summary, the results offer pre-clinical in vitro data, indicating that the modification of molecular size and charge of a substance has the potential to decelerate its clearance through the synovial membrane and to promote accumulation inside the cartilage matrix.

Tumoración en labio inferior: mucocele

Mucocele, also known as mucous retention phenomena, is a nodular-shaped swelling usually caused by trauma in the mucous membrane of the minor salivary glands.The oral cavity presents plenty of groups of mucous glands. Under normal conditions their ducts produce mucus on the surface and preserve a wet atmosphere for the mucous membrane.

Retention challenge facing Australia's rural community mental health services: Service managers' perspectives.

This paper aims to contribute to the development of a more sustainable Australian rural community mental health workforce by comparing the findings from a literature search investigating impacting factors on retention with the experiences of community mental health service managers running services in rural Australia. Semi-structured interviews. Public health sector, rural New South Wales. Five community mental health managers, running services in rural Australia. Interviews were undertaken as a pilot for a broader qualitative study investigating factors influencing the decision to stay or leave among community mental health professionals working in rural positions. The purpose of undertaking this pilot study was to test for validity and relevance of the retention phenomena and help inform the research design for the main study. Three key retention focussed themes were identified: (i) Staffing is a persistent challenge; (ii) Small remote towns pose the biggest challenge; and (iii) The decision to stay or leave is complex and multifactorial. The findings of this pilot study support previous research and contribute to the understanding of influences on retention among health professionals working in rural community mental health services. Importantly, those who have worked for several years in rural positions hold important information through which to explore factors that impact retention in rural and remote regions.

Distribution and partitioning of heavy metals in sediments of the Xinjiang River in Poyang Lake Region, China

Total metal concentrations were determined in top and historically subhorizon contaminated sediments collected from four sampling areas (Upstream (UP), Yongping Mining Area Stream (YP), Guixi Mining Area Stream (GX), and Downstream (DM)). The sediments were analyzed for Cu, Zn, Pb, Cd, Cr, As, and Ni using a sequential extraction scheme by Tessier. The results showed that the maximum values of Cu, Zn, and Pb were in top and subhorizon sediments collected from the YP areas, while the DM areas had the highest concentrations of Cd, Cr, As, and Ni. The majority of metal values were higher than the corresponding background values and were increasingly prevalent with the following order: Ni < Cr < Pb < Zn < Cd < As < Cu. Geoaccumulation Index indicated that the contamination degree ranged from uncontaminated to strongly contaminated. The comparison of total metal concentrations in top and subhorizon sediments at depth showed a large difference in the risk to biota. When metal partitioning characteristics were also considered, over 60% of metals were potentially bioavailable and likely toxic. By means of Hierarchical Cluster Analysis, a total number of four groups were distinguished from 16 sampling sites. Sediments from different sampling sites showed an apparent trend for grouping sites, which might be attributed to the various originations of heavy metals and the disturbance from human activities. Factor analysis results revealed two sources of pollutants, which can be explained by two factors: (i) mixed origin or retention phenomena of industrial emissions and (ii) terrigenous. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 713–723, 2015

ASTEC application for in-vessel melt retention modelling in VVER plants

The paper is devoted to extended ASTEC analyses of possible in-vessel retention (IVR) phenomena, based on simulation of main accident scenarios for VVER-1000 reactor design with the ASTEC 2.0 rev2 code. To reach the objective of the investigation, an assessment of two hypothetical low-pressure severe accidents scenarios has been carried out, which provided a basis for well-founded insight on key phenomena during IVR in a VVER-1000 plant. This examination allowed to obtain main characteristics of the corium that is relocated to lower plenum, along with necessary understanding of ex-vessel phenomena.Separate simulations of corium behaviour within the vessel lower head in conditions of external cooling show that the efficiency of IVR critically depends on residual nuclear power retained in the corium. Basing on calculation results it may be concluded that the IVR objective can be achieved for VVER-1000 at the level of residual power which corresponds to approximately 24h of accident transient after the initial event. Potentially such conditions can be realized on new Generation III plants or in the course of modernization of the existing ones by increasing water supply from passive safety injection tanks.A code-to-code comparison between ASTEC and the SOCRAT Russian code confirms main results obtained. At the same time it revealed certain deficiencies in existing modelling approaches, which are the result of poorly examined thermodynamical properties of the corium at temperatures higher than 2200K.

Impact of Must Sugar Reduction by Membrane Applications on Volatile Composition of Verdejo Wines

Climate changes are inducing increased sugar levels of must, which produces negative effects on wine quality, as unbalanced wines with high degrees of alcohol. So, effective strategies to control the increase of sugar levels in must have been studied. One of them is the use of a membrane process, and this is applied in this work. The sugar level of white must from Verdejo (Vitis vinifera variety) was reduced using diverse membrane processes, and the effect of this fact on the volatile composition of the corresponding wines is studied. The study was carried out during three consecutive vintages. An important impact of the reduction of sugar levels of must on the volatile composition of the obtained wines was detected, which was due to some retention phenomena of aromatic and precursor compounds. To minimize the volatile composition modifications, an appropriate selection of the nanofiltration membrane must be done.

