Exchange Character Research Articles

Chiral zwitterionic stationary phases based on Cinchona alkaloids and dipeptides – design, synthesis and application in chiral separation

Chiral resolution of polar organic compounds such as amino acids and peptides represents an important chromatographic task due to increasing significance of natural species, which play important signaling and regulatory roles in the living organisms. Despite the number of available chiral stationary phases, this task remains challenging, since not many of the commercially available systems are capable to resolve non-derivatized zwitterionic species. In this study, we present a target-oriented design of a new class of chiral selectors. Pursuing the goal to separate amino acids, and especially short peptides, we have combined Cinchona alkaloids – quinine and quinidine – with three different biogenic dipeptides. We have synthesized six different chiral stationary phases, with selector loading of ∼200 μmol g−1, and tested their chiral recognition capabilities for acidic, basic and zwitterionic analytes using various mobile phases. We have observed that all chiral stationary phases retain the chiral anion exchange capability known for commercially available Cinchona-based columns leading to baseline or partial resolution of six out of ten analytes. The performance in chiral resolution of basic analytes is not optimum due to the weak cation exchange character of the peptidic residue. However, we report on encouraging results in the chiral resolution of short peptides, for which, depending on their structure, we see the chiral resolution of up to three stereoisomers (from four possible) in a preliminary screening.

Stretchable conductive hydrogel with super resistance-strain stability and ultrahigh durability enabled by specificity crosslinking strategy for high-performance flexible electronics

Stretchable ionic conductive hydrogels (SICHs) are regarded as one of the indispensable components for flexible electronics desirable to provide stable signal transmission and functional reproducibility. However, the state-of-the-art SICHs demonstrate a narrow resistance-stability range and poor cyclical fatigue reliability due to ion migration limitations and the absence of the molecular design regime. Herein, we present a novel synthetic strategy that utilizes the dynamic Zn-carboxyl physical bonding, adjacent to B-hydroxyl chemical bonding, to realize the “specificity” cross-linking in pectin polymeric networks. This approach significantly extends the resistance-stability range of SICHs, while also providing remarkable longevity. Via “specificity” crosslinking design, the Zn-carboxyl physical bonding, bearing thermodynamically stable and dynamic exchange character, can break the resistance-strain dependence of ionic conductive hydrogel, offering an unprecedented resistance-stability under largely applied strain (300%). Moreover, the B-hydroxyl chemical bonding effectively overcomes the conductivity and mechanical strength trade-off dilemma due to its strong but dynamic feature, realizing the high durability of SICHs. In addition, the extraordinary tolerate harsh environment capacity was achieved by introducing glycerin to form rich hydrogen bonds in the SICHs network, which is crucial for the avoidance of congelation at subzero temperatures and dehydration resulting from the circuit heat. As a stretchable conductive component of deformable electronic devices, the SICH demonstrates extraordinary long life and stable operation. These observations reveal fresh stretchable conductive materials.

Micellar and sub-micellar chromatography with a cocamidopropyl betaine surfactant

We have coated a typical C18 column with the pH cationic charge controllable zwitterionic synthetic surfactant, cocamidopropyl betaine (CAPB), in order to generate a mixed mode reversed phase weak ion exchange column. As determined by the Thomas model, the column has an adsorbed surfactant capacity of 0.557 mmoles. The addition of 8.8 × 10–4 M CAPB to the totally aqueous mobile phase ensured stability of the surfactant on the column and permitted separation of the four component sulfonamide mixture with micellar liquid chromatography (MLC) in under 11 min. Comparatively, with a dilute H2SO4 mobile phase with no CAPB, the separation time for the sulfonamide mixture reached an excessive run time of an hour on the bare C18 chains. With CAPB in the mobile phase (no organic solvent present), a seven component sulfonamide mixture could be separated in less than 45 min. A five component short chain carboxylic acid mixture, separated in 20 min, was used to examine the ion exchange character of the column in pH environments of 2.3 and 4.6. Three phase MLC equilibrium analysis was also done in these pH environments with the sulfa drug and carboxylic acid mixtures to determine partition coefficients. Finally, a quite high molecular weight (70,000) anionic polystyrene sulfonate polymer was characterized by MLC with only CAPB and variable pH mobile phases; the optimal pH was determined to be 5.6. A totally aqueous mobile phase without CAPB was not suitable for profiling this polymer.

