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Keywords = icosahedral phases

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18 pages, 6263 KiB  
Article
Orientation Relationship of the Intergrowth Al13Fe3 and Al13Fe4 Intermetallics Determined by Single-Crystal X-ray Diffraction
by Yibo Liu, Changzeng Fan, Zhefeng Xu, Ruidong Fu, Bin Wen and Lifeng Zhang
Metals 2024, 14(4), 463; https://doi.org/10.3390/met14040463 - 15 Apr 2024
Cited by 6 | Viewed by 2091
Abstract
In the Al-Fe binary system, the Al13Fe3 phase as well as the Al13Fe4 phase has similar icosahedral building blocks like those appearing in quasicrystals. Therefore, it is of vital importance to clarify the formation process of these [...] Read more.
In the Al-Fe binary system, the Al13Fe3 phase as well as the Al13Fe4 phase has similar icosahedral building blocks like those appearing in quasicrystals. Therefore, it is of vital importance to clarify the formation process of these two phases. Coexistence of the Al13Fe3 and Al13Fe4 phases was discovered from the educts obtained with a nominal atomic ratio of Al/Fe of 9:2 by high-pressure sintering for the first time. Firstly, single crystal X-ray diffraction (SXRD) combined with a scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX) measurement capabilities were adopted to determine the detailed crystal structures of both phases, which were sharply refined with regard to Al13Fe3 and Al13Fe4. Secondly, the orientation relationship between Al13Fe3 and Al13Fe4 was directly deduced from the SXRD datasets and the coexistence structure model was consequently constructed. Finally, seven pairs of parallel atomic planes and their unique orientation relations were determined from the reconstructed reciprocal space precession images. In addition, the real space structure model of the intergrowth crystal along with one kind of interfacial atomic structure were constructed from the determined orientation relations between two phases. Full article
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10 pages, 1110 KiB  
Communication
Effect of Alloying Elements on the Short-Range Orders and Atomic Diffusion Behavior of Liquid Al−9Si Cast Alloys
by Xunming Zhu, Dan Liu, Jian Wang, Candong Chen, Xinxin Li, Li Wang and Mingxu Wang
Materials 2023, 16(20), 6768; https://doi.org/10.3390/ma16206768 - 19 Oct 2023
Cited by 3 | Viewed by 1420
Abstract
To investigate the influence of alloying elements (Zn, Mg, and Cu) on the structural and dynamical properties of liquid Al−9Si alloy, we conducted ab initio molecular dynamics (AIMD) simulations. Our results indicate that the structure of Al−Si−M ternary alloys is determined with a [...] Read more.
To investigate the influence of alloying elements (Zn, Mg, and Cu) on the structural and dynamical properties of liquid Al−9Si alloy, we conducted ab initio molecular dynamics (AIMD) simulations. Our results indicate that the structure of Al−Si−M ternary alloys is determined with a combination of atomic radii and mixing enthalpy, while the dynamic properties are primarily influenced by electronic structure of the alloying elements. Specifically, the addition of Cu promotes the formation of Al−Cu short-range order (SRO), while Zn has a higher propensity for Zn−Zn SRO. The Al−Cu SRO in liquid alloy may serve as the precursor for the Al2Cu reinforcing phase in Al−Si−Cu alloys. Upon the addition of Mg, a greater number of relatively stable perfect and distorted icosahedral structures, as well as hcp and bcc ordered structures with lower energies, are observed. Additionally, the presence of Mg leads to a reduction in the atomic diffusion rates of Al and Si, while Cu and Zn exhibit complex diffusion behavior influenced by the presence of Si atoms. Full article
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11 pages, 2895 KiB  
Article
Investigation of the Processes of Structure Formation during Explosion Welding of Copper and Molybdenum
by Fedor M. Noskov, Lyudmila I. Kveglis, Vyacheslav I. Mali, Maksim A. Esikov and Rimma Y. Sakenova
Crystals 2023, 13(10), 1514; https://doi.org/10.3390/cryst13101514 - 19 Oct 2023
Viewed by 1583
Abstract
This article examines the processes of structure formation occurring during joint plastic deformation by the explosion of copper and molybdenum. These components are dissimilar metals with very limited mutual solubility under normal conditions, and the circumstances allowing for their interaction, as well as [...] Read more.
