Exchange Step Research Articles

Functional metallic circuitries created by laser-activated selective electroless plating for 3D customized electronics

Laser-activated selective electroless plating (LASELP) is a promising complementary manufacturing process employed in hybrid additive manufacturing (HAM) technology for the fabrication of customized 3D electronics. However, to the best knowledge of the authors, most current LASELP technologies could only enable copper deposition on/within the polymer matrix, which largely limited the application scope of this technology. Accordingly, an advanced LASELP technology combining catalyst exchanging process is proposed to pattern diverse functional metal on the photopolymer to fabricate 3D electronics. Two kinds of catalyst systems are selected in this HAM technology: (1) Cu2(OH)PO4; (2) antimony tin oxide (ATO) and titania (TiO2). Silver and nickel-phosphorus (Ni-P) alloy were selected as the representatives of direct- and indirect-ELP metals. Silver could directly plated on the laser-activated surface to deposit a dense and highly conductive layer, while for the Ni-P layer, an inevitable catalyst exchange step was applied here to induce Pd0 plating seeds on the laser-activated substrate. Finally, a variety of customized electronics, such as conformal circuit boards, smart structure with strain sensor, embedded structural thermometer, Internet of Things bottle cap, and gas tube integrated with 3D conformal NO2 sensor were implemented are fabricated and fully verify this HAM technology.

A proposal in STEM for virtual exchange held by Computer Science and Applied and Computational Mathematics programs

In this practice report, we present a practical experience of a virtual exchange carried out by a Belgian and a Brazilian professor from two research intensive universities in Northwestern Europe and in Latin America, respectively. Particularly, this paper is focused on how we designed a common syllabus in a specific topic of STEM, aiming to explore math and computer science skills of the students, and how we implemented this virtual exchange step by step, despite the students being from different courses and different levels of degree. In addition, we discuss the pros and cons of the process from the instructors’ perspective as well as under students’ views, and provide some suggestions to be applied and tested for future virtual exchanges in this field. Overall, this practice report reinforces our deep reflection about the results and desire to share our STEM syllabus to encourage other colleagues to apply it (or modify it) for different courses.

16O2 – 18O2 interface exchange study between gas phase and the BaFeO3–δ oxide

Studies of oxygen surface exchange kinetics for BaFeO3–δ oxide were performed using the oxygen isotope exchange method with pulsed supply of an isotopically enriched mixture (PIE) at the partial oxygen pressure 21.3 kPa in the temperature range of 350–600 °С. Oxygen surface exchange kinetics was considered in the framework of two-step model including two consecutive steps: dissociative adsorption of oxygen and incorporation of oxygen adatoms into the crystal lattice of the oxide. The rates of oxygen heterogeneous exchange (rH), as well as the rates of dissociative adsorption (ra) and oxygen incorporation (ri), have been calculated. The process of oxygen dissociative adsorption at the surface of BaFeO3–δ oxide was found to be the rate-determining step of the surface exchange. The appropriate models describing the oxygen exchange kinetics and possible mechanisms occurring in the system “gaseous oxygen – BaFeO3–δ oxide” were discussed.

Towards More Sustainable Schiff Base Carboxylate Anodes for Sodium-Ion Batteries.

Bismine sodium salt (BSNa), a Schiff base with two sodium carboxylates, has shown promising electrochemical performance as an anode material. However, its synthesis involves toxic reagents and generates impurities, requiring significant solvent use for purification. This study introduces a novel synthetic method using sodium hydroxide as the sole reagent, which acts as both a base and Na source in the ion exchange step. With this procedure, we reduce the amounts of chemicals, diminish toxicity, improve the purity of the target compound, and use less solvent while maintaining comparable electrochemical performance. Additionally, the procedure is carried out under anhydrous conditions that avoid the undesirable hydrolysis of the imine linkages. In a previous report, the processing of the composite electrode was not established. In this article, we address this issue; the electrochemical performance, specifically the rate capability, is enhanced by processing the electrodes in laminate form rather than powder. As alternative to N-methyl-2-pyrrolidone (NMP), a common but disadvantageous solvent in laminate processing, other solvents were explored by testing acetone (DMK), methylisopropylketone (MIPK), and a DMK-NMP mixture. The remarkable electrochemical performance (specific capacity of 260-280 mAh/g, and capacity retentions higher than 84% at 1C (260 mA/g) remained consistent across these solvents. Furthermore, we investigated replacing copper with aluminum as the current collector to reduce costs and increase the energy density of the battery. While aluminum performed comparably to copper at low specific currents C/10 (26 mA/g), it showed a significant shift in the redox process potentials at higher specific currents.

