Abstract

Microplastics pose a severe threat to marine ecosystems; however, relevant mathematical modeling and analysis are lacking. This paper formulates two stoichiometric producer-grazer models to investigate the interactive effects of microplastics, nutrients, and light on population dynamics under different settings. One model incorporates optimal microplastic uptake and foraging behavior based on nutrient availability for natural settings, while the other model does not include foraging in laboratory settings. We establish the well-posedness of the models and examine their long-term behaviors. Our results reveal that in natural environments, producers and grazers exhibit higher sensitivity to microplastics, and the system may demonstrate bistability or tristability. Moreover, the influences of microplastics, nutrients, and light intensity are highly intertwined. The presence of microplastics amplifies the constraints on grazer growth related to food quality and quantity imposed by extreme light intensities, while elevated phosphorus input enhances the system’s resistance to intense light conditions. Furthermore, higher environmental microplastic levels do not always imply elevated microplastic body burdens in organisms, as organisms are also influenced by nutrients and light. We also find that grazers are more vulnerable to microplastics, compared to producers. If producers can utilize microplastics for growth, the system displays significantly greater resilience to microplastics.

Introduction

Plastic pollution has steadily increased due to widespread plastic use, insufficient disposal practices, and limited waste management capacity over decades. Plastic wastes discharged into terrestrial and aquatic habitats are considered a serious threat to biodiversity, due to their resistance to decomposition (Gall and Thompson, 2015, Carbery et al., 2018). The small plastic particles, ranging from 0.1 to 5 mm in size, are called microplastics (EFSA Panel on Contaminants in the Food Chain (CONTAM), 2016). Microplastics are observed almost in all aquatic habitats (Eerkes-Medrano et al., 2015, Peeken et al., 2018). Chronic exposure to microplastics presents several challenges for aquatic organisms (Cui et al., 2017, Duis and Coors, 2016, Nolte et al., 2017, Zhang et al., 2017, Khoironi et al., 2019, Sjollema et al., 2016, Besseling et al., 2014).

Studies have shown that microplastics can be absorbed, concentrated, and transported into various organisms, such as algae. This process significantly hampers algal growth, chlorophyll levels, and photosynthetic activity (Cao et al., 2022, Liu et al., 2019, Chae et al., 2019, Wu et al., 2021, Jiao et al., 2022, Gray and Weinstein, 2017, Zhang et al., 2017, Sjollema et al., 2016, Yang et al., 2020, Ferguson, 2011, Wang et al., 2020, Khoironi et al., 2019, Rodrigues et al., 2019, Salman et al., 2016). This inhibition may occur due to physical factors, such as the blockage of light and airflow (Bhattacharya et al., 2010, Wang et al., 2020, Salman et al., 2016, Bhattacharya et al., 2010), or interactions between microplastics and algae, including adsorption, aggregation (Zhang et al., 2017), and the destruction of algal cell walls through surface absorption (Liu et al., 2019). However, it is worth noting that some laboratory studies suggest that certain algae species may increase in the presence of smaller-sized microplastics, possibly because microplastic particles can be utilized as substrates for the growth of algae (Yokota et al., 2017, Mao et al., 2018, Jiao et al., 2022, Canniff and Hoang, 2018).

Discussion

Microplastics can be mistakenly ingested or adhere to the surfaces of marine organisms, resulting in significant adverse effects (Zhang et al., 2017, Liu et al., 2019, Sazli et al., 2023, Gregory, 1996, Derraik, 2002, Blarer and Burkhardt-Holm, 2016, Alomar et al., 2017). This paper presents two stoichiometric models to investigate population dynamics in the presence of microplastics in both field and laboratory settings. The interactive effects of light, nutrients, and microplastics on population dynamics have been rigorously studied.

For natural ecosystems, the OMUF model reveals complex dynamics. When the microplastic concentration is relatively low, the behavior of the system is strongly influenced by the initial conditions and can exhibit bistability or tristability. Conversely, when microplastics in the environment become excessively abundant, the only outcome is the extinction of grazers. Furthermore, the tolerance to microplastics of the producer-grazer system described in OMUF model (3.5) is significantly lower, compared to that of the system defined in NM model (2.11). This discrepancy potentially arises from the fact that in the natural ecosystem, grazers have to face more challenges and pay significant feeding costs, such as food scarcity, nutrient deficiencies, predation risk, multiple toxins, and human impact, making them more susceptible to microplastics.