This article examines the processes of structure formation occurring during joint plastic deformation by the explosion of copper and molybdenum. These components are dissimilar metals with very limited mutual solubility under normal conditions, and the circumstances allowing for their interaction, as well as the products of the mechanochemical reactions of such interactions, have not been sufficiently studied and require new approaches. A cluster approach was used to describe the processes of structure formation, which describes phase formation as the process transitioning of the polyhedron of the initial phase into the polyhedron of the final phase. This work shows that under the conditions under consideration, not only is the formation of solid solutions in the contact zone with smooth concentration transitions from one component to another possible, but also the formation of new structural states, which can be represented as localized icosahedral atomic configurations (amorphous metal clusters). Such a structure is capable of locally strengthening the composite, which is confirmed by microhardness studies. Full article
(This article belongs to the Topic Advanced Structural Crystals)
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26 pages, 21730 KiB  
Article
Genome Characterization and Infectivity Potential of Vibriophage-ϕLV6 with Lytic Activity against Luminescent Vibrios of Penaeus vannamei Shrimp Aquaculture
by Manikantha Benala, Murugadas Vaiyapuri, Visnuvinayagam Sivam, Karthika Raveendran, Mukteswar Prasad Mothadaka and Madhusudana Rao Badireddy
Viruses 2023, 15(4), 868; https://doi.org/10.3390/v15040868 - 28 Mar 2023
Cited by 10 | Viewed by 4335
Abstract
Shrimp aquaculture, especially during the hatchery phase, is prone to economic losses due to infections caused by luminescent vibrios. In the wake of antimicrobial resistance (AMR) in bacteria and the food safety requirements of farmed shrimp, aqua culturists are seeking alternatives to antibiotics [...] Read more.
Shrimp aquaculture, especially during the hatchery phase, is prone to economic losses due to infections caused by luminescent vibrios. In the wake of antimicrobial resistance (AMR) in bacteria and the food safety requirements of farmed shrimp, aqua culturists are seeking alternatives to antibiotics for shrimp health management, and bacteriophages are fast emerging as natural and bacteria-specific antimicrobial agents. This study analyzed the whole genome of vibriophage-ϕLV6 that showed lytic activity against six luminescent vibrios isolated from the larval tanks of P. vannamei shrimp hatcheries. The Vibriophage-ϕLV6 genome was 79,862 bp long with 48% G+C content and 107 ORFs that coded for 31 predicted protein functions, 75 hypothetical proteins, and a tRNA. Pertinently, the vibriophage-ϕLV6 genome harbored neither AMR determinants nor virulence genes, indicating its suitability for phage therapy. There is a paucity of whole genome-based information on vibriophages that lyse luminescent vibrios, and this study adds pertinent data to the database of V. harveyi infecting phage genomes and, to our knowledge, is the first vibriophage genome report from India. Transmission electron microscopy (TEM) of vibriophage-ϕLV6 revealed an icosahedral head (~73 nm) and a long, flexible tail (~191 nm) suggesting siphovirus morphology. The vibriophage-ϕLV6 phage at a multiplicity of infection (MOI) of 80 inhibited the growth of luminescent V. harveyi at 0.25%, 0.5%, 1%, 1.5%, 2%, 2.5%, and 3% salt gradients. In vivo experiments conducted with post-larvae of shrimp showed that vibriophage-ϕLV6 reduced luminescent vibrio counts and post-larval mortalities in the phage-treated tank compared to the bacteria-challenged tank, suggesting the potentiality of vibriophage-ϕLV6 as a promising candidate in treating luminescent vibriosis in shrimp aquaculture. The vibriophage-ϕLV6 survived for 30 days in salt (NaCl) concentrations ranging from 5 ppt to 50 ppt and was stable at 4 °C for 12 months. Full article
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16 pages, 6982 KiB  
Article
Computational Insights into Ru, Pd and Pt fcc Nano-Catalysts from Density Functional Theory Calculations: The Influence of Long-Range Dispersion Corrections
by Marietjie J. Ungerer and Nora H. De Leeuw
Catalysts 2022, 12(10), 1287; https://doi.org/10.3390/catal12101287 - 21 Oct 2022
Cited by 5 | Viewed by 4050
Abstract
Ruthenium, palladium and platinum fall within the group of noble metals that are widely used in catalysis, especially for the electrocatalytic production of hydrogen. The dominant phase of the bulk Ru metal is hexagonal close-packed (hcp), which has been studied extensively. [...] Read more.
