Persistent hepatitis C virus infection in vitro: coevolution of virus and host.

The virological and cellular consequences of persistent hepatitis C virus (HCV) infection have been elusive due to the absence of the requisite experimental systems. Here, we report the establishment and the characteristics of persistent in vitro infection of human hepatoma-derived cells by a recently described HCV genotype 2a infectious molecular clone. Persistent in vitro infection was characterized by the selection of viral variants that displayed accelerated expansion kinetics, higher peak titers, and increased buoyant densities. Sequencing analysis revealed the selection of a single adaptive mutation in the HCV E2 envelope protein that was largely responsible for the variant phenotype. In parallel, as the virus became more aggressive, cells that were resistant to infection emerged, displaying escape mechanisms operative at the level of viral entry, HCV RNA replication, or both. Collectively, these results reveal the existence of coevolutionary events during persistent HCV infection that favor survival of both virus and host

Estimating household air pollution exposures and health impacts from space heating in rural China

Exposure to and the related burden of diseases caused by pollution from solid fuel cooking, known as household air pollution (HAP), has been incorporated in the assessment of the Global Burden of Diseases (GBD) project. In contrast, HAP from space heating using solid fuels, prevalent in countries at middle or high altitudes, is less studied and missing from the GBD assessment. China is an ideal example to estimate the bias of exposure and burden of diseases assessment when space heating is neglected, considering its remarkably changing demands for heating from the north to the south and a large solid-fuel-dependent rural population. In this study, based on a meta-analysis of 27 field measurement studies in rural China, we derive the indoor PM2.5 (fine particulate matter with an aerodynamic diameter smaller than 2.5 μm) concentration for both the heating and non-heating seasons. Combining this dataset with time-activity patterns and percentage of households using solid fuels, we assess the population-weighted annual mean exposure to PM2.5 (PWE) and the health impacts associated with HAP in mainland rural China by county for the year 2010. We find that ignoring heating impacts leads to an underestimation in PWE estimates by 38 μg/m3 for the nationwide rural population (16 to 40 as interquartile range) with substantial negative bias in northern provinces. Correspondingly, premature deaths and disability-adjusted life years will be underestimated by approximately 30 × 103 and 60 × 104 in 2010, respectively. Our study poses the need for incorporating heating effects into HAP risk assessments in China as well as globally

Distinguishing Emission-Associated Ambient Air PM2.5 Concentrations and Meteorological Factor-Induced Fluctuations

Although PM2.5 (particulate matter with aerodynamic diameters less than 2.5 μm) in the air originates from emissions, its concentrations are often affected by confounding meteorological effects. Therefore, direct comparisons of PM2.5 concentrations made across two periods, which are commonly used by environmental protection administrations to measure the effectiveness of mitigation efforts, can be misleading. Here, we developed a two-step method to distinguish the significance of emissions and meteorological factors and assess the effectiveness of emission mitigation efforts. We modeled ambient PM2.5 concentrations from 1980 to 2014 based on three conditional scenarios: realistic conditions, fixed emissions, and fixed meteorology. The differences found between the model outputs were analyzed to quantify the relative contributions of emissions and meteorological factors. Emission-related gridded PM2.5 concentrations excluding the meteorological effects were predicted using multivariate regression models, whereas meteorological confounding effects on PM2.5 fluctuations were characterized by probabilistic functions. When the regression models and probabilistic functions were combined, fluctuations in the PM2.5 concentrations induced by emissions and meteorological factors were quantified for all model grid cells and regions. The method was then applied to assess the historical and future trends of PM2.5 concentrations and potential fluctuations on global, national, and city scales. The proposed method may thus be used to assess the effectiveness of mitigation actions

Strong yet Tough Catalyst-Free Transesterification Vitrimer with Excellent Fire-Retardancy, Durability, and Closed-Loop Recyclability

