Undesirable Migration Research Articles

Differentiation of Regions According to the Standard of Living of the Population

The relevance of this work is determined by the important problems of improving living standards in Russia, increasing the welfare of the population, and reducing poverty. High differentiation of the country’s regions also creates additional risks associated with forming undesirable migration flows of both population and business. Studies show that while being a leader in one area, a region may lag in other areas. It is necessary to determine how interrelated the various indicators of living standards in the subjects of the Russian Federation are. The research methods are based on the analysis of indicators of living standards of the population of Russian regions. In particular, the authors analyzed current and retrospective values, compared the values of indicators in different regions of the country, correlation and cluster analysis. The study formed integral indicators of regional development in five areas that characterize the population’s living standard to carry out calculations. The analysis results showed that there is no significant linear correlation between 22 selected private indicators of living standards in the vast majority of cases. The prospects of the study lie in further identification of ways to improve the situation, considering the specifics of the ratio of various indicators of living standards.

Porous Ionic Network/CNT Composite Separator as a Polysulfide Snaring Shield for High Performance Lithium-Sulfur Battery.

Lithium-sulfur (Li-S) battery features a high theoretical energy density, but the shuttle of soluble polysulfides between the two electrodes often results in a rapid capacity decay. Herein, a straightforward electrostatic adsorption strategy based on a cross-linked polyimidazolium separator as a snaring shield of polysulfides is reported, which suppresses the undesirable migration of polysulfides to the anode. The porous ionic network (PIN)-modified carbon nanotubes (CNTs) are successfully prepared and coated onto a commercial porous polypropylene membrane in a vacuum-filtration step. The favorable affinity of the imidazolium ring toward polysulfide via the polar interaction and the electrostatic effect of ions mitigates the undesirable shuttle of polysulfides in the electrolyte, improving the Li─S battery in terms of rate performance and cycling life. Compared to the reference PIN-free CNT-coated separator, the PIN/CNT-coated one has an increased initial capacity of 1.3 folds (up to 1394.8mAhg-1 for PIN/CNT/PP-3) at 0.1C.

Beyond Rattling: Tetrahedrites as Incipient Ionic Conductors.

Materials with ultralow thermal conductivity are crucial to many technological applications, including thermoelectric energy harvesting, thermal barrier coatings, and optoelectronics. Liquid-like mobile ions are effective at disrupting phonon propagation, hence suppressing thermal conduction. However, high ionic mobility leads to the degradation of liquid-like thermoelectric materials under operating conditions due to ion migration and metal deposition at the cathode, hindering their practical application. Here, a new type of behavior, incipient ionic conduction, which leads to ultralow thermal conductivity, while overcoming the issues of degradation inherent in liquid-like materials, is identified. Using neutron spectroscopy and molecular dynamics (MD) simulations, it is demonstrated that in tetrahedrite, an established thermoelectric material with a remarkably low thermal conductivity, copper ions,although mobile above 200 K, are predominantly confined to cages within the crystal structure. Hence the undesirable migration of cations to the cathode can be avoided. These findings unveil a new approach for the design of materials with ultralow thermal conductivity, by exploring systems in which incipient ionic conduction may be present.

Treatment of carbocysteine wastewater by bipolar membrane electrodialysis: From lab-to pilot-scale

Carbocysteine (H2ccys) wastewater, which contains H2ccys, chloroacetic acid, and ammonium chloride, can pose significant risks to the environment. In this study, a novel strategy was proposed for treating H2ccys wastewater by bipolar membrane electrodialysis (BMED) to realize resource recovery. The migration and coexistence mechanism of organic/inorganic ions in wastewater were investigated in lab-scale experiments. The results indicated that the desirable migration of inorganic ions, such as NH4+ and Cl− ions, in the feed compartment were dominant. The undesirable migration of organic molecules, such as ClCH2COOH and H2ccys, could be managed through precise control of the BMED reaction process. To optimize the energy efficiency and thermal effect occurred in the pilot-scale, a two-stage BMED process was designed for treating H2ccys wastewater. The results revealed that BMED produced 1.33–1.63 M of HCl and 2.62–2.88 M of NH3·H2O, and removed 90 wt% of NH4Cl from H2ccys wastewater. Meanwhile, the thermal effect of the slot at the outermost acid compartment decreased from 3.32 W in the one-stage BMED process to 0.10 W in the two-stage BMED process during the pilot-scale tests. The current efficiency of the two-stage BMED process for the acid/base production and feed desalination in the pilot-scale tests increased and its energy consumption decreased compared with the lab-scale tests. Moreover, the BMED rrecycling route showed that a closed loop can be realized in the treatment of H2ccys wastewater, and its economic assessment showed that applying BMED to the treatment of H2ccys wastewater have economic benefits. These findings illustrated the feasibility of this novel strategy for treating H2ccys wastewater and laid a solid foundation for its industrialization.