Ruthenium, palladium and platinum fall within the group of noble metals that are widely used in catalysis, especially for the electrocatalytic production of hydrogen. The dominant phase of the bulk Ru metal is hexagonal close-packed (hcp), which has been studied extensively. However, significantly less attention has been paid to the face-centred cubic (fcc) phases, which have been observed in nanoparticles. In this study, we have carried out density functional theory calculations with long-range dispersion corrections [DFT-D2, DFT-D3 and DFT-D3-(BJ)] to investigate the lattice parameters, surface energies and work functions of the (001), (011) and (111) surfaces of Ru, Pd and Pt in the fcc phase. When investigating the surface properties of the three metals, we observed that the DFT-D2 method generally underestimated the lattice parameters by up to 2.2% for Pt and 2.8% for Ru. The surface energies followed the observed trend (111) < (001) < (011) for both Ru and Pd with all three methods, which is comparable to experimental data. For Pt the same trend was observed with DFT-D2 and DFT-D3(BJ), but it deviated to Pt (111) < Pt (011) < Pt (001) for the DFT-D3 method. DFT-D2 overestimated the surface energies for all three Miller Indexes by 82%, 73%, and 60%, when compared to experimental values. The best correlation for the surface energies was obtained with the DFT-D3 and DFT-D3(BJ) methods, both of which have deviate by less than 15% deviation for all surfaces with respect to experiment. The work function followed the trend of Φ (111) < Φ (001) < Φ (011) for all three metals and calculated by all three methods. Five different types of Ru, Pd and Pt nanoparticles were considered, including icosahedral, decahedral, cuboctahedral, cubic and spherical particles of different sizes. The bulk, surface and nanoparticle calculations showed that the DFT-D2 method for Pt overestimated the exchange-correlation, leading to higher energy values that can be contributed erroneously to a more stable structure. The calculations showed that as soon as the surface-to-bulk ratio > 1, the energy per atom resembles bulk energy values. Full article
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8 pages, 3671 KiB  
Article
Physical Properties of Ti45Zr38Fe17 Alloy and Its Amorphous Hydride
by Antoni Żywczak, Łukasz Gondek, Joanna Czub, Piotr Janusz, Nivas Babu Selvaraj and Akito Takasaki
Energies 2022, 15(12), 4236; https://doi.org/10.3390/en15124236 - 9 Jun 2022
Cited by 1 | Viewed by 2222
Abstract
The alloys based on Ti-Zr are considered an excellent candidate for hydrogen storage applications. In this communication, we report the results of Fe substitution for Ni in the well-known Ti45Zr38Ni17 compound. The parent and related compounds can be [...] Read more.