Extreme light condition, either too low or too high, restricts the growth of grazers. When light intensity is excessively low, producers can only survive at low densities due to weakened photosynthesis, and grazers go extinct because of insufficient food. When light intensity is excessively high, the P:C ratio in producers becomes very low, and grazers go extinct due to nutrient deficiency. However, when light intensity falls within a moderate range, coexistence of both species may occur, and the system demonstrates a greater ability to withstand microplastics.

Abstract

1. Introduction

2. Experimental

3. Results and discussion

4. Conclusion

Conflict of Interest

Supplementary Information

References

Abstract

     This study investigates the effect of graphene oxide (GO) on the mechanical and corrosion behavior, antibacterial performance, and cell response of Mg—Zn—Mn (MZM) nanocomposite. MZM/GO nanocomposites with different amounts of GO (i.e., 0.5wt%, 1.0wt%, and 1.5wt%) were fabricated by the semi-powder metallurgy method. The influence of GO on the MZM nanocomposite was analyzed through the hardness, compressive, corrosion, antibacterial, and cytotoxicity tests. The experimental results showed that, with the increase in the amount of GO (0.5wt% and 1.5wt%), the hardness value, compressive strength, and antibacterial performance of the MZM nanocomposite increased, whereas the cell viability and osteogenesis level decreased after the addition of 1.5wt% GO. Moreover, the electrochemical examination results showed that the corrosion behavior of the MZM alloy was significantly enhanced after encapsulation in 0.5wt% GO. In summary, MZM nanocomposites reinforced with GO can be used for implant applications because of their antibacterial performance and mechanical property.

Introduction

     Currently, because magnesium (Mg) alloys have more benefits than common metallic materials, ceramics, and biodegradable polymers, their biomedical applications have been increasing. In terms of mechanical features, metals have higher mechanical strength and fracture toughness than ceramics or polymers; thus, metals are more appropriate for load-bearing usages than ceramics or polymers [1–2]. The density of human cortical bone (1.75 g/cm3 ) is similar to the density of Mg (1.738 g/cm3 ) and Mg alloys (1.75–1.85 g/cm3 ) but lower than the density of biomedical titanium alloy Ti6Al4V (4.47 g/cm3 ) [3–4]. In terms of biocompatibility, certain amounts of Mg ions in the human body are connected with many metabolic reactions and biological mechanisms [5–6]. Mg alloys are suitable orthopedic and cardiovascular implants because further surgery to remove them is not needed [7–8]. However, an important drawback of Mgbased implants is that they do not have good resistance against corrosion in physiological environments [9]. Mechanical strength could be significantly reduced by rapid and uncontrollable corrosion processes, which leads to premature failure [10]. Moreover, the health of patients who have such implants could be at risk because of the evolution of hydrogen gas and alkalinization of the environments close to the interface between implant and tissue [11]. Therefore, to achieve the secure deployment of biomedical devices, the degradation/corrosion rate of Mg alloys needs to be controlled [12]. In this context, several methods, such as alloying, powder metallurgy (PM), and surface modification strategies, have been used in an extensive number of studies that aimed to solve the problem of corrosion in Mg alloys [13–14]. Among the best methods to enhance the corrosion resistance of porous Mg are PM processes, such as mechanical alloying [15–17].