From Undesirable Immigrants to Prosperous Merchants: Chinese and Palestinians in Southern Peru (1900s–1930s)

ABSTRACT The article analyses the commercial trajectory of Chinese and Palestinian immigrants, the largest communities in the cities of Arequipa and Moquegua in southern Peru. Although they were not part of ‘desired’ immigration projects and faced a series of prejudices and hostilities, these immigrants integrated significantly into the regional and national economies. The article draws on the qualitative analysis of a heterogeneous set of primary archival sources, many of which have not been studied before. These sources include records of immigration up to 1931, notarial files, and press reports from both cities. This work contributes to migration and business studies based on two approaches: undesirable migration and the role of migrants in forming the modern business system of the countries of the region.

Nanoparticles of metals and their compounds in films and coatings: A review

Nanotechnology is important in food packaging because it increases shelf life, enhances food safety, and improves sensory characteristics and nutrient availability. We aimed to review scientific publications on the synthesis of nanoparticles, as well as their properties and applications in the food industry.
 Research and review articles published from 2020 to 2022 were obtained from the database using the keywords “nanoparticles”, “film”, and “food”. They were on the synthesis of metal and metal oxide nanoparticles and their uses in food films and coatings. 
 We reviewed methods for synthesizing inorganic nanoparticles from metals and their compounds (silver, zinc, iron, etc.), as well as described their antimicrobial action against foodborne pathogens. By incorporating nanoparticles into films, we can create new materials with strong antimicrobial properties in vitro. Nanoparticles can be used to develop both polymer and biopolymer films, as well as their mixtures. Composite coatings can work synergistically with metal nanoparticles to create multifunctional food packaging systems that can act as compatibilizers. Particular attention was paid to metal nanoparticles in food coatings. We found that nanoparticles reduce the rate of microbial spoilage and inhibit lipid oxidation, thereby increasing the shelf life of raw materials and ready-to-eat foods. The safety of using nanoparticles in food coatings is an important concern. Therefore, we also considered the migration of nanoparticles from the coating into the food product.
 Incorporating nanoparticles into polymer and biopolymer films can create new materials with antimicrobial properties against foodborne pathogens. Such composite films can effectively extend the shelf life of food products. However, the undesirable migration of metal ions into the food product may limit the use of such films.

Global patterns of water‐driven human migration

AbstractEnvironmental change is growingly reported as an important driver of human migration. Among all environmental variables, water crises are the most critical factors. To date, patterns of interconnections between changes in water and migration are not yet clearly understood. Here, we explore these patterns through a systematic review that combined a quantitative text‐mining approach with qualitative thematic analysis. Our results generally concur with those of previous studies, which found that water‐driven migration usually occurs internally and that the population in low‐ and middle‐income countries and in dry regions are the most vulnerable and more likely to migrate or be displaced in the face of water‐related events. However, our causal network analysis highlights that water is not the only reason for migration: Its related problems could be major triggers driving people‐at‐risk to leave their original place. Based on observed evidence, water‐driven migration can be generally divided into four patterns: variability in water quantity, damaging water hazards and extremes, physical disturbances to water systems, and water pollution. These patterns are not independent but interconnected through multifaceted factors affecting people's livelihoods and their decisions to migrate. Understanding water‐migration dynamics requires systematic thinking of the interconnections between changes in water and in migration patterns, the investigation of interactions between fast and slow water variables and their dynamic link to other socioeconomic variables, an integrated water‐migration database to help identify early‐warning signals of damaging water hazards that may result in undesirable migration, and targeted water policies that focus on building the resilience of vulnerable regions and population to climate change.This article is categorized under: Human Water > Value of Water