Sintering of different silica aerogels

This work reports on isothermal sintering experiments, conducted with silica aerogel samples in a broad density range (∼0.025–0.277 kg/m3) made by the same process by varying the solvent-to-sol ratio, as well as samples made by different formulations used by several aerogel manufacturers. The latter comparison is deficient in the literature. Low-density (<0.05 kg/m3) aerogels were found to be significantly more resilient to sintering, which is consistent with established sintering theories. Unexpectedly large variability in the susceptibility to sintering was observed in similar density (∼0.1 kg/m3) aerogels made by different formulations and by different producers. All material made by utilizing a CO2 solvent exchange step prior to supercritical drying exhibited effects attributable to residual original solvent in the micropores. This alludes to an incomplete solvent exchange process. The materials were examined in the context of devising a methodology for producing an ultra-pure silica aerogel, a substance free of organic constituents, intended to serve NASA life detection mission needs.

The Wood-rot Basidiomycete Candolleomyces eurysporus VAST02.52 Produces a Versatile Peroxidase that Catalyses the Biotransformation of α-Pinene to Release Verbenone

Background Versatile peroxidase (VP; EC 1.11.1.16) has recently emerged as a novel peroxidase highly valued in biotechnology due to its exceptional ability to oxidize a diverse range of substrates into value-added products. Objectives To gain insight into the versatile peroxidase system from fungi, this study was designed to purify and characterize a CeuVP from the newly isolated fungus Candolleomyces eurysporus and to investigate its involvement in the biotransformation of plant α-pinene. Materials and methods The fungal isolate was identified by analysis of the internal transcribed spacer region. VP-active protein was purified from liquid culture of C. eurysporus VAST02.52 by using fast protein liquid chromatography. The catalytic properties and stability of enzyme were studied for various substrates, different pH- and temperatures. Moreover, its involvement in the biotransformation of plant α-pinene was assessed by HPLC chromatography. Results CeuVP was successfully purified with 27.3-fold purity and a 20.9% yield by using three steps of anion exchange and size exclusion chromatography. The molecular weight of CeuVP was determined to be 40 kDa by SDS-PAGE electrophoresis. This pure enzyme exhibited optimal activity at pH 4.0 and 35 °C. CeuVP showed the highest specific activity of 231.6 U/mg against ABTS, followed by Mn2+ (205.8 U/mg), veratryl alcohol (112.7 U/mg), cathecol (77.8 U/mg), p-aminophenol (68.9 U/mg), RBBR (56.2 U/mg), 4-methoxyphenol (31.1 U/mg), guaiacol (18.3 U/mg), and Reactive Black 5 (12.9 U/mg). Moreover, CeuVP catalyzed the oxidation of α-pinene derived from the essential oil of Eucalyptus robusta to release verbenone as the sole metabolite after a 7 h incubation. Conclusions Versatile peroxidase ( CeuVP) from C. eurysporus VAST02.52 exhibits the highest specific activity against ABTS while also catalyzing oxidation of various substrates tested. Moreover, this study indicated that CeuVP could be effective in the bioconversion of α-pinene into verbenone, a promising compound with numerous applications in the flavors and fragrances industry.

Improved one-pot protein synthesis enabled by a more precise assessment of peptide arylthioester reactivity

By investigating 17 peptide arylthioesters that were previously challenging to produce, this study reveals a clear correlation between increased ligation activity and decreased pKa values of their corresponding arylthiols. The observed differences are attributed to variations in thioester bond strength and steric hindrance. These insights have led to the development of an improved one-pot chemical protein synthesis approach that leverages the reactivity differences between peptide arylthioesters with C-terminal Ala-S-Ph(4-NO2) and Ala-S-Ph(2,6-diCH3). This approach eliminates the need for thiol-thioester exchange and additive removal steps while enabling in situ desulfurization, thereby significantly simplifying the protein synthesis process.

