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Álvarez-Asencio, RubénORCID iD iconorcid.org/0000-0002-0790-194x
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Publications (10 of 16) Show all publications
Naranjo, T., Álvarez-Asencio, R., Pedraz, P., Nieto-Ortega, B., Silva, S., Burzurí, E., . . . Pérez, E. (2020). Hydrogen-bonded host–guest systems are stable in ionic liquids. Scientific Reports, 10, Article ID 15414.
Open this publication in new window or tab >>Hydrogen-bonded host–guest systems are stable in ionic liquids
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2020 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 10, article id 15414Article in journal (Refereed) Published
Abstract [en]

We show that H-bonded host–guest systems associate in ionic liquids (ILs), pure salts with melting point below room temperature, in which dipole–dipole electrostatic interactions should be negligible in comparison with dipole-charge interactions. Binding constants (Ka) obtained from titrations of four H-bonded host–guest systems in two organic solvents and two ionic liquids yield smaller yet comparable Ka values in ionic liquids than in organic solvents. We also detect the association event using force spectroscopy, which confirms that the binding is not solely due to (de)solvation processes. Our results indicate that classic H-bonded host–guest supramolecular chemistry takes place in ILs. This implies that strong H-bonds are only moderately affected by surroundings composed entirely of charges, which can be interpreted as an indication that the balance of Coulombic to covalent forces in strong H-bonds is not tipped towards the former. © 2020, The Author(s).

Place, publisher, year, edition, pages
Nature Research, 2020
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-48923 (URN)10.1038/s41598-020-71803-3 (DOI)2-s2.0-85091293549 (Scopus ID)
Note

Funding details: VetenskapsrÃ¥det, VR, 2014-4694; Funding details: European Commission, EC; Funding details: 307609, MSCA-IF 746579; Funding details: Knut och Alice Wallenbergs Stiftelse, KAW2012.0078; Funding details: Ministerio de Economía y Competitividad, MINECO, FJCI-2015-23531, CTQ2014-60541-P, CTQ2017-86060-P; Funding details: Comunidad de Madrid, 2017-T1/IND-5562, S2013/MIT-3007; Funding details: Ministerio de Economía y Competitividad, MINECO, SEV-2016-0686; Funding text 1: We acknowledge funding for the European Union (ERC-StG-MINT 307609 and MSCA-IF 746579), the Min-isterio de Economía y Competitividad (CTQ2014-60541-P, CTQ2017-86060-P and FJCI-2015-23531), and the Comunidad de Madrid (MAD2D-CM program S2013/MIT-3007 and Programa de Atracción del Talento Inves-tigador de la Comunidad de Madrid 2017-T1/IND-5562). IMDEA Nanociencia acknowledges support from the “Severo Ochoa” Programme for Centres of Excellence in R&D (MINECO, Grant SEV-2016-0686). The Knut and Alice Wallenberg Foundation (Project number: KAW2012.0078) and the Swedish Research Council (Project number: 2014-4694) are gratefully acknowledged for their financial support.

Available from: 2020-10-14 Created: 2020-10-14 Last updated: 2023-05-25Bibliographically approved
Abitbol, T., Ahniyaz, A., Alvarez-Asencio, R., Fall, A. & Swerin, A. (2020). Nanocellulose-Based Hybrid Materials for UV Blocking and Mechanically Robust Barriers. ACS Applied Bio Materials, 3(4), 2245-2254
Open this publication in new window or tab >>Nanocellulose-Based Hybrid Materials for UV Blocking and Mechanically Robust Barriers
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2020 (English)In: ACS Applied Bio Materials, E-ISSN 2576-6422, Vol. 3, no 4, p. 2245-2254Article in journal (Refereed) Published
Abstract [en]

Nanocellulose (NC)-based hybrid coatings and films containing CeO2 and SiO2 nanoparticles (NPs) to impart UV screening and hardness properties, respectively, were prepared by solvent casting. The NC film-forming component (75 wt % of the overall solids) was composed entirely of cellulose nanocrystals (CNCs) or of CNCs combined with cellulose nanofibrils (CNFs). Zeta potential measurements indicated that the four NP types (CNC, CNF, CeO2, and SiO2) were stably dispersed in water and negatively charged at pH values between 6 and 9. The combination of NPs within this pH range ensured uniform formulations and homogeneous coatings and films, which blocked UV light, the extent of which depended on film thickness and CeO2 NP content, while maintaining good transparency in the visible spectrum (∼80%). The addition of a low amount of CNFs (1%) reduced the film hardness, but this effect was compensated by the addition of SiO2 NPs. Chiral nematic self-assembly was observed in the mixed NC film; however, this ordering was disrupted by the addition of the oxide NPs. The roughness of the hybrid coatings was reduced by the inclusion of oxide NPs into the NC matrix perhaps because the spherical oxide NPs were able to pack into the spaces between cellulose fibrils. We envision these hybrid coatings and films in barrier applications, photovoltaics, cosmetic formulations, such as sunscreens, and for the care and maintenance of wood and glass surfaces, or other surfaces that require a smooth, hard, and transparent finish and protection from UV damage.