Upgrading of the micro-marsupialisation technique for the management of mucus extravasation or retention phenomena

This study evaluated the performance of an upgrading of the micro-marsupialisation technique for the management of mucus extravasation or retention phenomena. This study presents a prospective case series of management of ranulas and mucoceles, with a follow-up ranging from 6 to 18 months. Data included the age and gender of patients, as well as the type, size, and site of lesions, and number of punctures. The treatment performance was evaluated according to: postoperative pain, oedema, secondary infection, clinical healing, retreatment, and recurrence of the lesions. All patients showed clinical healing of the lesions within 30 days after the micro-marsupialisation technique. None of patients presented a recurrence or required retreatment, there was no oedema or infection. No pain, or mild pain was reported by the majority of patients (58.81%). Micro-marsupialisation proved to be a simple, low cost, relatively non-invasive, painless, effective, and low recurrence technique to treat mucus extravasation or retention phenomena. Micro-marsupialisation can be recommended primarily to treat oral ranulas and selected mucoceles.

A Simple Model to Assess Nitrogen and Phosphorus Contamination in Ungauged Surface Drainage Networks: Application to the Massaciuccoli Lake Catchment, Italy

Modeling is a common practice to evaluate factors affecting water quality in environmental systems impaired by point and nonpoint losses of N and P. Nevertheless, in situations with inadequate information, such as ungauged basins, a balance between model complexity and data availability is necessary. In this paper, we applied a simplified analytical model to an artificially drained floodplain in central-western Italy to evaluate the importance of different nutrient sources and in-stream retention processes and to identify critical source areas. We first considered only a set of chemical concentrations in water measured from February through May 2008 and from November 2008 through February 2009. We then broadened available data to include water discharge and hydraulic-head measurements to construct a hydrogeological model using MODFLOW-2000 and to evaluate the reliability of the simplified method. The simplified model provided acceptable estimates of discharge (ranging from 0.03-0.75 m s) and diffuse nutrient inputs from water table discharge and in-stream retention phenomena. Estimates of PO-P and total P retention (ranging from 1.0 to 0.6 μg m s and from 1.18 to 0.95 μg m s for PO-P and total P, respectively) were consistent with the range of variability in literature data. In contrast, the higher temporal variability of nitrate concentrations decreased model accuracy, suggesting the need for more intensive monitoring. The model also separated the dynamics of different reaches of the drainage network and identified zones considered critical source areas and buffer zones where pollutant transport is reduced.

Comparison of multiple linear regression, partial least squares and artificial neural network for quantitative structure retention relationships of some polycyclic aromatic hydrocarbons

Quantitative structural-retention relationships (QSRR) of retention phenomena of polycyclic aromatic hydrocarbons (PAHs) facilitate resolving complex mixtures of them by gas chromatography (GC). The structural descriptors of 38 PAH compounds were calculated. Stepwise variable selection was applied for selection of meaningful descriptors. MLR, PLS and ANN models were built with calibration compounds. The predictive ability of the models was evaluated on 6 PAHs, which were not used in training steps and also by leave-6-out cross-validation. The best prediction results were obtained by the MLR model. The difference in predictive ability of the ANN and PLS model was trivial.

Charge retention phenomena in CT silicon nitride: Impact of technology and operating conditions

The aim of this work is to understand charge loss mechanisms in TANOS stack for which charge retention is monitored just after programming in an almost continuous way and voltage is applied during retention experiments in order to obtain zero electric field either on alumina or tunnel oxide. The charge loss mechanisms in TANOS stack can be a quite complicated process: An initial fast DT from interface traps localized at SiN/alumina interface, followed by charge loss through alumina from bulk traps in SiN which influences charge redistribution towards the tunnel oxide, observed only in Si-rich SiN. Programming voltage and stack composition impact trapped charge localization and hence charge redistribution and charge loss, even if the same initial Vfb is considered in charge retention experiments. While the charge loss through tunnel oxide is a DT, the charge loss through alumina depends on temperature and it is the main component of the charge loss in retention experiments for longer time.

Aerosol retention in the flooded steam generator bundle during SGTR

A steam generator tube rupture in a pressurized water reactor may cause accidental release of radioactive particles into the environment. Its specific significance is in its potential to bypass the containment thereby providing a direct pathway of the radioactivity from the primary circuit to the environment. Under certain severe accident scenarios, the steam generator bundle may be flooded with water. In addition, some severe accident management procedures are designed to minimize the release of radioactivity into the environment by flooding the defective steam generator secondary side with water when the steam generator has dried out. To extend our understanding of the particle retention phenomena in the flooded steam generator bundle, tests were conducted in the ARTIST and ARTIST II programs to determine the effect of different parameters on particle retention. The effects of particle type (spherical or agglomerate), particle size, gas mass flow rate, and the break submergence on particle retention were investigated. Results can be summarized as follows: increasing particle inertia was found to increase retention in the flooded bundle. Particle shape, i.e., agglomerate or spherical structure, did not affect retention significantly. Even with a very low submergence, 0.3 m above the tube break, significant aerosol retention took place underlining the importance of the jet–bundle interactions close to the tube break. Droplets were entrained from the water surface with high gas flow rates carrying aerosol particles with them. However, compared to particle retention in the water close to the tube break, the effect of droplet entrainment on particle transport was small.