Experimental research on condensation heat transfer characteristics of low mass flow rate steam in a horizontal tube

The heat exchange character of pure steam flow inside horizontal vacuum tubes has been experimentally studied. The inside diameter and length of the tube are 38 mm and 3400 mm, respectively. The effects of steam mass flow rate, saturated temperature, and total temperature difference ΔTs,c on the flow process are analyzed. Based on the analysis of the heat exchange mechanism of stratified flow condensation, a calculation model of the thermal partition angle is established. The experimental results show that the thermal partition angle increases with the increase of the mass flow rate, and the rise of the heat transfer temperature difference. The saturated temperature has little impact on the local heat transfer coefficient and the thermal partition angle of condensation in the tube. By taking the thermal partition angle as the partition boundary, an empirical correlation formula for calculating the local heat transfer coefficients is established to better predict the results of local heat transfer coefficients.

Modified Poly(vinylidene fluoride) by Diethylenetriamine as a Supported Anion Exchange Membrane for Lithium Salt Concentration by Hybrid Capacitive Deionization.

This paper shows the investigation for the optimal anion exchange membranes (AEM) supporting the desorption step of the HCDI process. The chemical modification of PVDF by diethylene triamine created the AEM. To confirm the ion-exchange character of materials, the chemical analysis with FTIR, SEM, surface energetics, and transportation analysis were applied. Next, the investigated membranes were applied for the sorption and desorption of lithium chloride. The specific sorptive parameters were higher according to the incorporation of the nitrogen groups into polymeric chains. Considering the desorption efficiency, membranes modified by four days were selected for further evaluation. The application in the HCDI process allowed reaching the desorption efficiency at 90%. The system composed of PVDF-DETA4 membrane was suitable for sorption 30 mg/g of salt. By applying the PVDF-DETA4 membrane, it is possible to concentrate LiCl with four factors. The anion exchange character of the developed membrane was confirmed by adsorption kinetics and isotherms of chlorides, nitrates, sodium, and lithium. The prepared membrane could be considered a perspective material suitable for concentration salt with electro-driven technologies for the above reasons.

Heat exchange character and thermal comfort of young people in the building with solar radiation in winter

Indoor solar radiation notably affects the thermal environment and the character of human heat exchange with the ambient environment. Based on the field experiments of human body thermal comfort under indoor solar radiation in winter, this paper analyzes heat exchanges between the human body and the surrounding environment and the local and overall skin temperature, and discusses the relationship between heat exchange and thermal sensation. The results show that the skin temperature of the left upper arm and left thigh under radiation is 3.3 °C and 2.0 °C higher than that without radiation. As the irradiated area increases, convection and evaporation heat loss increase, and total heat loss decreases. When the thermal sensation of the human body is in a neutral state, the proportions of heat loss by convection, radiation and evaporation are 33.9%, 47.1% and 10.4%, respectively.

Several Physiological Changes of Cocoa (Theobroma cacao L.) in Response to Vascular Streak Dieback Diseases

The physiological response of cocoa plants under VSD infections is still limited because there is no method in artificial inoculation since Oncobasidium theobromae was reported as parasitic obligates. The investigation of correlation between cocoa responses and VSD attack becomes important information to figure out the effect of decreased productivity as the consequences of the physiological damages. The objective of this research was to describe the pathogen infection and the symptom of VSD through fungal staining method and to asses the changes of some physiological aspects (chlorophyll and gass exchange character) under VSD pathogen infection. This study was conducted in Kaliwining experimental station, ICCRI, Jember, East Java, Indonesia. The result of the study indicated that late infection stage caused chlorophyll degradation, decreasing transpiration rate, and increasing temperature in both tolerant clone (Scavina 6) and susceptible clone (TSH 858). The rate of photosynthesis, stomatal conductance, and concentration of CO 2 in susceptible clone (TSH 858) showed a drastic decrease when infected by VSD pathogen than that of in healthy plants. In resistant clone (Scavina 6), photosynthesis rate, stomatal conductance, and concentration of CO 2 showed no significant decrease when infected by VSD pathogen compared to that non-infected condition.