An unconventional strategy for purifying recombinant SARS-CoV-2 spike protein

The soluble domain of the trimeric SARS-CoV-2 spike protein is a promising candidate for a COVID-19 vaccine. Purification of this protein from mammalian cell culture supernatant using conventional resin-based chromatography is challenging as its large size (∼550 kDa) restricts its access and mobility within the pores of the resin particles. This reduces binding capacity and process robustness very significantly as extremely low flow rates need to be used during purification. Convection-based ion-exchange membrane chromatography has been found to be suitable in this respect. However, the high ionic strength of mammalian cell culture supernatant makes it difficult to bind this protein on charged membranes without dilution with a suitable buffer. An unconventional strategy involving size-exclusion chromatography as the first step, followed by cation exchange membrane chromatography as the second step is proposed in this paper. In the size exclusion chromatography step, the spike protein is excluded from the pores and can therefore be isolated in the void volume fraction. This step removes small molecule impurities and also serves as a desalting and buffer exchange step, making the partially purified material suitable for the cation exchange membrane chromatography step. The proposed process is variant-independent, fast and scalable and addresses some of the challenges associated with the currently used purification methods.

Effect of doping with iron and cations deficiency in the high conductive electrolyte La0.8Sr0.2Ga0.8Mg0.2O3–δ on oxygen exchange kinetics

The oxygen isotope exchange method was used to investigate the kinetics of the interaction between gaseous oxygen and LaGaO3-based oxides in a temperature range of 650 to 850 °C, with an oxygen pressure of 10 mbar. The stable isotopes of 18O/16O were used as labelled ions. The temperature dependencies of the heterogeneous oxygen exchange rate (rH), the oxygen dissociative adsorption rate (ra), the oxygen incorporation rate (ri), and the oxygen diffusion coefficient (D) were determined. A comparative analysis of the rH and D values for La0.8Sr0.2Ga0.8Mg0.2O3–δ was carried out with a view to identifying any similarities or differences when compared with the literature data on oxides with similar compositions. The effect of FeGa′ doping and the creation of an A-sublattice deficiency on the kinetic characteristics were investigated using the (La0.8Sr0.2)0.98Ga0.7Fe0.1Mg0.2O3–δ oxide as a case example. Correlations between the rate-determining step of oxygen exchange and the modification of the oxide composition were identified.

Preparation of 2-Aminoimidazole-Activated Substrates for the Study of Nonenzymatic Genome Replication.

Nonenzymatic genome replication is thought to be an important process for primitive lifeforms, but this has yet to be demonstrated experimentally. Recent studies on the nonenzymatic primer extension mechanism mediated by nucleoside 5'-monophosphates (NMPs) activated with 2-aminoimidazole have revealed that imidazolium-bridged dinucleotide intermediates (N*N) account for the majority of the chemical copying process. As a result, an efficacious synthetic pathway for producing substrates activated with an imidazoyl moiety is desirable. This article provides a detailed protocol for the standard dehydrative redox reaction between NMPs and 2-aminoimidazole to produce nucleotide phosphoroimidazolides. In addition, we describe a similar synthetic pathway to produce N*N in high yields for homodimers. Finally, a simple reversed-phase cation exchange step is described to increase NMP solubility, which significantly increases yields for certain substrates. This approach allows for an efficient and cost-effective methodology to prepare high-quality substrates utilized in origins-of-life studies. © 2024 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Synthesis of 2-aminoimidazolephosphoroimidazolide-activated cytidine Basic Protocol 2: Synthesis of 2-aminoimidazolium-bridged dicytidyl intermediate Basic Protocol 3: Cation exchange of guanosine 5'-monophosphate disodium salt Alternate Protocol: Synthesis of cytidine 5'-phosphoroimidazolide or 2-aminoimidazolium-bridged dicytidyl from cytidine 5'-monophosphate disodium salt.