Al-doped Nb2O5/carbon micro-particles anodes for high rate lithium-ion batteries

Orthorhombic niobium pentoxide (T-Nb2O5) has attracted extensive attention in the field of ultra-fast lithium ion batteries (LIBs) due to its high rate performance. However, its instability at a low potential and inherent low conductivity limits its fast charging capability. Here, microspheres of aluminum-doped T-Nb2O5 embedded in N-doped carbon network (Al-Nb2O5@NC) are prepared. The effects of Al-doping on the crystal structure and electrochemical properties are systematically studied. It is found that Al-doping has led to increase of the density of O2− vacancies and low-oxidized state Nb4+ ions, improving ionic and electrical conductivity. The substitution of Al3+ ions for Nb5+ions improves the lattice stability, reduces the undesirable migration of Nb in cycling, and stabilizes the capacity during fast charging. The LIBs using Al-Nb2O5@NC as anode have high rate performance and cycling stability (i.e., ∼82 mAh g−1 at 20 A g−1 after 9900 cycles). Meanwhile, the intercalation-type electrochemical reaction is verified by in-situ transmission electron microscope (TEM), by which it is found that Al-Nb2O5@NC has better crystalline integrity. By integrating Al doping and carbon network, the micron-size Al-Nb2O5@NC particles developed in this work are promising anodes to build fast charge/discharge LIBs with high specific capacity, stability and excellent rate performance.

Development of High-Performance Non-Foaming Cationic Soap-Washing Agent through the Copolymerization of N-Vinylpyrrolidone with 2-(Dimethyalamino) Ethyl Methacrylate for Wash-off Reactive Dyed Cotton Fabric

Reactive dyes are generally used for the coloration of cotton fabric. However, hydrolyzed/unfixed dyes are generated and fail to react with fibers, which are responsible for decreasing the colorfastness and creating undesirable color migration among fabrics during washing. So, after dyeing is finished, an effective wash should be carried out to remove additional and unfixed dyes with an effective soap-washing agent. Thus, the soap-washing agent plays a significant role during wash-off and also can avoid undesirable effects such as colorfastness, shade variation, stains, etc. Hence, in this article, a series of cationic soap-washing agents were prepared by copolymerizing N-vinylpyrrolidone with DMAEMA, and the working efficiencies were evaluated. All the samples were washed using different soap-washing agents for 30 minutes under 90? temperatures. It was found that the pH factor greatly influences the unfixed dye removal efficiencies in washing liquors and the concentration of the soap-washing agent. The best washing result for removing unfixed dyes was obtained for V/D5/SDS2 soap-washing agent for 1g/L at pH 7 in liquors. The soap-washing agent effectively removes unfixed dye and can prevent color migration among fabrics during wash-off. The characteristics were analyzed by Data color650 spectrophotometer, UV-visible spectrophotometer, Dry and wet rubbing fastness, and Fourier Transform Infrared Spectroscopy (FTIR).

Encapsulin Based Self-Assembling Iron-Containing Protein Nanoparticles for Stem Cells MRI Visualization

Over the past decade, cell therapy has found many applications in the treatment of different diseases. Some of the cells already used in clinical practice include stem cells and CAR-T cells. Compared with traditional drugs, living cells are much more complicated systems that must be strictly controlled to avoid undesirable migration, differentiation, or proliferation. One of the approaches used to prevent such side effects involves monitoring cell distribution in the human body by any noninvasive technique, such as magnetic resonance imaging (MRI). Long-term tracking of stem cells with artificial magnetic labels, such as magnetic nanoparticles, is quite problematic because such labels can affect the metabolic process and cell viability. Additionally, the concentration of exogenous labels will decrease during cell division, leading to a corresponding decrease in signal intensity. In the current work, we present a new type of genetically encoded label based on encapsulin from Myxococcus xanthus bacteria, stably expressed in human mesenchymal stem cells (MSCs) and coexpressed with ferroxidase as a cargo protein for nanoparticles’ synthesis inside encapsulin shells. mZip14 protein was expressed for the enhancement of iron transport into the cell. Together, these three proteins led to the synthesis of iron-containing nanoparticles in mesenchymal stem cells—without affecting cell viability—and increased contrast properties of MSCs in MRI.