Novel anion exchange membrane for concentration of lithium salt in hybrid capacitive deionization

Novel anion exchange membranes that blocks the co-ions effect and improve the desorption step in hybrid capacitive deionization (HCDI) process have been presented. The membranes were prepared by chemical modification of poly(vinylidene fluoride) by ethylene diamine. To confirm ion exchange character and electrical properties of obtained membranes such methods as FTIR, SEM and EIS were applied. Transport phenomenon was described by Arrhenius and Eyring-Polanyi equations. On their bases, taking into account desorption efficiency, membrane modified for 24 h was selected for the further investigation. Its application to the HCDI system allowed to obtain desorption efficiency at 96% level with over 0.9 current efficiency. The salt adsorption capacity of the system reached over 30 mg per 1 g of electrode. For these reasons the evaluated membrane could be considered as perspective material for salt concentration with electro driven process.

Optimal power series expansions of the Kohn\u2013Sham potential

A fundamental weakness of density functional theory (DFT) is the difficulty in making systematic improvements to approximations for the exchange and correlation functionals. In this paper, we follow a wave-function-based approach [N.I. Gidopoulos, Phys. Rev. A 83, 040502 (2011)] to develop perturbative expansions of the Kohn–Sham (KS) potential. Our method is not impeded by the problem of variational collapse of the second-order correlation energy functional. Arguing physically that a small magnitude of the correlation energy implies weak perturbation and hence fast convergence of the perturbative expansion for the interacting state and for the KS potential, we discuss several choices for the zeroth-order Hamiltonian in such expansions. Our first two choices yield KS potentials containing only Hartree and exchange terms: the exchange-only optimized effective potential (xOEP), also known as the exact-exchange potential (EXX), and the Local Fock exchange (LFX) potential. Finally, we choose the zeroth order Hamiltonian that corresponds to minimum magnitude of the second order correlation energy, aiming to obtain at first order the most accurate approximation for the KS potential with Hartree, exchange and correlation character.

Economic analysis of exporting Serbian honey

Researching competitiveness of Serbia’s honey sector represents an introduction into a complex issue of dynamic changes with complex heterogenic and long term socio-economic implications. Tracking changes of comparative advantages in export during Serbia’s transition period and accession to the EU is significant for viewing the effects that trade liberalization and integration in international streams have on the sensitive honey sector. The research started from indicators of demand and level of foreign trade in the EU. Quantitative indicators of Serbia’s honey export on European market were shown in order to confirm Serbia’s potential and dominant presence. Research subject of this paper is the analysis of Serbia’s comparative advantage in exporting honey and specialization in international trade with the EU. The Balassa index, Revealed comparative advantages index and Revealed symmetric comparative advantage index were used with the goal to measure the level of Serbia’s comparative advantage, Grubel Lloyd Index and Trade Balance Index were used to measure the specialization level. Research results point to a positive comparative advantage value in exporting Serbia’s honey to EU and inter-industry exchange character.

A Survey of the 14C Content of Dissolved Inorganic Carbon in Chinese Lakes

AbstractWe present radiocarbon (14C) measurements of dissolved inorganic carbon (DIC) from surface waters of 11 lakes, widely distributed in China. Surface lake water DIC F14C values show distinct differences, and we relate these to the physical exchange character (“open” or “closed”) of each lake. Open lakes studied here generally have lower DIC F14C values than closed lakes. We present a simple model of a lake water cycle to calculate an average residence time for each lake. Comparisons between lake DIC F14C and average residence time shows that the DIC F14C increases with the average residence time and reflects a steady-state.

Switching of the exchange interaction character in the binuclear copper(II) complexes based on the hetaryl derivatives of 1,3-diaminopropanol-2

The binuclear copper(II) complex with bis-azomethine, viz., the product of condensation of 1,3-diaminopropanol-2 with 4-hydroxy-3-formylcoumarin (H3L), of the composition [Cu2L(μ2-CH3COO)] (I) is synthesized and studied. Complex I is characterized by the exchange interaction of the antiferromagnetic type (2J =–112 cm–1), which is switched to the ferromagnetic one (2J = +106 cm–1) after the recrystallization of the complex from dimethyl sulfoxide (DMSO) to form solvate [Cu2L(μ2-CH3COO)(μ2-DMSO)] · 0.5DMSO (II). The structure of solvate II is studied by X-ray diffraction analysis (CIF file CCDC no. 982198). The difference in the exchange character is explained by the stabilization by the μ2-coordinated DMSO molecule of a distorted (roof-shaped type) conformation of the polydentate ligand and the complex as a whole, unlike the symmetric conformation characteristic of the nonsolvated complex. The data obtained are compared with those on similar compounds synthesized earlier and with the quantum chemical modeling results for the exchange interaction in the framework of the DFT-BS approximation.