The alloys based on Ti-Zr are considered an excellent candidate for hydrogen storage applications. In this communication, we report the results of Fe substitution for Ni in the well-known Ti45Zr38Ni17 compound. The parent and related compounds can be obtained as amorphous powders, transforming into the quasicrystalline phase (i-phase) after annealing. The amorphous Ti45Zr38Fe17 phase is transformed into the icosahedral quasicrystalline state, and it is a quasi-continuous process. The i-phase is well-developed close to 500 °C. At higher temperatures, the quasicrystal structure transforms into the other phase: the w-phase (an approximant to the crystalline phase) and another crystal phase with a small addition of the FeZr3 and the Fe2(ZrTi)3. The amorphous Ti45Zr38Fe17 phases can be hydrogenated while maintaining the amorphous nature, which constitutes another very fascinating research field for our group. The investigated alloy shows a good capacity for gaseous H2 at level 2.54 wt.% at elevated temperatures. The ferromagnetic signal of the amorphous TiZrFe comes from magnetic nanocrystallites in the amorphous matrix. After heating, the magnetic signal significantly decreases due to the lack of long-range magnetic ordering in the i-phase of the Ti45Zr38Fe17 alloy. Full article
(This article belongs to the Topic Hydrogen Energy Technologies)
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16 pages, 3731 KiB  
Article
Powder Metallurgical Processing of Sn-Reinforced Al-Cu-Fe Quasicrystals: Structure, Microstructure and Toughening Behavior
by Yagnesh Shadangi, Vikas Shivam, Kausik Chattopadhyay and Nilay Krishna Mukhopadhyay
J. Manuf. Mater. Process. 2022, 6(3), 60; https://doi.org/10.3390/jmmp6030060 - 31 May 2022
Cited by 22 | Viewed by 3428
Abstract
The present work deals with powder metallurgical processing of Sn-reinforced Al-Cu-Fe icosahedral quasicrystalline (IQC) composites processed through mechanical milling (MM) followed by hot pressing and pressureless sintering. The structure, microstructure and toughening behavior of the nanocomposite powders and bulk samples were investigated through [...] Read more.
The present work deals with powder metallurgical processing of Sn-reinforced Al-Cu-Fe icosahedral quasicrystalline (IQC) composites processed through mechanical milling (MM) followed by hot pressing and pressureless sintering. The structure, microstructure and toughening behavior of the nanocomposite powders and bulk samples were investigated through X-ray diffraction (XRD), optical metallography (OM), scanning electron microscopy (SEM) and indentation techniques. The XRD pattern suggested the coexistence of IQC and λ-Al13Fe4 (mC102; a = 1.549 nm, b = 0.808 nm, c = 1.248 nm) and B2-type Al (Cu, Fe) (cP2; a = 0.29 nm) crystalline phases in milled as well as sintered samples. The face-centered icosahedral (FCI) ordering was persistent even after 40 h of milling and sintering. The structural transformation during MM influences the indentation behavior of IQC-Sn nanocomposite powders, and the microhardness was found to be in the range of ~5.3 to 7.3 GPa. Further, efforts were made to study the indentation behavior of IQC-Sn composite prepared by pressureless sintering and hot pressing. The fracture toughness of the IQC-10Sn hot-pressed sample was found to be ~1.92 MPa.m, which is ~22% higher than that of the as-cast and annealed IQC. The enhancement in the fracture toughness resulted mainly from the inhibition of cracks by Sn reinforcement particles. This suggests that powder metallurgical processing can produce the IQC-Sn composite with an optimal combination of microhardness and fracture toughness. Full article
(This article belongs to the Special Issue Powder Metallurgy and Additive Manufacturing/3D Printing of Materials)
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18 pages, 31207 KiB  
Article
Microstructure and Properties after Friction Stir Processing of Twin-Roll Cast Al–Mn–Cu–Be Alloy
by Matjaž Macerl, Franc Zupanič, Lara Hočuršćak, Damjan Klobčar, András Kovács and Tonica Bončina
Crystals 2022, 12(5), 630; https://doi.org/10.3390/cryst12050630 - 27 Apr 2022
Cited by 4 | Viewed by 2311
Abstract
We studied the effect of friction stir processing (FSP) on the microstructure and properties of high-speed twin-roll cast strips made of an experimental Al–Mn–Cu–Be alloy. The samples were examined using light, scanning, and transmission electron microscopy, microchemical analysis, X-ray diffraction, and indentation testing. [...] Read more.