Conclusion

     In this study, using the semi-powder metallurgy method, different contents of GO were embedded in the Mg–Zn–Mn (MZM) matrix to prepare MZM/xGO nanocomposites for orthopedic applications. The corrosion performance and the 24 20 16 12 8 4 0 0 −0.5 −1.0 −1.5 −2.0 Extension / mm MZM/GO Graphene oxide Graphene oxide Graphene oxide Graphene oxide Crack Crack (a) (c) 1.5GO 0.5GO 1GO MZM (b) MZM composite MZM/0.5GO MZM/1GO MZM/1.5GO 49 59 63 64 Compression strength / N 4820 17810 19960 9620 1.12 1.31 1.44 0.72 Force / (10 3 N) Micro hardness, HV Extension / mm Material nanocomposite Fig. 10.    (a) Typical compressive curves and (b) hardness and compressive strength values of the MZM/xGO nanocomposites; (c) schematic diagram of the crack deflection toughening mechanisms of GO in the MZM/xGO nanocomposites. S. Jabbarzare et al., Effect of graphene oxide on the corrosion, mechanical and biological properties of Mg-based … 317 mechanical and biological characteristics of the MZM/xGO nanocomposites were analyzed. The microstructural assessment showed that a uniform distribution was achieved in the MZM/0.5GO and MZM/1GO nanocomposite specimens. However, agglomeration was observed in the MZM/1.5GO nanocomposite specimen. The results showed that the GO content, hardness value, and compressive strength are positively associated. In this context, the MZM/1GO nanocomposite has higher hardness value and compressive strength than the Mg-based nanocomposite without GO. The MZM/ 0.5GO nanocomposite exhibited a nearly comparable corrosion resistance to the MZM/1GO nanocomposite, even though the incorporation of more GO has an unfavorable effect on the Rct value of the MZM matrix. The MTT assay results showed that the MZM/1GO nanocomposite increased the MG63 cell viability and ALP activity, indicating the increasing level of osteogenesis. The results of the analysis of antibacterial activity showed that the MZM/1.5GO nanocomposite had a noticeable effect on antibacterial effectiveness toward bacteria, including Salmonella–Shigella and Klebsiella pneumoniae. In summary, the results indicate the possibility of utilizing the MZM/1GO nanocomposite for implant applications with effective anti-infection characteristics.

Abstract

     Circular economy approaches are commonly depicted by two cycles, where the biological cycle is associated with regeneration in the biosphere and the technical cycle with reuse, refurbishment, and recycling to maintain value and maximize material recovery. This work, instead, presents an alternative vision to the management of carbon-based materials that integrates the two cycles and enables the phasing-out of fossil carbon from the material system. The aim is to investigate the benefits and global potential of a co-recycling system, as an alternative to conventional recycling systems that separate biomass-based materials (e.g., wood, paper) from fossil-based materials (e.g., plastics). Thermochemical recycling technologies enable the conversion of carbon-based waste materials into high-quality synthetic products, promoting circularity and avoiding carbon losses such as carbon emissions and waste accumulation in landfills and nature. Here, the construction and analysis of co-recycling scenarios show how the deployment of thermochemical recycling technologies can decouple the material system from fossil resource extraction. Furthermore, energy use is reduced if pyrolysis and/or gasification are included in the portfolio of recycling technologies. In a decarbonized energy system, deployment of co-recycling can lead to near-zero carbon emissions, while in more carbon-intensive energy systems the choice of thermochemical recycling route is key to limiting carbon emissions.

Introduction

     Carbon-based fuels (mainly fossil fuels but also biomass) account for about 90% of the current global primary energy supply. Carbon is also a building block in a wide range of materials (carbon-based materials; C-materials) used in society. While fossil fuel use is the main cause of anthropogenic greenhouse gas (GHG) emissions, and a transition away from the use of such fuels is essential to limit the global temperature increase to 1.5 °C (IPCC et al., 2018), the production and use of materials such as plastics, cement and steel entail significant GHG emissions (IEA, 2018; Jambeck et al., 2015). The use of biomass-based products can effectively reduce the use of fossil fuels and GHG-intensive materials. There is also scope for substituting existing biobased products with more benign products. For example, cellulose-based textiles can replace cotton which is associated with soil and water depletion, as well as harmful impacts on human health and biodiversity due to excessive use of pesticides and fertilizers (IPCC et al., 2019c; Niinimäki et al., 2020). However, the biomass supply potential is limited by resource constraints (Gerten, 2018) and implications of expanded biomass use for mitigation and other objectives depend on many factors, including soil and climate conditions, biomass type, land management system, scale and pace of deployment, and influence on land use (Calvin et al., 2021). For instance, cropland expansion for energy crop production may cause deforestation, with consequent GHG emissions and negative impacts on biodiversity (IPCC et al., 2019b).