Place, publisher, year, edition, pages
American Chemical Society, 2020
Keywords
barrier, ceria, coatings, films, nanocellulose, silica, UV, UV blocking
National Category
Engineering and Technology
Identifiers
urn:nbn:se:ri:diva-45002 (URN)10.1021/acsabm.0c00058 (DOI)2-s2.0-85084737634 (Scopus ID)
Note

Funding details: VINNOVA, 2016-04055; Funding text 1: This research was funded through a Marie Curie research fellowship (Vinnova grant 2016-04055) and the RISE NC hybrid materials competence platform.

Available from: 2020-05-27 Created: 2020-05-27 Last updated: 2023-12-06Bibliographically approved
Shimizu, M., Alvarez-Asencio, R., Niklas, N. & Uedono, A. (2020). Preparation and characterization of cellulose acetate membranes with TEMPO-oxidized cellulose nanofibrils containing alkyl ammonium carboxylates. Cellulose, 27(3), 1357-1365
Open this publication in new window or tab >>Preparation and characterization of cellulose acetate membranes with TEMPO-oxidized cellulose nanofibrils containing alkyl ammonium carboxylates
2020 (English)In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 27, no 3, p. 1357-1365Article in journal (Refereed) Published
Abstract [en]

Cellulose acetate (CA) membranes have been widely used for water purification owing to several advantages, e.g., biocompatibility and low fouling rate. However, they suffer from a lower water flux compared to the other polymeric membranes. Therefore, in this study, CA membranes were blended with 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (T-CNFs) containing quaternary alkyl ammonium (QA) carboxylates to improve their water flux. When increasing the alkyl chain length of the QAs, the positron lifetime and intensity of the CA membranes increased and decreased respectively, as revealed via positron annihilation lifetime spectroscopy. This indicated that the CA membranes had larger and fewer pores when using the T-CNFs containing QAs with longer alkyl chains. The pure water flux of these membranes also increased with the alkyl chain lengths of QAs although their rejection rate (Rj) decreased accordingly. However, they revealed a potentiality to be used as ultrafiltration membranes, allowing a 99% Rj for albumin. The tensile strength, strain to failure, and work of fracture of the CA membranes increased when blended with T-CNFs. Force measurements using the AFM colloidal probe technique showed that the adhesion between the membrane constituents depends on their surface chemistry. This indicated that the structural differences observed among the blended membranes may be due to the affinity between CA and T-CNF containing QAs with different alkyl chain lengths. This study demonstrates that the properties of CA membranes can be tailored by the addition of T-CNFs with different surface chemistries.

Place, publisher, year, edition, pages
Springer, 2020
Keywords
AFM, Cellulose acetate membrane, Cellulose nanofibril, Colloidal probe force measurement, Counter-ion, Biocompatibility, Carboxylation, Cellulose, Chain length, Colloids, Force measurement, Nanofibers, Positron annihilation spectroscopy, Positrons, Probes, Surface chemistry, Tensile strength, Colloidal probe techniques, Colloidal probes, Counterions, Nanofibril, Positron annihilation lifetime spectroscopy, Structural differences, Ultra-filtration membranes, Membranes
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-40929 (URN)10.1007/s10570-019-02872-5 (DOI)2-s2.0-85075322009 (Scopus ID)
Note

Funding details: Iwatani Naoji Foundation; Funding details: Futaba Electronics Memorial Foundation; Funding details: Ogasawara Foundation for the Promotion of Science and Engineering; Funding details: Izumi Science and Technology Foundation; Funding details: Japan Society for the Promotion of Science, JSPS; Funding details: Yazaki Memorial Foundation for Science and Technology; Funding text 1: This research was supported by Grants-in-Aid for Scientific Research (16H06912, 18K14502) from the Japan Society for the Promotion of Science and the Research Grant Program from Izumi Science and Technology Foundation, Iwatani Naoji Foundation, Futaba Electronics Memorial Foundation, Yazaki Memorial Foundation for Science and Technology, Research Institute for Production Development, and Ogasawara Foundation for the Promotion of Science & Engineering, Japan.