Despite great advances in vitrimer, it remains highly challenging to achieve a property portfolio of excellent mechanical properties, desired durability, and high fire safety. Thus, a catalyst-free, closed-loop recyclable transesterification vitrimer (TPN1.50) with superior mechanical properties, durability, and fire retardancy is developed by introducing a rationally designed tertiary amine/phosphorus-containing reactive oligomer (TPN) into epoxy resin (EP). Because of strong covalent interactions between TPN and EP and its linear oligomer structure, as-prepared TPN1.50 achieves a tensile strength of 86.2 MPa and a toughness of 6.8 MJ m−3, superior to previous vitrimer counterparts. TPN1.50 containing 1.50 wt% phosphorus shows desirable fire retardancy, including a limiting oxygen index of 35.2% and a vertical burning (UL-94) V-0 classification. TPN1.50 features great durability and can maintain its structure integrity in 1 M HCl or NaOH solution for 100 days. This is because the tertiary amines are anchored within the cross-linked network and blocked by rigid P-containing groups, thus effectively suppressing the transesterification. Owing to its good chemical recovery, TPN1.50 can be used as a promising resin for creating recyclable carbon fiber-reinforced polymer composites. This work offers a promising integrated method for creating robust durable fire-safe vitrimers which facilitate the sustainable development of high-performance polymer composites

Bio-derived Schiff base vitrimer with outstanding flame retardancy, toughness, antibacterial, dielectric and recycling properties

Thermosetting resins are widely used in high-tech applications for excellent mechanical robustness and chemical resistance. With increasing attention to the environmental and usage safety issues, it is necessary to develop bio-derived, recyclable, tough, and fire-retardant thermosetting resins. Herein, a high-performance, vanillin-based vitrimer (CIP1.0) was prepared. The CIP1.0 with 1.0 wt% phosphorus passes vertical burning (UL-94) V-0 rating with a limiting oxygen index (LOI) of 27.2 %. The phosphorus-containing and Schiff base groups act synergistically in gas and condensed phases during combustion, endowing CIP1.0 with outstanding fire retardancy. The CIP1.0 shows excellent toughness with high elongation at break of 45.0 % due to the π-π stacking of numerous rigid aromatic groups and appropriate cross-linking density. The highly symmetrical structure and low polarizability of CIP1.0 result in a low dielectric constant. The CIP1.0 exhibits superior antimicrobial properties. The CIP1.0 can be reprocessed by hot-pressing at 140 °C for 10 min. The non-destructive, closed-loop recycling of carbon fibers in the carbon fiber-reinforced CIP1.0 composite can be achieved under mild conditions due to the degradable Schiff base groups of CIP1.0. In this work, a bio-derived, tough, fire-retardant, low dielectric, and antimicrobial vitrimer is prepared to provide a rational strategy for the design of advanced environmentally friendly thermosetting resins

A generalizable reactive blending strategy to construct flame-retardant, mechanically-strong and toughened poly (L-lactic acid) bioplastics

Poly(L-lactic acid) (PLA) is an environmentally-friendly bioplastic with high mechanical strength, but suffers from inherent flammability and poor toughness. Many tougheners have been reported for PLA, but their synthesis usually involves organic solvents, and they tend to dramatically reduce the mechanical strength and cannot settle the flammability matter. Herein, we develop strong, tough, and flame-retardant PLA composites by reactive blending PLA, 6-((double (2-hydroxyethyl) amino) methyl) dibenzo [c, e] [1,2] oxyphosphate acid 6-oxide (DHDP) and diphenylmethane diisocyanate (MDI) and define it PLA/xGH, where x indicates that the molar ratio of -NCO group in MDI to -OH group in PLA and DHDP is 1.0x: 1. This fabrication requires no solvents. PLA/2GH with a -NCO/-OH molar ratio of 1.02: 1 maintains high tensile strength of 63.0 MPa and achieves a 23.4 % increase in impact strength compared to PLA due to the incorporation of rigid polyurethane chain segment. The vertical combustion (UL-94) classification and limiting oxygen index (LOI) of PLA/2GH reaches V-0 and 29.8 %, respectively, because DHDP and MDI function in gas and condensed phases. This study displays a generalizable strategy to create flame-retardant bioplastics with great mechanical performances by the in-situ formation of P/N-containing polyurethane segment within PLA

Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal

Strong self-healing close-loop recyclable vitrimers via complementary dynamic covalent/non-covalent bonding