We studied the effect of friction stir processing (FSP) on the microstructure and properties of high-speed twin-roll cast strips made of an experimental Al–Mn–Cu–Be alloy. The samples were examined using light, scanning, and transmission electron microscopy, microchemical analysis, X-ray diffraction, and indentation testing. During FSP, the rotational speed varied, while other parameters remained constant. The uniformity of the microstructure increased with the growing rotational speed. In the stir zone, several processes took place, and the most important were: recrystallisation of the matrix grains, fragmentation of the primary intermetallic particles Al15Mn3Be2 and their more uniform distribution in the stir zone, fracture, and dispersion of the eutectic icosahedral quasicrystalline phase (IQC), transformation of tiny Al15Mn3Be2 and IQC particles into the τ1-Al26Mn6Cu4 phase and precipitation of Al–Mn–Cu precipitates. In the thermomechanically affected zone, new dislocations formed as well as dispersion of the IQC eutectic phase and recrystallisation of the matrix grains. In the heat-affected zone, dissolution of θ’-Al2Cu precipitates occurred. The hardness variation was not severe between the stir and heat-affected zones. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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14 pages, 3569 KiB  
Article
Construction of Al-Mg-Zn Interatomic Potential and the Prediction of Favored Glass Formation Compositions and Associated Driving Forces
by Bei Cai, Jiahao Li, Wensheng Lai, Jianbo Liu and Baixin Liu
Materials 2022, 15(6), 2062; https://doi.org/10.3390/ma15062062 - 11 Mar 2022
Cited by 3 | Viewed by 2534
Abstract
An interatomic potential is constructed for the ternary Al-Mg-Zn system under a proposed modified tight-binding scheme, and it is verified to be realistic. Applying this ternary potential, atomistic simulations predict an intrinsic glass formation region in the composition triangle, within which the glassy [...] Read more.
An interatomic potential is constructed for the ternary Al-Mg-Zn system under a proposed modified tight-binding scheme, and it is verified to be realistic. Applying this ternary potential, atomistic simulations predict an intrinsic glass formation region in the composition triangle, within which the glassy alloys are more energetically favored in comparison with their solid solution counterparts. Kinetically, the amorphization driving force of each disordered state is derived to correlate the readiness of its glass-forming ability in practice; thus, an optimal stoichiometry region is pinpointed around Al35Mg35Zn30. Furthermore, by monitoring the structural evolution for various (Al50Mg50)1−xZnx (x = 30, 50, and 70 at.%) compositions, the optimized-glass-former Al35Mg35Zn30 is characterized by both the highest degree of icosahedral ordering and the highest phase stability among the investigated compositions. In addition, the icosahedral network in Al35Mg35Zn30 exhibits a much higher cross-linking degree than that in Al25Mg25Zn50. This suggests that there is a certain correlation between the icosahedral ordering and the larger glass-forming ability of Al35Mg35Zn30. Our results have significant implications in clarifying glass formation and hierarchical atomic structures, and in designing new ternary Al-Mg-Zn glassy alloys with high GFA. Full article
(This article belongs to the Topic Advanced Forming Technology of Metallic Materials)
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16 pages, 10927 KiB  
Article
Microstructure and Indentation Properties of Single-Roll and Twin-Roll Casting of a Quasicrystal-Forming Al-Mn-Cu-Be Alloy
by Franc Zupanič, Matjaž Macerl, Toshio Haga and Tonica Bončina
Metals 2022, 12(2), 187; https://doi.org/10.3390/met12020187 - 20 Jan 2022
Cited by 3 | Viewed by 2033
Abstract
In this investigation, strips of an experimental Al-Mn-Cu-Be alloy were manufactured by high-speed single-roll and twin-roll casting to stimulate the formation of a quasicrystalline phase during solidification. The strips were characterised by light microscopy, scanning and transmission electron microscopy, microchemical analysis, and X-ray [...] Read more.