Conclusion

     A co-recycling scenario utilizing advanced thermochemical recycling is proposed and analyzed. The results show that such a scenario can combine natural and synthetic C-materials in the same recycling scheme and that enables to decoupling of the Carbon Material System from the extraction of fossil resources, as well as minimizing waste generation. Advanced thermochemical recycling enables the recovery of any carbon flow (CO2, natural or synthetic, losses, etc.) and the production of high-quality products. A focus on carbon recycling, instead of material recycling, can improve C-materials (wood, paper, plastics, and textiles) resource management, by increasing the resource utilization from 0.7 to 1.1 tC-material/tCRtM, i.e., producing more C-materials than resources used, as well as reducing the CMS losses by half.

Abstract

I. INTRODUCTION

II. EXPERIMENTAL DETAILS

III. RESULTS

IV. DISCUSSION

V. CONCLUSION

REFERENCES

Abstract

     Nanocomposites have been developed as the third-generation insulating materials. This article introduces the crosslinked polyethylene (XLPE) nanocomposite dielectric doped with a small amount of nano-hexagonal boron nitride ( h -BN), which exhibits excellent insulation properties under high dc voltage. The test results show that XLPE/ h -BN nanocomposites possess significant improvements in dc breakdown strength and 0.1 wt% nano h -BN doping can actually increase the dc breakdown strength by 39%. The space charge properties of the XLPE/ h -BN obtained by the pulsed electro-acoustic (PEA) measurements and the direct current integrated charge [DCIC- Q(t) ] measurements show that the positive homocharge injection under dc voltage is obviously suppressed, and the electrical conductivity under relatively high electric field decreases. The thermally stimulated current results show that the nano h -BN doping introduces only deep charge traps (above 1 eV) to the XLPE matrix. The trap energy is deeper than that of the original traps, and this is the main factor leading to the improvement of the dc insulation properties. Besides, the doping of h -BN does not introduce impurities or change the crystallinity of XLPE. This article presents the novel XLPE/ h -BN nanocomposites with excellent dc insulation properties and indicates the large potential of the nano h -BN-doped insulation materials.

Introduction

     NANOCOMPOSITES have excellent dielectric properties and have become the third-generation insulating materials [1]. Nano-doping can improve corona resistance and electrical tree characteristics as well as regulate dielectric properties of the polymer matrix. More importantly, the dc insulation properties can be enhanced to various degrees by inorganic nanoparticle doping, such as the suppression of the charge injection and transportation, as well as the increase of the breakdown strength. With the construction of high-voltage direct current (HVDC) transmission line in a large scale, the power industries have proposed stricter requirements on the dc insulation performance of insulating materials. Therefore,nanocomposite dielectrics may be more suitable for dc insulation systems in the future, and nanocomposite materials with higher insulation performance need to be continuously developed. For example, crosslinked polyethylene (XLPE)- based nanocomposites are expected to be used in the new generation of HVDC cable.

Conclusion

     The XLPE/h-BN nanocomposite with high dc breakdown strength and suppressed charge injection features were introduced in this study. It is useful to reach the conclusions as follows.

     1) XLPE/h-BN nanocomposite samples with loading content ranging from 0.1 to 3 wt% were prepared successfully. The dc Eb of the nanocomposite sample shows at most a 39% increase under 0.1 wt% loading.

     2) The effect of h-BN doping on the charge trap characteristics of XLPE is a significant increase in the density of deep traps, and this is the main cause for the improvement of dc insulation properties.

Abstract

     Concrete is a primary material in infrastructure projects and is a significant contributor to global climate emissions. However, there is a lack of readily available cement and ready-mix concrete inventory data for evaluating the environmental performance of the industries. This study describes the development of cradle-to-gate inventories for U.S. ready-mix concrete and gate-to-gate inventories for portland cement production technologies. These life-cycle inventories provide baselines for the environmental releases associated with concrete that is used for major infrastructure projects. The inventories are incorporated into the publicly available Greenhouse gases, Regulated Emissions, and Energy use in Technologies (GREET) model. The life-cycle inventories are created using facility-level environmental release data from U.S. datasets normalized to activity levels which are based on production capacity and utilization data provided by Portland Cement Association (PCA) and the U.S. Geological Survey Minerals Yearbook. Unit processes for limestone quarrying, sand and gravel quarrying, and wet-mix concrete batch plants are developed on the basis of national total point-source environmental releases and production statistics, coupled with corresponding flows associated with off-road fuel consumption and other non-point-source emissions. Midpoint impact assessment results are normalized to provide insight into their relative significance in the context of U.S.