Nanoparticle concentration and solvent exchange via organic solvent ultrafiltration

Downstream processing of nanoparticles after synthesis frequently involves purification, concentration and solvent exchange steps. While these are typically done via centrifugation in lab scale, ultrafiltration is a practical and economical alternative in large scale continuous production. Treating suspensions in organic solvents via ultrafiltration requires solvent-stable membranes and in this study we present the performance of cellulose ultrafiltration membranes in the concentration and solvent exchange of hydrophilic and hydrophobized silica nanoparticles using isopropanol, water, dimethyl formamide and ethanol as solvents. Hydrophobized particles formed less permeable cake layers than hydrophilic particles during concentration. All fouling was reversible upon ultrasonication while physical cleaning via stirring could only recover the complete membrane permeance fouled with hydrophilic particles in dimethyl formamide and hydrophobic particles in isopropanol and water. Quality of nanoparticle recovery was assessed by the amount recovered in retentate and cleaning suspensions as well as the particle size after these steps. Highest recovery of hydrophilic particles was obtained in dimethyl formamide and that of hydrophobic particles in isopropanol. No agglomeration of recovered hydrophilic particles was observed, while hydrophobic particles recovered via physical cleaning partly agglomerated in isopropanol and dimethyl formamide. Finally, continuous solvent exchange from isopropanol to ethanol, water and dimethyl formamide was achieved with no performance loss throughout the process.

Unlocking the electrochemical potential of carbon aerogels: Tailored performance via controlled carbonization and activation process

In this study, Carbon Aerogels (CAs) were prepared by high-temperature supercritical drying (HTSD) in ethanol for supercapacitors (SCs). HTSD eliminates the acetone-liquid CO2 exchange step and offers a time-efficient alternative to traditional liquid CO2 drying methods. This study investigated the effect of varying carbonization temperatures (600, 700, 800, and 900 °C) on resorcinol-formaldehyde aerogel and assessed their impact on structural, morphological, compositional, and surface area properties. Amongst, CA carbonized at 700 °C (CA-7) exhibited superior performance with a specific capacitance (Cs) of 78 F/g, energy density (Ed) of 39 Wh/kg at 2 A/g in 1 M Na2SO4. After KOH activation, CA-7 demonstrated two-fold enhancement in Cs (184 F/g at 2 A/g) and three-fold in Ed (93 Wh/kg) while maintaining 98 % capacitance retention over 7000 cycles. The symmetric aqueous device (ACA\\SSM||ACA\\SSM) exhibited a Cs of 32 F/g, Ed of 25 Wh/kg, Pd of 2308 W/kg, and 88.6 % retention over 2500 cycles at 2.4 V. This research highlights the advantages of HTSD-based CA synthesis and the potential of activated CA and Na2SO4 to achieve high Ed for SCs.

Tailoring polishing steps for effective removal of polysorbate-degrading host cell proteins in antibody purification.

Ensuring the quality and safety of biopharmaceutical products requires the effective separation of monoclonal antibodies (mAbs) from host cell proteins (HCPs). A major challenge in this field is the enzymatic hydrolysis of polysorbates (PS) in drug products. This study addresses this issue by investigating the removal of polysorbate-degrading HCPs during the polishing steps of downstream purification, an area where knowledge about individual HCP behavior is still limited. We investigated the separation of different mAb formats from four individual polysorbate degrading hydrolases (CES1F, CES2C, LPLA2, and PAF-AH) using cation exchange (CEX) and mixed-mode chromatography (MMC) polishing steps. Our research identified a key challenge: The similar elution behavior of mAbs and HCPs during chromatographic separation. To investigate this phenomenon, we performed high-throughput binding screenings for recombinant polysorbate degrading hydrolases and representative mAb candidates on CEX and MMC chromatography resins. We then employed a three-step strategy that also served as a scale-up process, optimizing separation conditions and leading to the successful removal of specific HCPs while maintaining high mAb recovery rates (>96%). This strategy involved the use of surface response models and miniature columns for screening, followed by validation on larger columns using a chromatography system. Our results highlight the critical role of the inherent properties of mAbs for successful separation from HCPs. These results underscore the need to tailor the purification process to leverage the slight differences in binding behavior and elution profiles between mAbs and specific HCPs. This approach lays the foundation for developing more effective strategies for overcoming the challenge of enzymatic polysorbate degradation, paving the way for improved quality and safety in biopharmaceutical products.