In this investigation, strips of an experimental Al-Mn-Cu-Be alloy were manufactured by high-speed single-roll and twin-roll casting to stimulate the formation of a quasicrystalline phase during solidification. The strips were characterised by light microscopy, scanning and transmission electron microscopy, microchemical analysis, and X-ray diffraction. Indentation testing was used to determine the mechanical responses of the strips in different areas. A smooth surface was achieved on both sides of the twin-roll-cast strip, while the free surface of the single-roll-cast strip was rough. The microstructures in both strips consisted of an Al-rich solid solution matrix embedding several intermetallic phases Θ-Al2Cu, Be4Al (Mn, Cu), Al15Mn3Be2 and icosahedral quasicrystalline phase (IQC). The microstructure of the single-roll-cast strip was more uniform than that of the twin-roll-cast strip. Coarse Al15Mn3Be2 particles appeared in both alloys, especially at the centre of the twin-roll strip. These coarse particles adversely affected the strength and ductility. Nevertheless, both casting methods provided high-cooling rates, enabling the formation of metastable phases, such as quasicrystals. However, improvements in alloy composition and casting procedure are required to obtain enhanced microstructures and properties. Full article
(This article belongs to the Special Issue Structure and Properties of Aluminium Alloys 2023)
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23 pages, 2505 KiB  
Review
Kaposi’s Sarcoma-Associated Herpesvirus, the Etiological Agent of All Epidemiological Forms of Kaposi’s Sarcoma
by Aude Jary, Marianne Veyri, Adélie Gothland, Valentin Leducq, Vincent Calvez and Anne-Geneviève Marcelin
Cancers 2021, 13(24), 6208; https://doi.org/10.3390/cancers13246208 - 9 Dec 2021
Cited by 21 | Viewed by 5852
Abstract
Kaposi’s sarcoma-associated herpesvirus (KSHV), also called human herpesvirus 8 (HHV-8), is an oncogenic virus belonging to the Herpesviridae family. The viral particle is composed of a double-stranded DNA harboring 90 open reading frames, incorporated in an icosahedral capsid and enveloped. The viral cycle [...] Read more.
Kaposi’s sarcoma-associated herpesvirus (KSHV), also called human herpesvirus 8 (HHV-8), is an oncogenic virus belonging to the Herpesviridae family. The viral particle is composed of a double-stranded DNA harboring 90 open reading frames, incorporated in an icosahedral capsid and enveloped. The viral cycle is divided in the following two states: a short lytic phase, and a latency phase that leads to a persistent infection in target cells and the expression of a small number of genes, including LANA-1, v-FLIP and v-cyclin. The seroprevalence and risk factors of infection differ around the world, and saliva seems to play a major role in viral transmission. KSHV is found in all epidemiological forms of Kaposi’s sarcoma including classic, endemic, iatrogenic, epidemic and non-epidemic forms. In a Kaposi’s sarcoma lesion, KSHV is mainly in a latent state; however, a small proportion of viral particles (<5%) are in a replicative state and are reported to be potentially involved in the proliferation of neighboring cells, suggesting they have crucial roles in the process of tumorigenesis. KSHV encodes oncogenic proteins (LANA-1, v-FLIP, v-cyclin, v-GPCR, v-IL6, v-CCL, v-MIP, v-IRF, etc.) that can modulate cellular pathways in order to induce the characteristics found in all cancer, including the inhibition of apoptosis, cells’ proliferation stimulation, angiogenesis, inflammation and immune escape, and, therefore, are involved in the development of Kaposi’s sarcoma. Full article
(This article belongs to the Special Issue Perspectives on Kaposi's Sarcoma)
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19 pages, 4887 KiB  
Review
Current Progress in the Development of Hepatitis B Virus Capsid Assembly Modulators: Chemical Structure, Mode-of-Action and Efficacy
by Hyejin Kim, Chunkyu Ko, Joo-Youn Lee and Meehyein Kim
Molecules 2021, 26(24), 7420; https://doi.org/10.3390/molecules26247420 - 7 Dec 2021
Cited by 33 | Viewed by 6484
Abstract
Hepatitis B virus (HBV) is a major causative agent of human hepatitis. Its viral genome comprises partially double-stranded DNA, which is complexed with viral polymerase within an icosahedral capsid consisting of a dimeric core protein. Here, we describe the effects of capsid assembly [...] Read more.