Available from: 2019-12-10 Created: 2019-12-10 Last updated: 2023-05-26Bibliographically approved
Alvarez-Asencio, R., Corkery, R. W. & Ahniyaz, A. (2020). Solventless synthesis of cerium oxide nanoparticles and their application in UV protective clear coatings. RSC Advances, 10(25), 14818-14825
Open this publication in new window or tab >>Solventless synthesis of cerium oxide nanoparticles and their application in UV protective clear coatings
2020 (English)In: RSC Advances, E-ISSN 2046-2069, Vol. 10, no 25, p. 14818-14825Article in journal (Refereed) Published
Abstract [en]

Colloidal dispersions of cerium oxide nanoparticles are of importance for numerous applications including as catalysts, chemical mechanical polishing agents and additives for UV protective and anticorrosion coatings. Here, concentrated oleate-coated cerium oxide nanoparticles (CeO2 NPs) with a uniform size have been produced by solventless thermolysis of cerium-oleate powder under low pressure at 320 °C and subsequently dispersed in hexane. Unlike any previously reported colloidal synthesis process for ceria nanoparticles, this process does not involve any toxic high boiling point organic solvent that requires subsequent removal at high cost. Although the process is very simple, highly concentrated cerium oxide nanoparticles with more than 17 wt% solid content and 70% of the theoretical yield can be easily obtained. Moreover, the size, shape and crystallinity of cerium oxide nanoparticles can be tailored by changing the thermal decomposition temperature and reaction time. Moreover, the new synthesis route developed in this study allows the synthesis of clean and dispersible ceria nanoparticles at a relatively low cost in a single step. The prepared ceria nanoparticles have an excellent UV absorption property and remain transparent to visible light, thus having the potential to replace potentially hazardous organic compounds in UV absorbing clear coatings. As a proof of concept, the prepared dispersions of cerium oxide nanoparticles in hexane were formulated into a solvent borne binder base to develop clear UV protecting coatings for light sensitive substrates. The general synthesis strategy presented in this study is generally applicable for the low-cost production of a concentrated dispersion of metal oxide nanoparticles with minimal environmental impact.

Keywords
Anti-corrosion coating, Cerium oxide nanoparticle, Colloidal dispersion, Hazardous organic compounds, Metal oxide nanoparticles, Solventless synthesis, Solventless thermolysis, Thermal decomposition temperature
National Category
Engineering and Technology
Identifiers
urn:nbn:se:ri:diva-44990 (URN)10.1039/d0ra01710h (DOI)2-s2.0-85083627169 (Scopus ID)
Available from: 2020-05-22 Created: 2020-05-22 Last updated: 2023-05-09Bibliographically approved
Karlsson, M., Álvarez-Asencio, R., Bordes, R., Larsson, A., Taylor, P. & Steenari, B.-M. (2019). Characterization of paint formulated using secondary TiO2 pigments recovered from waste paint. JCT Research, 16(2), 607-614
Open this publication in new window or tab >>Characterization of paint formulated using secondary TiO2 pigments recovered from waste paint
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2019 (English)In: JCT Research, ISSN 1547-0091, E-ISSN 2168-8028, Vol. 16, no 2, p. 607-614Article in journal (Refereed) Published
Abstract [en]

The paint industry is continuously striving to reduce its environmental impact, especially when it comes to the major virgin white pigment, titanium dioxide (TiO2). In this work, recycled TiO2 pigment was used in a paint formulation as a replacement for pigment made from virgin raw materials. The paint was evaluated based on pH, Stormer and ICI viscosities, gloss, hiding power, and color characteristics. The paint films were also characterized by LVSEM–EDS, AFM, and profilometry. The most significant difference between a paint based on recycled pigments and a paint based on virgin pigments was the agglomeration of pigment particles which gave a reduction in gloss and a rougher surface of the dried paint film based on recycled pigment, and it could be concluded that the recycled pigment could not be used without accepting a small decrease in paint quality. This points toward two main directions: (1) the use of recycled pigment in applications with less demand on surface finish and gloss, such as ceiling paints, and (2) that further work on formulation should be carried out with the recycled pigment as for any other new pigment introduced in a paint formulation to optimize its performance. © 2018, The Author(s).