Gross regional product: study of influencers

The relevance of the research topic is determined by special attention to issues of regional development in the state policy of the Republic of Belarus, the quality of life of 78.6% of the country's population depends on the level of development of the regions under study. The problem of regional development is the growing imbalances in development between the regions of the country and, as a result, undesirable interregional migration flows of the population and a reduction in the demographic potential of a number of territories, as well as the emergence of signs of depression in a number of areas. The analysis of recent publications makes it possible to verify an ongoing interest in the issue, but the drawback of most studies is the disclosure of the issue within one particular region, or the study of the growth of grp due to conventional factors. According to the authors, until the end of the unexplored, the dependence of the gross regional product on indirect, implicit factors remains. Particular attention is drawn to the author's indicators and their place in the GRP growth model. The aim of the study is to establish the influence of unconditional and indirect factors on the magnitude and dynamics of gross regional product, which will provide an opportunity to formalize the dependence of grp on these factors and subsequently apply the built model in practice. The study methods used in the work are comparison, grouping, correlation-regression analysis, econometric modeling, and a systemic approach. Results of work. The present study considers a set of indicators for six regions of the republic of belarus for the period from 2013 to 2019. Using econometric methods of analysis, the authors built a regression model of the dependence of grp per capita on four exogenous variables, analyzed the degree of influence of these variables and the possibility of impact on them by the state. The area of application of the study results is state policy aimed at the sustainable growth of the economies of the regions. Conclusions. In the constructed model of four exogenous variables, the unemployment rate and the rate of life of the population are most significant. However, according to the authors, in order to achieve the desired level of gross regional product, it is necessary to have a comprehensive impact on all variable models, among which, in descending order of importance, the level of unemployment, the rate of life of the population, the amount of industrial production per person employed in the economy, investment in fixed assets.

Precision Embolism: Biocompatible Temperature‐Sensitive Hydrogels as Novel Embolic Materials for Both Mainstream and Peripheral Vessels

AbstractComplete blood blockage and low ectopic embolism risk are urgently needed for transcatheter arterial chemoembolization (TACE) treatment. However, the clinically available embolic reagents still face the huge challenges of fast recanalization and undesirable migration. In the present work, a temperature‐sensitive poloxamer 407 (F127)/hydroxymethyl cellulose (HPMC)/sodium alginate (SA)‐derived hydrogel (FHSgel) is explored as a novel embolic material in the TACE treatment. With increasing temperature, this FHSgel undergoes sensitive phase transition process, so as to block both mainstream and peripheral vessels. Meanwhile, taking advantage of the close fitness between shapeable FHSgel and vessels, the embolism time is extremely extended. Moreover, the leaked FHSgel could be diluted below the gelation concentration, thus effectively preventing from ectopic embolism. TACE treatment is further conducted for rabbit liver and kidney tumors, wherein the atrophic blood vessels and necrotic tissue demonstrate superior therapy effect. In addition, all three pharmaceutical excipients are approved by the Food and Drug Administration (FDA). In contrast with the clinical embolic reagents, the temperature‐sensitive FHSgel for the first time completely blocks both mainstream and peripheral vessels with totally biocompatible pharmaceutical excipients, and makes a breakthrough in terms of largely reducing the ectopic embolism risk, thus providing a new generation for interventional embolization.