Crisis phenomena in Central Asian direction development of Russian foreign trade in the Orenburg direction in the 1st quarter of the 19th century

The paper contains analysis of development tendencies of the Russian Empire foreign trade with Central Asian khanates in the first quarter of the 19th century. The authors found that the Russian State didnt pay much attention to the Asian customs policy in this direction for a long time. It was due to the fact that the trade with Central Asian khanates was of exchange and caravan character. The author came to the conclusion that the heads of the Orenburg Region - military and civil governors - made great efforts to change that situation and made special rules for the foreign trade development in the Orenburg Region. It promoted commodity turnover increase. The author proved that in the first quarter of the 19th century the most important element of Central Asian trade development crisis in the Orenburg direction was the fact that merchants from Central Asia dominated Russian merchants in the numerical ratio. However, the ministry of finance and E.F. Kankrin refused to forbid Central Asian merchants to trade at internal Russian fairs as it would result in stagnation in trade and would make prices for goods higher. This problem for the first quarter of the 19th century couldnt be solved as it was connected with the geopolitical status quo existing in the region. It only started to get solutions with an active military advance of Russia to Central Asia in the second half of the 19th century.

Binuclear copper(II) complexes based on acyldihydrazones of imino-, oxo-, and thiodiacetic acids and 2-hydroxyacetophenone

The results of studying the binuclear copper(II) complexes with acyldihydrazones of amino-, oxo-, and thiodiacetic acids and 2-hydroxyacetophenone were described. The temperature variations of the EPR spectra of solutions with a seven-line hyperfine structure indicating an exchange character of interaction between unpaired electrons and the two equivalent nuclei of copper atoms were studied.

Stabilization of Candida antarctica Lipase B (CALB) Immobilized on Octyl Agarose by Treatment with Polyethyleneimine (PEI)

Lipase B from Candida antarctica (CALB) was immobilized on octyl agarose (OC) and physically modified with polyethyleneimine (PEI) in order to confer a strong ion exchange character to the enzyme and thus enable the immobilization of other enzymes on its surface. The enzyme activity was fully maintained during the coating and the thermal stability was marginally improved. The enzyme release from the support by incubation in the non-ionic detergent Triton X-100 was more difficult after the PEI-coating, suggesting that some intermolecular physical crosslinking had occurred, making this desorption more difficult. Thermal stability was marginally improved, but the stability of the OCCALB-PEI was significantly better than that of OCCALB during inactivation in mixtures of aqueous buffer and organic cosolvents. SDS-PAGE analysis of the inactivated biocatalyst showed the OCCALB released some enzyme to the medium during inactivation, and this was partially prevented by coating with PEI. This effect was obtained without preventing the possibility of reuse of the support by incubation in 2% ionic detergents. That way, this modified CALB not only has a strong anion exchange nature, while maintaining the activity, but it also shows improved stability under diverse reaction conditions without affecting the reversibility of the immobilization.

Polymer Electrolyte Membrane Fuel Cell Performance of a Sulfonated Poly(Arylene Ether Benzimidazole) Copolymer Membrane

Disodium-3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (SDCDPS) and 5,5′-bis[2-(4-hydroxyphenyl)benzimidazole] (HPBI) monomers were synthesized. Binding these monomers via nucleophilic aromatic polycondensation reaction, a sulfonated poly(arylene ether benzimidazole) copolymer was synthesized. Structures of monomers and copolymer were confirmed by proton nuclear magnetic resonance spectroscopy (1H NMR) and Fourier transform infrared (FTIR) spectroscopy analyses. Proton exchange membrane was prepared by dissolving copolymer in dimethylacetamide (DMAc) and casting onto a glass plate. Copolymer membrane was doped with sulfuric acid to ensure proton exchange character. Single cell performance of the copolymer membrane was tested in a polymer electrolyte membrane fuel cell test station. The highest power density of the membrane was measured as 23.7 mW cm−2 at 80°C. Thermogravimetric analysis (TGA) showed that as the degree of disulfonation is increased thermal stability of the copolymer is increased.

Preparation of a weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography stationary phase for protein separation using click chemistry.