Keywords
Paint, Recycling, TiO2, Waste, Environmental impact, Titanium dioxide, Wastes, Ceiling paints, Color characteristics, Paint formulation, Pigment particles, Surface finishes, Titanium dioxides (TiO2), White pigments
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36614 (URN)10.1007/s11998-018-0132-x (DOI)2-s2.0-85056581969 (Scopus ID)
Available from: 2018-12-06 Created: 2018-12-06 Last updated: 2021-06-18Bibliographically approved
Álvarez-Asencio, R., Moreno-Ramírez, J. S., Pimentel, C., Casado, S., Matta, M., Gierschner, J., . . . Pina, C. M. (2017). Molecular-scale shear response of the organic semiconductor β -DBDCS (100) surface. Physical Review B, 96(11), Article ID 115422.
Open this publication in new window or tab >>Molecular-scale shear response of the organic semiconductor β -DBDCS (100) surface
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2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 11, article id 115422Article in journal (Refereed) Published
Abstract [en]

In this work we present friction-force microscopy (FFM) lattice-resolved images acquired on the (100) facet of the semiconductor organic oligomer (2Z,2′Z)-3,3′-(1,4-phenylene)bis(2-(4-butoxyphenyl)acrylonitrile) (β-DBDCS) crystal in water at room temperature. Stick-slip contrast, lateral contact stiffness, and friction forces are found to depend strongly on the sliding direction due to the anisotropic packing of the molecular chains forming the crystal surface along the [010] and [001] directions. The anisotropy also causes the maximum value of the normal force applicable before wearing to increase by a factor of 3 when the scan is performed along the [001] direction on the (100) face. Altogether, our results contribute to achieving a better understanding of the molecular origin of friction anisotropy on soft crystalline surfaces, which has been often hypothesized but rarely investigated in the literature.

National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-33145 (URN)10.1103/PhysRevB.96.115422 (DOI)2-s2.0-85030108885 (Scopus ID)
Available from: 2018-01-31 Created: 2018-01-31 Last updated: 2021-06-18Bibliographically approved
Nyström, L., Álvarez-Asencio, R., Frenning, G., Saunders, B. R., Rutland, M. W. & Malmsten, M. (2016). Electrostatic swelling transitions in surface-bound microgels. ACS Applied Materials and Interfaces, 8(40), 27129-27139
Open this publication in new window or tab >>Electrostatic swelling transitions in surface-bound microgels
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2016 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 40, p. 27129-27139Article in journal (Refereed) Published
Abstract [en]

Herein, electrostatic swelling transitions of poly(ethyl acrylate-co-methacrylic acid) microgels covalently bound to silica surfaces are investigated. Confined at a solid surface, microgel swelling is anisotropically hindered and the structure is flattened to an extent dictated by pH and microgel composition. Microgel deformation under applied load is also shown to depend on microgel charge density, with the highest deformation observed at intermediate charge densities. Two modes of microgel deformation under load were observed, one elastic and one viscoelastic, related to polymer strand deformation and displacement of trapped water, respectively. Results on polymer strand dynamics reveal that the microgels are highly dynamic, as the number of strand-tip interaction points increases 4-fold during a 10 s contact time. Furthermore, finite element modeling captures these effects qualitatively and shows that stress propagation in the microgel network decays locally at the rim of contact with a solid interface or close to the tip probe. Taken together, the results demonstrate a delicate interplay between the surface and microgel which determines the structure and nanomechanical properties of the latter and needs to be controlled in applications of systems such as pH-responsive surface coatings in biomaterials.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
Keywords
atomic force, microscopy, finite element method, microgel, pH-responsive, quartz crystal microbalance, surface-bound
National Category
Physical Chemistry
Identifiers
urn:nbn:se:ri:diva-13630 (URN)10.1021/acsami.6b09751 (DOI)2-s2.0-84991627600 (Scopus ID)
Available from: 2016-10-07 Created: 2016-10-07 Last updated: 2023-05-25Bibliographically approved
Nyström, L., Nordström, R., Bramhill, J., Saunders, B. R., Álvarez-Asencio, R., Rutland, M. W. & Malmsten, M. (2016). Factors affecting peptide interactions with surface-bound microgels. Biomacromolecules, 17(2), 669-678
Open this publication in new window or tab >>Factors affecting peptide interactions with surface-bound microgels
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2016 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, no 2, p. 669-678Article in journal (Refereed) Published
Abstract [en]