Introduction

     Concrete is a primary structural material central to the construction projects throughout the world. It is the second most-consumed material in the world, after water (Miller et al., 2018b). Cement is the binder that holds concrete aggregates together, enabling structural performance. Global cement production of about 4.1 billion tonnes year after year since 2013 (IEA, 2021). Of this, 102 million tonnes, or 2.5%, were consumed in the U.S. Concrete can be transported, pumped, and poured to fill frames in a wide range of forms, and once cured, it is rigid and durable, making it ideal for structural elements, especially distributed transportation infrastructure. As a result, concrete is used in a wide range of construction projects. The Portland Cement Association (PCA) reports that in 2015, 30% of the cement use in the U.S. was for transportation infrastructure, 28% for residential buildings, 18% for nonresidential buildings, 13% for public utilities and water/wastewater systems, and 10% for other applications (PCA, 2016).

Conclusions

     This study provides transparent emissions data for infrastructure modeling within the GREET framework, as well as robust inventories for openLCA modeling, available for free download on the Federal LCA Commons. The four primary kiln technologies employed to produce cement are all available, in addition to the U.S. national average blend, enabling specification of blends that may be more regionally appropriate for specific LCA studies. The ready-mix concrete inventory is appropriate for commonly available truck-delivered concrete and is also adaptable for specified cement blends, including adjustments for modeling batch plants that may be set up for larger infrastructure projects. These data enable transparent assessments of concrete applications with complete inventories across a full suite of life-cycle impact categories. Researchers and decision-makers can use GREET or the data on the Federal Commons to assess the impacts associated with major concrete infrastructure projects.

Abstract

     Wastewater from pharmaceutical industries contains different antibiotics and other effluents that directly affect the environment. For the degradation of antibiotics, nanotechnology is an emerging field in research that majorly focuses on molecules and atoms. Nanoparticles are fine micro-particles with more than one dimension from a size of 1–100 nm. The synthesized nanoparticles can directly be used for the process of degradation of antibiotics in wastewater. Titanium dioxide nanoparticles are majorly used among nanoparticles due to their small surface area and particle size. There are various physical, chemical and conventional (biological) methods for synthesizing titanium dioxide nanoparticles. Green synthesis is an environmentally friendly, less expensive and harmless approach, and these methods are much more efficient than any other physical-chemical means. Titanium dioxide nanoparticles are used for different purposes. In food products, these nanoparticles act as photocatalysts and are also used as a coating material in food packaging. Electrochemical biosensors are combined with titanium dioxide nanoparticles for developing nano sheet matrices. Furthermore, this review describes the usage of biological components (plants, microorganisms like fungi and bacteria) to synthesize titanium dioxide nanoparticles. The present review also focuses on applying synthesized titanium dioxide nanoparticles in various drug delivery systems and other bioactivities.

Introduction

     Water is one of the important components of life used in the domestic, industrial, and agricultural sectors. The increase in consumption leads to an increase in the toxicity of pollutants inside water. The concentrations of emerging pollutants like pharmaceutical compounds have increased [1]. Various types of pharmaceutical compounds are observed in the aqueous environment, including antibiotics. These compounds reach the aquatic habitat through hospital effluents, the pharmaceutical industry and human livestock. The consumption of antibiotics has increased, and the concentration increases inside the aquatic environment, leading to the development of antibiotic-resistant bacteria [2,3].

     To remove antibiotics from wastewater, the traditional sewage treatment method is not appropriate and is not much effective in removing the residuals of antibiotics. Nanoparticles can be used as a photocatalyst for the degradation of antibiotics and other organic pollutants [4]. Nanotechnology is defined as synthesizing and developing various nanomaterials by manipulating the matter at the nanoscale [5]. Nanomaterials are a bridge between molecular material and bulk material. They have a size range of 1–100 nm due to their different shapes, sizes, large surface area, and possess high reactivity [6]. This has become an emerging field in science in the last few years due to its wide range of applications [7]. Because of its small size, the effect can be seen in the physical, optical, chemical properties, melting point, and dielectric constant of various nanoparticles [8].