Hepatitis B virus (HBV) is a major causative agent of human hepatitis. Its viral genome comprises partially double-stranded DNA, which is complexed with viral polymerase within an icosahedral capsid consisting of a dimeric core protein. Here, we describe the effects of capsid assembly modulators (CAMs) on the geometric or kinetic disruption of capsid construction and the virus life cycle. We highlight classical, early-generation CAMs such as heteroaryldihydropyrimidines, phenylpropenamides or sulfamoylbenzamides, and focus on the chemical structure and antiviral efficacy of recently identified non-classical CAMs, which consist of carboxamides, aryl ureas, bithiazoles, hydrazones, benzylpyridazinones, pyrimidines, quinolines, dyes, and antimicrobial compounds. We summarize the therapeutic efficacy of four representative classical compounds with data from clinical phase 1 studies in chronic HBV patients. Most of these compounds are in phase 2 trials, either as monotherapy or in combination with approved nucleos(t)ides drugs or other immunostimulatory molecules. As followers of the early CAMs, the therapeutic efficacy of several non-classical CAMs has been evaluated in humanized mouse models of HBV infection. It is expected that these next-generation HBV CAMs will be promising candidates for a series of extended human clinical trials. Full article
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18 pages, 4823 KiB  
Article
Dual Cluster Model for Medium-Range Order in Metallic Glasses
by Masato Shimono and Hidehiro Onodera
Metals 2021, 11(11), 1840; https://doi.org/10.3390/met11111840 - 16 Nov 2021
Cited by 2 | Viewed by 2832
Abstract
The atomic structure of medium-range order in metallic glasses is investigated by using molecular dynamics (MD) simulations. Glass formation processes were simulated by rapid cooling from liquid phases of a model binary alloy system of different-sized elements. Two types of short-range order of [...] Read more.
The atomic structure of medium-range order in metallic glasses is investigated by using molecular dynamics (MD) simulations. Glass formation processes were simulated by rapid cooling from liquid phases of a model binary alloy system of different-sized elements. Two types of short-range order of atomic clusters with the five-fold symmetry are found in glassy phases: icosahedral clusters (I-clusters) formed around the smaller-sized atoms and Frank–Kasper clusters (i.e., Z14, Z15, and Z16 clusters (Z-clusters)) formed around the bigger-sized atoms. Both types of clusters (I-and Z-clusters) are observed even in liquid phases and the population of them goes up as the temperature goes down. A considerable atomic size difference between alloying elements would enhance the formation of both the I- and Z-clusters. In glassy phases, the I- and Z-clusters are mutually connected to form a complicated network, and the network structure becomes denser as the structural relaxation goes on. In the network, the medium-range order is mainly constructed by the volume sharing type connection between I- and Z-clusters. Following Nelson’s disclination theory, the network structure can be understood as a random network of Z-clusters, which is complimentarily surrounded by another type of network formed by I-clusters. Full article
(This article belongs to the Special Issue Structure and Properties of Amorphous Metallic Alloys)
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45 pages, 6964 KiB  
Review
The Hepatitis B Virus Nucleocapsid—Dynamic Compartment for Infectious Virus Production and New Antiviral Target
by Matthias Niklasch, Peter Zimmermann and Michael Nassal
Biomedicines 2021, 9(11), 1577; https://doi.org/10.3390/biomedicines9111577 - 29 Oct 2021
Cited by 35 | Viewed by 7373
Abstract
Hepatitis B virus (HBV) is a small enveloped DNA virus which replicates its tiny 3.2 kb genome by reverse transcription inside an icosahedral nucleocapsid, formed by a single ~180 amino acid capsid, or core, protein (Cp). HBV causes chronic hepatitis B (CHB), a [...] Read more.