Effects of electrostatics and peptide size on peptide interactions with surface-bound microgels were investigated with ellipsometry, confocal microscopy, and atomic force microscopy (AFM). Results show that binding of cationic poly-l-lysine (pLys) to anionic, covalently immobilized, poly(ethyl acrylate-co-methacrylic acid) microgels increased with increasing peptide net charge and microgel charge density. Furthermore, peptide release was facilitated by decreasing either microgel or peptide charge density. Analogously, increasing ionic strength facilitated peptide release for short peptides. As a result of peptide binding, the surface-bound microgels displayed pronounced deswelling and increased mechanical rigidity, the latter quantified by quantitative nanomechanical mapping. While short pLys was found to penetrate the entire microgel network and to result in almost complete charge neutralization, larger peptides were partially excluded from the microgel network, forming an outer peptide layer on the microgels. As a result of this difference, microgel flattening was more influenced by the lower Mw peptide than the higher. Peptide-induced deswelling was found to be lower for higher Mw pLys, the latter effect not observed for the corresponding microgels in the dispersed state. While the effects of electrostatics on peptide loading and release were similar to those observed for dispersed microgels, there were thus considerable effects of the underlying surface on peptide-induced microgel deswelling, which need to be considered in the design of surface-bound microgels as carriers of peptide loads, for example, in drug delivery or in functionalized biomaterials.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
National Category
Other Chemistry Topics Physical Chemistry Pharmaceutical Sciences
Identifiers
urn:nbn:se:ri:diva-93 (URN)10.1021/acs.biomac.5b01616 (DOI)2-s2.0-84957900932 (Scopus ID)
Available from: 2016-05-31 Created: 2016-04-28 Last updated: 2023-05-25Bibliographically approved
Álvarez-Asencio, R., Wallqvist, V., Kjellin, M., Rutland, M. W., Camacho, A., Niklas, N. & Luengo, G. S. (2016). Nanomechanical properties of human skin and introduction of a novel hair indenter. Journal of The Mechanical Behavior of Biomedical Materials, 54, 185-193
Open this publication in new window or tab >>Nanomechanical properties of human skin and introduction of a novel hair indenter
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2016 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 54, p. 185-193Article in journal (Refereed) Published
Abstract [en]

The mechanical resistance of the stratum corneum, the outermost layer of skin, to deformation has been evaluated at different length scales using Atomic Force Microscopy. Nanomechanical surface mapping was first conducted using a sharp silicon tip and revealed that Young’s modulus of the stratum corneum varied over the surface with a mean value of about 0.4 GPa. Force indentation measurements showed permanent deformation of the skin surface only at high applied loads (above 4 μN). The latter effect was further demonstrated using nanomechanical imaging in which the obtained depth profiles clearly illustrate the effects of increased normal force on the elastic/plastic surface deformation. Force measurements utilizing the single hair fiber probe supported the nanoindentation results of the stratum corneum being highly elastic at the nanoscale, but revealed that the lateral scale of the deformation determines the effective elastic modulus.This result resolves the fact that the reported values in the literature vary greatly and will help to understand the biophysics of the interaction of razor cut hairs that curl back during growth and interact with the skin.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Atomic Force Microscopy, Hair, Mechanical properties, Stratum corneum
National Category
Other Chemistry Topics Biophysics Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:ri:diva-107 (URN)10.1016/j.jmbbm.2015.09.014 (DOI)2-s2.0-84944111754 (Scopus ID)
Available from: 2016-04-28 Created: 2016-04-28 Last updated: 2023-06-08Bibliographically approved
Ghalgaoui, A., Shimizu, R., Hosseinpour, S., Alvarez-Asencio, R., McKee, C. T., Johnson, C. M. & Rutland, M. (2014). Monolayer study by VSFS: In situ response to compression and shear in a contact (ed.). Langmuir, 30(11), 3075-3085
Open this publication in new window or tab >>Monolayer study by VSFS: In situ response to compression and shear in a contact
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2014 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 11, p. 3075-3085Article in journal (Refereed) Published
Abstract [en]

Self-assembled octadecyltrichlorosilane ((OTS), CH3(CH 2)17SiCl3) layers on hydroxyl-terminated silicon oxide (SiO2) were prepared. The monolayers were characterized with atomic force microscopy (AFM) and contact angle measurements; their conformation was studied before, during, and after contact with a polymer (either PDMS or PTFE) surface using the vibrational sum frequency spectroscopy (VSFS) technique. During contact, the effect of pressure was studied for both polymer surfaces, but in the case of PTFE, the effect of shear rate on the contact was simultaneously studied. The VSFS response of the monolayers with pressure was almost entirely due to changes in the real area of contact with the polymer and therefore the Fresnel factors, whereas sliding caused disorder in the previously all-trans monolayer, as evidenced by a significant increase in the population of gauche defects.

National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-6735 (URN)10.1021/la4042474 (DOI)2-s2.0-84897094136 (Scopus ID)23756 (Local ID)23756 (Archive number)23756 (OAI)
Available from: 2016-09-08 Created: 2016-09-08 Last updated: 2021-06-18Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-0790-194x

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