Titer and charge-based heterogeneity multiattribute monitoring of mAbs in cell culture harvest using 2D ProA CEX MS

Robust monitoring of heterogeneity in biopharmaceutical development is crucial for producing safe and efficacious biotherapeutic products. Multiattribute monitoring (MAM) has emerged as an efficient tool for monitoring of mAb heterogeneities like deamidation, sialylation, glycosylation, and oxidation. Conventional biopharma analysis during mAb development relies on use of one-dimensional methods for monitoring titer and charge-based heterogeneity using non-volatile solvents without direct coupling with mass spectrometry (MS). This approach requires analysis of mAb harvest by ProA for titer estimation followed by separate cation exchange chromatography (CEX) analysis of the purified sample for estimating charge-based heterogeneity. This can take up to 60–90 min due to the required fraction collection and buffer exchange steps. In this work, a native two-dimensional liquid chromatography (2DLC) mass spectrometry method has been developed with Protein A chromatography in the first dimension for titer estimation and cation exchange chromatography (CEX) in the second dimension for charge variant analysis. The method uses volatile salts for both dimensions and enables easy coupling to MS. The proposed 2DLC method exhibits a charge variant profile that is similar to that observed via the traditional methods and takes only 15 min for mass identification of each variant. A total of six charge variants were separated by the CEX analysis after titer estimation, including linearity assessment from 5 μg to 160 μg of injected mAb sample. The proposed method successfully estimated charge variants for the mAb innovator and 4 of its biosimilars, showcasing its applicability for biosimilarity exercises. Hence, the 2D ProA CEX MS method allows direct titer and charge variant estimation of mAbs in a single workflow.

Eco-efficient downstream processing of 1,3-propanediol applicable to various fermentation processes

PDO (1,3-propanediol) is a platform chemical that is obtained by petrochemical routes and by fermentation. The latter needs relatively complex downstream processing after fermentation, due to the modest concentration of the high-boiling product, and the presence of microorganisms and many impurities in the fermentation medium. This novel research proposes an original large-scale (production capacity of 23 – 32 ktonne/y) process for the final purification of PDO and dominant by-products, from the fermentation of glucose or glycerol. Following the initial microfiltration, diafiltration, ultrafiltration and ion exchange steps, heat pump-assisted vacuum distillation was implemented to remove most of the water from the broth. Afterwards, an advanced highly-integrated dividing-wall column was designed to allow the final purification of PDO (product purity > 99.9 wt%) from light and heavy by-products. Fermentation by-products that are present in significant amounts can also be recovered and valorized. Overall, the developed final purification processes demonstrate cost-effectiveness (0.150 – 0.274 $/kg) and energy-efficiency (1.258 – 3.175 kWthh/kg) which contributes to the competitiveness of the overall downstream processing (0.256 – 0.384 $/kg and 1.487 – 3.496 kWthh/kg).

Mechanistic Insights into the Palladium-Catalyzed Perfluoroalkylative Carbonylation of Unactivated Alkenes to β-Perfluoroalkyl Esters: A DFT Study.

Transition metal-catalyzed multicomponent carbonylation is an efficient synthetic strategy to access multifunctional esters in high yields with broad functional group tolerance and good chemoselectivity. Considering the development of highly efficient synthetic methods for esters, it remains significant to grasp the mechanism of constructing multifunctional esters. Herein, density functional theoretical calculations were carried out to acquire mechanistic insight into the synthesis of β-perfluoroalkyl esters from a specific palladium-catalyzed perfluoroalkylative carbonylation of unactivated alkenes using carbon monoxide. A detailed mechanistic understanding of this reaction route includes (1) multistep radical reaction process, (2) C-C coupling and CO insertion, (3) ligand exchange, and (4) Pd-based intermediate oxidation and reductive elimination. The multistep radical process was fundamentally rationalized, including Rf· formation and radicals A and E from unactivated alkene and CO oxidation, respectively. The potential energy calculation indicated that the CO insertion into the perfluorinated alkyl radicals preceded Pd-catalyzed oxidation in the competitively multistep free radical reaction process. In addition, the I-/PhO- exchange step was predicted to be spontaneous to products. The IGMH analysis further attested to the reductive elimination process involved in the rate-determining step. Thus, a simple and valid density functional theory (DFT) approach was developed to reveal the multistep radical mechanism for the Pd-catalyzed perfluoroalkylative carbonylation of unactivated alkenes to access functional β-perfluoroalkyl esters.