Hepatitis B virus (HBV) is a small enveloped DNA virus which replicates its tiny 3.2 kb genome by reverse transcription inside an icosahedral nucleocapsid, formed by a single ~180 amino acid capsid, or core, protein (Cp). HBV causes chronic hepatitis B (CHB), a severe liver disease responsible for nearly a million deaths each year. Most of HBV’s only seven primary gene products are multifunctional. Though less obvious than for the multi-domain polymerase, P protein, this is equally crucial for Cp with its multiple roles in the viral life-cycle. Cp provides a stable genome container during extracellular phases, allows for directed intracellular genome transport and timely release from the capsid, and subsequent assembly of new nucleocapsids around P protein and the pregenomic (pg) RNA, forming a distinct compartment for reverse transcription. These opposing features are enabled by dynamic post-transcriptional modifications of Cp which result in dynamic structural alterations. Their perturbation by capsid assembly modulators (CAMs) is a promising new antiviral concept. CAMs inappropriately accelerate assembly and/or distort the capsid shell. We summarize the functional, biochemical, and structural dynamics of Cp, and discuss the therapeutic potential of CAMs based on clinical data. Presently, CAMs appear as a valuable addition but not a substitute for existing therapies. However, as part of rational combination therapies CAMs may bring the ambitious goal of a cure for CHB closer to reality. Full article
(This article belongs to the Special Issue Conformational Dynamics of Viral Proteins)
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21 pages, 3682 KiB  
Article
Classical and Quantum Gases on a Semiregular Mesh
by Davide De Gregorio and Santi Prestipino
Appl. Sci. 2021, 11(21), 10053; https://doi.org/10.3390/app112110053 - 27 Oct 2021
Cited by 3 | Viewed by 1917
Abstract
The main objective of a statistical mechanical calculation is drawing the phase diagram of a many-body system. In this respect, discrete systems offer the clear advantage over continuum systems of an easier enumeration of microstates, though at the cost of added abstraction. With [...] Read more.
The main objective of a statistical mechanical calculation is drawing the phase diagram of a many-body system. In this respect, discrete systems offer the clear advantage over continuum systems of an easier enumeration of microstates, though at the cost of added abstraction. With this in mind, we examine a system of particles living on the vertices of the (biscribed) pentakis dodecahedron, using different couplings for first and second neighbor particles to induce a competition between icosahedral and dodecahedral orders. After working out the phases of the model at zero temperature, we carry out Metropolis Monte Carlo simulations at finite temperature, highlighting the existence of smooth transitions between distinct “phases”. The sharpest of these crossovers are characterized by hysteretic behavior near zero temperature, which reveals a bottleneck issue for Metropolis dynamics in state space. Next, we introduce the quantum (Bose-Hubbard) counterpart of the previous model and calculate its phase diagram at zero and finite temperatures using the decoupling approximation. We thus uncover, in addition to Mott insulating “solids”, also the existence of supersolid “phases” which progressively shrink as the system is heated up. We argue that a quantum system of the kind described here can be realized with programmable holographic optical tweezers. Full article
(This article belongs to the Special Issue Computer Simulation of Quantum and Classical Systems)
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