Migration and Stabilization of Radical Scavengers in PEFCs

Cerium ions are additives which enhance the durability of polymer electrolyte fuel cells (PEFCs) by scavenging reactive radical species which are generated during operation.1 These radicals attack vulnerable carboxyl, sulfonic acid, and ether groups in the ion conducting polymer, or ionomer, phases in the polymer electrolyte membrane (PEM) and catalyst layers (CLs) within the membrane electrode assembly (MEA) of the cell.2 During cell fabrication, conditioning, and discharge, Ce rapidly migrates between the PEM and CLs, which reduces efficiency of the Pt catalyst and may negate the addition of the Ce additive.3,4 Therefore, in order to stabilize Ce and localize it to areas of highest radical generation, it is critical to understand the relative influences of different migration mechanisms. In this work, we identified the fundamental Ce migration mechanisms during PEM fuel cell operation. Using a novel elemental analysis technique based on X-ray fluorescence (XRF), we characterized Ce migration due to potential and concentration gradients, water flux, and degradation of Ce-exchanged sulfonic acid groups within the PEM. During accelerated stress tests (ASTs), which are designed to reproduce and enhance stressors the cell will experience in the field, we have observed that < 1% of Ce exits the cell during open circuit voltage (OCV) between 30% and 100% RH. It does, however, irreversibly migrate from the PEM into the CLs at a rate correlated to AST aggressiveness. As a result, Ce accumulation in the CL reduces performance, while Ce migration out of the PEM lowers the PEM’s ability to resist the harmful effects of reactive radicals. In order to determine the relevant Ce transport coefficients during cell operation, Ce migration was induced in PEMs using H2 pump experiments under a range of applied potentials at 50% and 100% RH. Ce profiles were intermittently measured using XRF and fit with a 1-D Nernst-Planck equation. Using this model, diffusion and ion mobility coefficients were extracted, which arise due to concentration and potential gradients during the H2 pump experiments, respectively. The results show the rapid and significant effects of such gradients on Ce movement. Using this knowledge, we propose system control and additional material engineering strategies to mitigate Ce migration due to potential and concentration gradients, in order to reduce performance losses and improve cell durability. We have also determined that the degradation of Ce-exchanged ionomer side chains during aggressive ASTs results in significant Ce migration from the PEM into the CLs. In order to counter undesirable migration due to ionomer degradation, we propose the use of more efficient radical scavengers or improved localization of scavengers near areas of highest radical generation. Zirconia-doped ceria (CZO) has previously been shown to enhance peroxide reactivity while minimizing byproduct radical generation.5 We have demonstrated that adding CZO to the cathode CL, where significant peroxide and radical generation occurs6,7, results in identical initial cell polarization performance compared to CZO-free cells. During PEM chemical stability ASTs, however, CZO reduces gas crossover (Figure 1a) and fluoride emission (Figure 1b) rates, which implies that it is a more effective radical scavenger. Less ionomer degradation results in stable performance of the CZO-enhanced MEA after 500 hours of ASTs. Furthermore, after >1400 hours of ASTs, the Ce concentration in the PEM was maintained at its initial value due to the protective capabilities of CZO. Acknowledgements This research is supported by the U.S. DOE Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability (FC-PAD) Consortium; Fuel Cells Program manager: Dimitrios Papageorgopoulos. Prof. Ajay Prasad and Prof. Suresh Advani also acknowledge support from the University of Delaware’s Fuel Cell Bus Program. This program is funded by the Federal Transit Administration at the Center for Fuel Cell Research at the University of Delaware. References Coms, F. D.; Liu, H.; Owejan, J. E. ECS Trans. 16, 1735–1747 (2008).Rodgers, M. P.; Bonville, L. J.; Kunz, H. R.; Slattery, D. K.; Fenton, J. M. Chem. Rev. 112, 6075–6103 (2012).Stewart, S. M.; Spernjak, D.; Borup, R.; Datye, A.; Garzon, F. ECS Electrochem. Lett. 3, F19–F22 (2014).Baker, A. M.; Mukundan, R.; Spernjak, D.; Judge, E. J.; Advani, S. G.; Prasad, A. K.; Borup, R. L. J. Electrochem. Soc. 163, F1023–F1031 (2016).Stewart, S. M.; Borup, R. L.; Wilson, M. S.; Datye, A.; Garzon, F. H. ECS Trans. 64, 403–411 (2014).Sethuraman, V. A; Weidner, J. W.; Haug, A. T.; Motupally, S.; Protsailo, L. V. J. Electrochem. Soc. 155, B50-B57 (2008).Gubler, L.; Dockheer, S. M.; Koppenol, W. H. J. Electrochem. Soc. 158, B755-B769 (2011). Figure 1

Application of geocomposite placed beneath ballast bed to improve ballast quality and track stability

The article deals with the application of a stabilization hexagonal geocomposite for the improvement of poor stability of railway tracks caused by undesirable migration of fine soil particles from the subgrade into the ballast bed. The establishment of a test railway section on a single-line track situated near Domazlice and its long-term monitoring programme are described. Evaluation is aimed especially at track geometry parameters, the load-bearing capacity of the ballast bed, elastic rail deflection during train passages and the durability of geocomposite’s physical properties. The data taken from the test section during five measurement campaigns are compared with both adjacent sections. In one of them, only the ballast bed renovation was carried out, whereas in the second one no intervention was performed at all. The usage of a pioneering geosynthetic product in combination with new trends in ballast bed restoration seems to be an innovative as well as effective solution to analogous problematic spots on railway tracks in the Czech Republic.