Conclusion

     The interest in green synthesis is due to its advantages of being innocuous to the environment. Different parts of plants are used for synthesis purposes, and their characterization using various techniques helps form TiO2 NPs of varied shapes and sizes. The green synthesis of TiO2 NPs can be used in biomedical, and the delivery of drugs and antibiotics in wastewater of pharmaceutical industries can be degraded using nanoparticles. Because of the less use of precursors, TiO2 is widely used to remove microbes from water surfaces. The nanoparticles inhibit the growth of microbes and are used in wound dressing. Moreover, nanoparticles synthesized using the green routes are more effective than chemical or physical means.

Abstract

     Synthesis and characterization of new polybutadiene-based polyurethane, graphene quantum dot-MnO2 nanoparticles, and relative nanocomposites were set as the aim of current artwork. For this purpose, a one-pot polymerization approach was employed in preparation of polyurethane through the reaction of amine polyol and toluene diisocyanate (TDI) in presence of DBTDL catalyst. Nanocomposites were synthesized using 1 to 3 incorporation percent of graphene quantum dot-MnO2 nanoparticles in polymer matrix. 1H-NMR and FT-IR spectroscopies confirmed successful synthesis of reaction products including graphene quantum dot-MnO2, polyurethane, and nanocomposites. UV-vis and PL spectrophotometry techniques were applied for achieving optical information of samples. Optical properties of nanocomposites were reserved properly with no great quenching. Thermal stabilities, degradation rates, and thermal characteristics of polyurethane and nanocomposites were investigated using TGA/DTG and DSC analysis. Thermal stability showed direct relationship to nanoparticle content, and 3%wt nanocomposite showed improved thermal behaviour in comparison with pure PU. SEM, XRD, and AFM techniques proved successful nanocomposite synthesis with detecting nanoparticle species and fine nanoparticle dispersion with improved topographic and morphologic characteristics making GQD-MnO2 polyurethane nanocomposites a good candidate for using in optical active and thermal stable coatings.

Introduction

     At a time when socioenvironmental problems of polluting industries are the focus of legislators, the general trend is toward the production of new products from recycled materials, especially waste materials. In the case of polybutadiene, because of most usage in tire production in crosslinked form with sulfur or carbon dioxide, it does not seem so reasonable to pay attention on polybutadiene recycling, at least until recognition of successful separation approaches. However, crude polybutadiene itself faced some issues of processability like high molecular weight, high viscosity, low solubility, and high molding that can be solved for usage in wide speared areas with chain modification [1–4].

      Based on a common belief in green chemistry, it is much more beneficial to produce high-performance polymers form existing low-use ones than new starting monomers. With this respect, chemical modification of polybutadiene chain could make possible goals like raising polymer applications, introducing high-performance polymers, and preventing overproduction of new polymers with optimistic perspective to polybutadiene recycling [5, 6].

     Double-bond scission of polybutadiene chain usually occurs through chain oxidation using hydrogen peroxide, metachloroperbenzoic acid, and dimethyl dioxirane. The molecular weight could be engineered by peracid/double-bond unit ratio [7, 8]. Carbonyl functionalized polybutadiene derived from chain cutting down process is an attractive procedure for polyurea and polyurethane synthesis [9, 10].

Conclusion

     At the beginning of this research, graphene quantum dot was successfully prepared by hydrothermal method and coprecipitation approach in order to have GQD-MnO2 nanoparticle synthesis. GQD and GQD-MnO2 nanoparticle accurate synthesis approved by FT-IR spectroscopy, and optical properties of nanoparticles were investigated with UV-vis and PL techniques. In the following, PU-GQD-MnO2 nanocomposite was prepared through an in situ polymerization reaction of synthesized polyol and TDI diisocyanate in presence of different GQD-MnO2 nanoparticle percent. PU-GQD-MnO2 nanocomposite synthesis was confirmed using FT-IR technique. Also, it was resulted from UV-vis and PL analysis that nanocomposites excellently reserved their optical characteristics. Thermal property improvement of nanocomposites was observed using TGA/DTG and DSC methods. Finally, SEM, XRD, and AFM investigations resulted satisfying nanocomposite synthesis, fine nanoparticle distribution, and morphologic and topographic property improvement in nanocomposites in comparison with pure PU.