Epoxy vitrimers represent a new class of high-performance sustainable resins because of their desired mechanical and thermally malleable properties. Unfortunately, existing epoxy vitrimers cannot self-heal at room temperature (R.T.) due to the trade-off between mechanical robustness, recyclability, and the ‘frozen’ state of vitrimer networks at R.T. Herein, a high-performance hyperbranched epoxy vitrimer (DCNC/50PEDA) via curing bis(2,3-epoxypropyl) cyclohex-4-ene-1,2-dicarboxylate (DCNC) with 50 wt% of a phosphorus/silicon-containing polyethyleneimine (PEDA) at R.T., and the key to this design lies in rationally integrating complementary dynamic non-covalent hydrogen-bonding and π-π stacking and covalent β-hydroxy ester bonds into the high-mobility branched units of the DCNC/50PEDA network. This design endows the vitrimer with a room-temperature self-healing efficiency up to 96.0 %, high mechanical strength reaching 36.0 MPa, and desired closed-loop recyclability. Moreover, its strong adhesion to a variety of substrates and exceptional fire retardancy, e.g., a limiting oxygen index of 39.0 % and a desired UL-94 V-0 rating, make it an outstanding fire-retardant coating for flammable substrates, such as wood. Such a performance portfolio enables DCNC/50PEDA to outperform existing self-healing polymer and vitrimers counterparts. This work establishes a promising complementary dynamic design protocol for creating self-healing, strong, recyclable, and fire-safe polymers by integrating dynamic non-covalent interactions and covalent bonds, which hold great real-world applications in industries, such as bulk materials, coatings, and adhesives

A P/N/Si-containing hyperbranched flame retardant for improving mechanical performances, fire safety, and UV resistance of epoxy resins

The applications of epoxy resin (EP) are limited in many high-tech fields due to its unsatisfied fire safety and mechanical properties, but introducing flame retardants usually further deteriorates mechanical properties. In this work, a flame-retardant hyperbranched polymer SD was synthesized from 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), diethanolamine, polyformaldehyde, and phenyltrimethoxysilane (PTMS), and applied in high-performance EP. The results showed that the resultant EP-SD samples maintain high transparency and show improved UV-shielding performances. 1.5 wt% of SD allows EP to achieve a vertical burning UL-94 V-0 classification, indicative of high efficiency. EP-SD6 with 6 wt% SD obtains a limiting oxygen index (LOI) of 36.0 % and its peak heat release rate (PHRR) and peak smoke release rate (PSPR) are 65.4 % and 20.2 % lower than those of the neat EP. The addition of SD also improves the mechanical properties of EP. The tensile strength, elongation at break, flexural strength and impact strength of EP-SD6 are increased by 70.4 %, 68.4 %, 30.2 % and 59.7 %, respectively. The superior flame retardancy and mechanical properties of EP-SD6 enable it to stand out from flame-retardant EP systems. Therefore, this work provides a rational design strategy for preparing fire-safe EPs with great optical and mechanical properties based on hyperbranched polymers, which can satisfy the requirements of different industries

A transparent epoxy vitrimer with outstanding flame retardancy, toughness, and recyclability enabled by a hyperbranched P/N-derived polyester

Despite the tremendous advances in vitrimers, it is still a challenge to realize advanced vitrimers with high transparency, toughness, and fire safety. To achieve this performance portfolio, the closed-loop recyclable transesterification vitrimer (HPN1.80) with excellent transparency, toughness, and flame retardancy was prepared by incorporating a hydroxy-terminated hyperbranched polyester (HPN) into diglycidyl ether of bisphenol-A (DGEBA)/methyl tetrahydrophthalic anhydride (MeTHPA) system. HPN was easily obtained by esterification of triethanolamine (TEOA) and 9,10-dihydro-10-(2,3-dicarboxypropyl)-9-oxa-10-phosphaphenanthrene 10-oxide (DDP). Owing to the favorable compatibility of HPN with the matrix, the resulting HPN1.80 exhibited a high transmittance of 85.9% at 700 nm, a toughness of 2.3 MJ/m3, and an impact strength of 4.5 kJ/m2. The phosphorus-containing groups of HPN played an important role in the gas/condensed flame retardancy, allowing HPN1.80 to pass the vertical burning (UL-94) V-0 classification with a limiting oxygen index (LOI) of 32.6%. Due to the catalysis by hydroxyl and tertiary amines, the broken HPN1.80 can be recycled by hot-pressing at 200 °C for 1 h. The regenerated HPN1.80 achieved an LOI of 31.8% and a UL-94 V-0 rating even after two physical reprocessing cycles. For the carbon fiber-reinforced HPN1.80 (CF/HPN1.80) composites, the non-destructive recycling of carbon fibers (CFs) can be achieved due to the presence of a degradable ester group within HPN1.80. This work offers a rational strategy for creating advanced epoxy vitrimers with recyclability, transparency, toughening, and flame retardancy