Sharing the Risks and Rewards of Economic Migration

International cooperation on economic migration has been difficult to achieve. The interests of emigration countries (“source countries”) and immigration countries (“destination countries”) seem impossible to align. These countries disagree on who should migrate: source countries resist migration that leads to a brain drain, while destination countries welcome these very migrants given that they are likely to be the most productive citizens and the least likely to become fiscal burdens on the destination country. In addition, destination countries resist migration that leads to domestic unemployment through labor replacement. As a result, international economic migration remains restricted at a substantial cost to world welfare. This Article argues that the global welfare gains from migration can be divided in a way that makes all stakeholders better off. It develops the idea of a “Migration Fund” that is used to insure the destination country against fiscally induced or otherwise undesirable migration while simultaneously serving as a mechanism to compensate the source country for the potential adverse effects of outward migration. As a condition for entry, the migrant or his sponsor deposits funds in a Migration Fund. If the migrant subsequently becomes unemployed or otherwise unable to support himself, this Fund will reimburse the destination country for the welfare benefits the migrant draws. Alternatively, the Fund would cover the costs of the migrant’s possible voluntary repatriation or, when warranted, deportation. This way, the Fund removes the concern that the migrant imposes a cost on the destination country. However, if the migrant remains employed and hence continues to contribute to the welfare of the

Vegetal fiber‐based biocomposites: Which stakes for food packaging applications?

ABSTRACTConsidering the needs of designing suitable food packaging that is able to decrease food losses while reducing the overall environmental impact of the food/packaging system, full biocomposites, i.e., both biodegradable and bio‐sourced, are becoming serious candidates for food packaging applications. This article aims at reviewing the knowledge about the functional properties of vegetal fibers‐based biocomposites, by considering the specific stakes relative to the food packaging application, i.e., the targeted functional properties, including mechanical properties and mass transfer properties (especially the permeability toward O2, CO2, and water vapor), the processability of materials using conventional equipments, the economical competitiveness, and the food safety. The first part summarizes the main characteristics of the constituents, i.e., matrices and fillers, and the processing routes to prepare biocomposites. In the second part, the ways to better understand and control the mass transfer properties in biocomposites will be deciphered by reminding the role of mass transfers in the food/packaging system and by focusing on how mass transfer properties are impacted by the material structure and mechanical properties. Food safety aspects will also be considered, by highlighting the possible undesirable migration from biocomposites toward food. This review will conclude on the main bottlenecks that should be resolved in order to make the use of biocomposites more viable for food packaging applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42528.

SU‐E‐T‐717: Surface Coating for Prevention of Metallic Seed Migration in Tissues

Purpose:In radiotherapy, metallic implants often detach from their deposited sites and migrate to other locations. This undesirable migration could cause inadequate dose coverage for permanent brachytherapy and difficulties in image‐guided radiation delivery for patients. To prevent migration of implanted seeds, we propose a potential strategy to use of a biocompatible and tissue‐adhesive material called polydopamine.Methods:In this study, non‐radioactive dummy seeds that have the same geometry and composition as commercial I‐125 seeds were coated in polydopamine. Using scanning electron microscopy and X‐ray photoelectron spectroscopy, the surface of the polydopamine‐coated and non‐coated seeds was characterized. The detachment stress between the two types of seeds and the tissue was measured. The efficacy of polydopamine‐coated seed was investigated through in‐vitro migration tests by tracing the seed location after tissue implantation and shaking for given times. The cytotoxicity of the polydopamine coating was also evaluated.Results:The results of the coating characterization have shown that polydopamine was successfully coated on the surface of the seeds. In the adhesion test, the polydopamine‐coated seeds had 2.1‐fold greater detachment stress than non‐coated seeds. From the in‐vitro test, it was determined that the polydopamine‐coated seed migrated shorter distances than the non‐coated seed. This difference was increased with a greater length of time after implantation.Conclusion:We suggest that polydopamine coating is an effective technique to prevent migration of implanted seeds, especially for permanent prostate brachytherapy.