Efficient synthesis of the 2-aminoimidazolium-bridged diguanosyl intermediate for nonenzymatic primer extension

Nonenzymatic genome replication has yet to be demonstrated experimentally. Recently, studies on the nonenzymatic primer extension mechanism mediated by nucleoside 5′-monophosphates (NMPs) activated with 2-aminoimidazole (2AI) have revealed that imidazolium-bridged dinucleotide intermediates (N*N) are responsible for the bulk of the chemical copying process. As a result, an efficacious synthetic pathway for producing these substrates is desirable. Standard dehydrative redox reaction between NMPs and 2AI can produce N*N in high yields for all homodimers, apart from riboguanosine 5′-monophosphate. Here, we report a vastly improved methodology for the preparation of G*G, by the introduction of a simple reverse-phase cation exchange step to increase the solubility of the mononucleotide. Our approach is more efficient, cost-effective, less time-consuming, and has better atom economy than the currently established methodology for this important molecule in primer extension studies.

Directly synthesis of H-form ZSM-5 zeolites with n-butylamine in the presence of seed and ethanol

In the research of directly synthesizing H-form ZSM-5, ammonium hydroxide is commonly used as an alkali source instead of NaOH to avoid multiple ion exchange steps. However, the volatile nature and the lack of structure-directing effect of ammonium hydroxide limit its application in practical. In this study, n-butylamine (NBA) was used as the main alkali source to directly prepare HZSM-5 zeolites with SiO2/Al2O3 ratios ranging from 40 to 300 under traditional hydrothermal conditions. The influence of the amount of NBA, ethanol, seed, and pre-crystallization on the synthesis products was investigated under the condition of SiO2/Al2O3 = 80. Theoretical simulation suggested that n-butylamine cations (NBA+) play the most potent directing role in the formation of the MFI structure but could lead to difficulties in removal during calcination. The addition of ethanol as the zeolite growth modifier (ZGM) could decrease the usage of NBA and reduce the difficulties in calcination, and the addition of seed provided the conditions for initiating crystallization in the system that could not spontaneously nucleate. HZSM-5 with different SiO2/Al2O3 ratios were prepared under the optimal crystallization conditions, and the as-synthesized samples exhibited superior textural and acid properties compared to commercial zeolite. Finally, the 1 L scale-up synthesis and MTP reaction were conducted to demonstrate the practicality of this economically and environmentally-friendly synthesis strategy.

Mechanistic study of double boron-silicon exchange reactions between dibenzosiloles and boron tribromide.

This paper describes a mechanistic study on double boron-silicon exchange reactions between dibenzosiloles and boron tribromide. This type of reaction presents a safe and environmentally benign approach to convert electron-rich siloles into corresponding electron-deficient boroles and hence shows intriguing potential for the synthesis of boron-doped π-conjugated molecular materials. However, the detailed mechanisms for such reactions have not yet been established in the current literature. In this work, we performed density functional theory (DFT) calculations in conjunction with NMR analysis to unravel the reaction pathways and energy profiles for relevant boron-silicon exchange reactions where two dibenzolesiloles and a phenanthrosilole were employed as reactants, respectively. Our results have shown that excess boron tribromide provides beneficial microsolvation effects on key transition states and reactive intermediates to lower the activation energy barrier for the overall reaction. In the meantime, the substitution pattern at the bay region of the dibenzosilole framework exerts significant impacts on the potential energy surface of the reaction; increased steric hindrance at the bay region decelerates the second boron-silicon exchange step, while extended π-conjugation at the bay region makes the first boron-silicon exchange more challenging. Overall, our computational and experimental results provide an in-depth understanding of the reactivity and scope of this type of reaction, which in turn serves as useful guidance for ongoing research in the field of borole-based organic optoelectronic materials.

An Efficient Image Encryption Method Based on Enhanced Josephus Problem and a Non-Invertible Economic Map

As an increasing number of digital images are created and transmitted over the internet, there is growing concern over their unauthorized use, which has a big impact on both security and privacy concerns. In this research, we provide a fast and secure image encryption scheme by using an enhanced Josephus problem and two-dimensional non-invertible economic chaotic map (2D-ECM) to safely and covertly protect digital image information throughout public channel transmission. First, the initial values of the 2D-ECM map are generated based on Secure Hash Algorithm (SHA-256) and the input secret key. Then, the Josephus problem is enhanced by substituting the extract operation with location exchange and dynamic start location and step size is employed to scramble the image pixels. In order to integrate the confusion process and diffusion process, the enhanced Josephus problem is utilized indirectly to choose two random columns from the scrambled image and random image to XOR them with the current column. The evaluation results prove that the proposed image cryptosystem is more efficient compared to existing cryptosystems.