In this study, 3-diethylamino-1-propyne was covalently bonded to the azide-silica by a click reaction to obtain a novel dual-function mixed-mode chromatography stationary phase for protein separation with a ligand containing tertiary amine and two ethyl groups capable of electrostatic and hydrophobic interaction functionalities, which can display hydrophobic interaction chromatography character in a high-salt-concentration mobile phase and weak anion exchange character in a low-salt-concentration mobile phase employed for protein separation. As a result, it can be employed to separate proteins with weak anion exchange and hydrophobic interaction modes, respectively. The resolution and selectivity of the stationary phase were evaluated in both hydrophobic interaction and ion exchange modes with standard proteins, respectively, which can be comparable to that of conventional weak anion exchange and hydrophobic interaction chromatography columns. Therefore, the synthesized weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography column can be used to replace two corresponding conventional weak anion exchange and hydrophobic interaction chromatography columns to separate proteins. Based on this mixed-mode chromatography stationary phase, a new off-line two-dimensional liquid chromatography technology using only a single dual-function mixed-mode chromatography column was developed. Nine kinds of tested proteins can be separated completely using the developed method within 2.0 h.

A bifunctional adsorbent with high surface area and cation exchange property for synergistic removal of tetracycline and Cu2+

Abstract A novel bifunctional adsorbent with high surface area and cation exchange character (HAR-2) was prepared via copolymerization and hydrolysis reactions for the coremoval of tetracycline and Cu 2+ . HAR-2 possessed large specific surface area of 394 m 2 /g and high weak cation exchange capacity of 1.06 meq/g. The adsorption kinetics of TC or Cu 2+ fitted both pseudo-first-order and pseudo-second order equations in single-substrate solution, whereas the adsorption kinetics were better described by pseudo-second order model in binary solutions. The adsorption of TC was an exothermic process, while the Cu 2+ adsorption process was endothermic. The adsorption isotherms of TC and Cu 2+ fitted the Langmuir model, suggesting a monolayer adsorption process. The adsorbed amount of TC was pronouncedly enhanced in the presence of Cu 2+ due to the formation of tertiary surface complex HAR–Cu 2+ –TC. Likewise, the adsorption of Cu 2+ was significantly improved by forming HAR–TC–Cu 2+ complex in the presence of TC. The uptake of Cu 2+ increased as pH increased, while the adsorbed amount of TC increased as pH rose from 2 to 3 but decreased when pH was further elevated from 3 to 6. The presence of NaCl exerted no significant influence on the adsorption of TC and negatively affected the adsorption of Cu 2+ . HAR-2 exhibited high stability over 5 repeated uses, only losing 6.3% and 18.4% of the initial adsorption capacity for TC and Cu 2+ , respectively.

업무시설의 문화.복지공간 특성이 업무태도에 미치는 영향관계 분석 - NHN GreenFactory 복지제도와의 비교적 관점에서 -

The spatial planning of a office building is shifting from cellular type office to the form of emphasis on culture, welfare, and communication. As the trend, this study analyzes work attitudes which are influenced by welfare=cultural space and welfare system. The causative factors derived from the improved work space are flexibility and independency of work exclusive space. The work support space is consisted of cultural exchange and welfare convenient character. In comparison to work space, the causative factors derived from welfare system are self-development, support payment, and life support. The resultant factors of the study includes accountability, sincerity, trustworthiness, cooperativity, and creativity. The study results showed that improved work exclusive space, work support space, and welfare system had a positive impact at a similar level on work attitudes formation. In the case of work exclusive space, flexibility was only found to have a positive influence on sincerity, and independency has a positive influence on trustworthiness and cooperativity. However, in the case of work support space, cultural exchange was found to have a positive influence on accountability, sincerity, trustworthiness, and cooperativity, and welfare convenient has a positive influence on creativity. And so, support payment has a positive influence on trustworthiness and creativity. These results means that improvement of space for communication and economic support system to stablize their life are major factors in the formation of positive attitudes.

Study of the interaction in the ZnS (ZnO)-Dy2S3 system

The exchange reactions of the impurity ZnO in zinc sulfide produced by self-propagating high-temperature synthesis with the additive Dy2S3 were studied by IR spectroscopy and diffuse reflectance electron spectroscopy. It was found that the main products of the interaction in the ZnS (ZnO)-Dy2S3 system are ZnS and Dy2O2S. The exchange character of the interaction was modeled by the systems ZnO-Dy2S3 (2: 1) and Dy2S3-Dy2O3 (1: 2). The possibility of estimating the ZnO impurity content of zinc sulfide was demonstrated, which allows one to optimize the zinc sulfide synthesis conditions.