Surface coating for prevention of metallic seed migration in tissues.

In radiotherapy, metallic implants often detach from their deposited sites and migrate to other locations. This undesirable migration could cause inadequate dose coverage for permanent brachytherapy and difficulties in image-guided radiation delivery for patients. To prevent migration of implanted seeds, the authors propose a potential strategy to use a biocompatible and tissue-adhesive material called polydopamine. In this study, nonradioactive dummy seeds that have the same geometry and composition as commercial I-125 seeds were coated in polydopamine. Using scanning electron microscopy and x-ray photoelectron spectroscopy, the surface of the polydopamine-coated and noncoated seeds was characterized. The detachment stress between the two types of seeds and the tissue was measured. The efficacy of polydopamine-coated seed was investigated through in vitro migration tests by tracing the seed location after tissue implantation and shaking for given times. The cytotoxicity of the polydopamine coating was also evaluated. The results of the coating characterization have shown that polydopamine was successfully coated on the surface of the seeds. In the adhesion test, the polydopamine-coated seeds had 2.1-fold greater detachment stress than noncoated seeds. From the in vitro test, it was determined that the polydopamine-coated seed migrated shorter distances than the noncoated seed. This difference was increased with a greater length of time after implantation. The authors suggest that polydopamine coating is an effective technique to prevent migration of implanted seeds, especially for permanent prostate brachytherapy.

Using decomposed Nafion ionomers to anchor Pt nanoparticles and improve their durability during methanol electro-oxidation

Nafion ionomers were partially decomposed to produce oxygenated functional groups on Vulcan XC72R (XC72R) that enabled increased Pt ion adsorption when the functionalized XC72R was immersed in a 5 mM aqueous H2PtCl6 solution. X-ray absorption spectroscopy spectra indicated that the oxidation state for the Pt ions remained unchanged upon adsorption on the functionalized XC72R whereas a notable reduction in the oxidation state was recorded when the Pt ions were adsorbed onto untreated XC72R. After a hydrogen reduction treatment, the Pt nanoparticles on the functionalized XC72R demonstrated impressive mass activities and durability retention during the methanol electro-oxidation reaction (MOR), compared to those of commercial E-TEK Pt/C samples. After the durability test, transmission electron microscope images showed that the Pt nanoparticles on the functionalized XC72R exhibited significantly reduced agglomeration, and X-ray photoelectron spectra confirmed that the functional groups from the decomposed Nafion ionomers were still present. We attributed the notable durability improvement to the anchoring effect of decomposed Nafion ionomers that prevented the Pt nanoparticles from contacting XC72R directly, thus minimizing the undesirable migration and detachment of Pt nanoparticles during repeated MOR cycles.

Coupled NOx storage and reduction and selective catalytic reduction using dual-layer monolithic catalysts

Lean reduction of NOx (NO and NO2) was studied using monolith-supported catalysts consisting of a layer of a metal-exchanged (Fe, Cu) zeolite (ZSM-5) selective catalytic reduction (SCR) catalyst deposited on top of a Pt/Rh/BaO/CeO2 lean NOx trap (LNT) catalyst. During periodic switching between lean and rich feeds, the LNT layer reduces NOx to N2 and NH3. The SCR layer traps the latter, resulting in additional NOx reduction. The dual-layer catalysts exhibited high N2 selectivity and low NH3 selectivity over the temperature range of 150–300°C. The NOx conversion was incomplete due to undesired side reactions in the LNT layer, such as NH3 oxidation to N2O at low temperature and NOx at high temperature. The NOx conversion and N2 selectivity of the Cu-exchanged ZSM-5 was higher than that of the Fe-exchanged ZSM-5. This was due to a higher low temperature SCR activity and a higher NH3 storage capacity on the Cu-zeolite. The dual-layer catalyst had a higher NOx conversion than the LNT catalyst below 300°C and a higher N2 selectivity over the entire temperature range when H2O and CO2 were present in the feed. The NOx storage capacity and NH3 generation increased upon addition of CeO2 to the LNT layer below 250°C. It also led to increased NH3 oxidation at high temperatures. The addition of ceria mitigated the undesirable migration of Pt between the LNT and SCR layers. Hydrothermal aging had a smaller effect on dual-layer catalysts containing ceria.