Development of suction measurement techniques to quantify the water retention behaviour of GCLs

ABSTRACT: Geosynthetic clay liners (GCLs) have the potential to act as excellent hydraulic barriers, and have been successfully used in numerous barrier system applications, including composite landfill liners. In order to function effectively in the role of a hydraulic barrier, these products must first hydrate through the uptake of moisture from the subsoil. They then must demonstrate adequate dimensional stability during any subsequent moisture loss, to avoid separation of the panel overlaps. The key to understanding these moisture uptake and retention phenomena is the constitutive relationship between suction and moisture content. This relationship is commonly referred to as the water retention curve (WRC) of a material. Despite the significance of this relationship for the final success of the barrier, only a few studies have successfully quantified portions of water retention curves, and for only a subset of available GCL product types. This scarcity of data is due primarily to the inherent difficulty of determining this function experimentally for a composite material such as a GCL, and to the difficulty in measuring the wide range of suctions that need to be investigated. In response to this data gap, a dual-technique strategy for the quantification of WRC for GCLs is investigated in this paper, in which two different suction measurement techniques (high-capacity tensiometers and capacitive relative humidity sensors) have been assessed to see whether they are capable of experimentally quantifying the relationship between moisture content and suction for a GCL. This paper discusses the sample preparation techniques and required equilibration times for these techniques, and demonstrates that they can provide water retention data for GCLs that are consistent with published results.

Transport of CO2-Foaming Agents During CO2-Foam Processes in Fractured Chalk Rock

Summary The coinjection of carbon dioxide (CO2) and a CO2-foaming agent to form stable CO2 foam has been found to improve the sweep efficiency during CO2-foam processes in carbonate reservoirs. However, only a few studies of CO2-foam transport in fractured rock have been reported. In fractured chalk reservoirs with low matrix permeability, the aqueous CO2-foaming-agent solution will flow mainly through the fractures. The total retention of the CO2-foaming agent in the reservoir will depend on how much of the matrix is contacted by the CO2-foaming-agent solution during the project period and, therefore, on its transport rate into the matrix. This paper presents results from a series of static and flowthrough experiments carried out to investigate the transport and retention phenomena of CO2-foaming agents in fractured chalk models at 55°C. Fractured chalk models with 100% water-saturation and residual-oil saturation after waterflooding were used. In the static experiments, the fractured model was created by transferring core plugs with different diameters into steel cells with an annulus space around the plugs. The fracture volume was filled with foaming-agent solutions with different initial concentrations. The experiments were carried out in parallel, with liquid samples regularly taken out from the fracture above the plugs and analyzed for the foaming-agent concentration. The experiments were monitored until the concentrations in the fractures reached a plateau. At specific and constant concentrations of the foaming agent in the fractures, the plugs were demounted and samples drilled out along the whole lengths of the plugs from the outer, middle, and center portions. These samples were analyzed for foaming-agent concentration to determine how much of it had penetrated the matrix. Results indicate that the transport of the foaming-agent decreases toward the center of the plugs with 100% water-saturation and residual-oil saturation after waterflooding. Modeling of the static experiments using the Computer Modelling Group (CMG)'s commercial reservoir simulator STARS was also carried out to determine the transport rate for the foaming agent. A good history match between experimental and modeling results was obtained. In the flow-through experiments, the fractured model was created by drilling a concentric hole through the center of the plug. The hole, simulating an artificial fracture, was filled with glass beads of different dimensions. Fractured models with different effective permeability were flooded with equal volumes of the foaming-agent solution. Results show that the transport of CO2-foaming agent into the matrix is slower in the fractured models than in the homogeneous models with viscous flooding of the rock.

Mucus extravasation and retention phenomena: a 24-year study

BackgroundMucoceles are benign lesions related to the minor salivary glands and their respective ducts frequently affecting oral structures which are generally asymptomatic. Mucoceles are generally characterized by swollen nodular lesions preferentially located on the lower lip and differ from the so-called ranulas, which are lesions located on the floor of the mouth and related to the sublingual or submandibular glands.MethodsThe objective of the present study was to analyze data such as age, gender, race and site of the lesion of 173 mucocele cases diagnosed at the Discipline of Stomatology, São José dos Campos Dental School, UNESP, over a period of 24 years (April 1980 to February 2003).ResultsOf the 173 cases analyzed, 104 (60.12%) were females and 69 (39.88%) were males. Age ranged from 4 to 70 years (mean ± SD: 17 ± 9.53) and most patients were in the second decade of life (n = 86, 49.42%); white (n = 124, 71.68%). The lower lip was the site most frequently affected by the lesions (n = 135, 78.03%), whereas the lowest prevalence was observed for the soft palate, buccal mucosa, and lingual frenum.ConclusionIn this study, mucoceles predominated in white female subjects in the second decade of life, with the lower lip being the most frequently affected site.