Highlights

Abstract

Graphical abstract

Keywords

1. Introduction

2. Apparatus

3. Buffer gas cooling considerations

3.1. Buffer gas cell & pumping requirements

3.2. Diffusion and cooling times

3.3. Buffer gas loading of sublimed molecules

4. Spectrometer sensitivity

5. Conclusion

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgements

References

Abstract

High temperatures and associated poor rotational partition functions have hindered the application of high-resolution rotational spectroscopy for detection of molecules desorbing from an ice substrate. Here, an experimental approach is presented which will enable such investigations through incorporation of a buffer gas cooling cell. We discuss design considerations for this apparatus and the expected performance based upon OC34S measurements made with a related spectrometer in a 14.7 K sampled uniform flow. We highlight specific applications of this technique including chiral sensing of molecules generated in an interstellar ice, and the synthesis of exotic species not amenable to generation in the gas-phase.

I. Introduction

Chemistry taking place in ices profoundly impacts atmospheric chemistry and chemistry in astrochemical environments[1,2]. For example, the synthesis of prebiotic amino acids and sugars, as well as the enantiomeric excess observed on Earth may be attributed to chemistry that took place in ice[3,4]. However, current laboratory studies mainly employ mass spectrometric and Fourier-transform infrared spectroscopic detection and do not take advantage of recent tremendous advances of broadband rotational spectroscopy[5,6]. This is largely because of the disadvantage of the rotational partition function associated with molecules desorbing from these ices at typical temperatures from 80-200 K. A means to cool these molecules offers the advantage of rotational spectroscopy for effective probes of chirality, isomer-specificity, complex mixture analysis, and meaningful relative intensities for product branching ratios. There have been, to our knowledge, two reports on the application of millimeter and submillimeter spectroscopy applied to study interstellar ice chemistry. Widicus-Weaver et al. demonstrated the first such experiments in their detection of thermally desorbed H2O, D2O, and CH3OH originating in a solid film created at ~ 12K[7].

Abstract

Graphical abstract

Keywords

Abbreviations

1. Introduction

2. Materials and methods

3. Results

4. Discussion

5. Conclusions

Author contributions

Declaration of Competing Interest

Acknowledgments

Appendix A. Supplementary data

References

Abstract

The immune checkpoint blockade therapy has profoundly revolutionized the field of cancer immunotherapy. However, despite great promise for a variety of cancers, the efficacy of immune checkpoint inhibitors is still low in colorectal cancer (CRC). This is mainly due to the immunosuppressive feature of the tumor microenvironment (TME). Emerging evidence reveals that certain chemotherapeutic drugs induce immunogenic cell death (ICD), demonstrating great potential for remodeling the immunosuppressive TME. In this study, the potential of ginsenoside Rg3 (Rg3) as an ICD inducer against CRC cells was confirmed using in vitro and in vivo experimental approaches. The ICD efficacy of Rg3 could be significantly enhanced by quercetin (QTN) that elicited reactive oxygen species (ROS). To ameliorate in vivo delivery barriers associated with chemotherapeutic drugs, a folate (FA)-targeted polyethylene glycol (PEG)-modified amphiphilic cyclodextrin nanoparticle (NP) was developed for co-encapsulation of Rg3 and QTN. The resultant nanoformulation (CD-PEG-FA.Rg3.QTN) significantly prolonged blood circulation and enhanced tumor targeting in an orthotopic CRC mouse model, resulting in the conversion of immunosuppressive TME. Furthermore, the CD-PEG-FA.Rg3.QTN achieved significantly longer survival of animals in combination with Anti-PD-L1. The study provides a promising strategy for the treatment of CRC.

1. Introduction

As the third leading cause of cancer-related deaths worldwide (e.g., 881,000 deaths estimated in 2018)1, colorectal cancer (CRC, a cancer of the colon or rectum) is an obvious disease burden requiring effective, safe and widely-applicable treatments. Recent research in cancer immunology has led to the development of different immunotherapeutic strategies2, 3, 4. Among these, strategies that exert the blockade of immune checkpoint pathways [e.g., cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed death-ligand 1 (PD-L1)] have achieved favorable outcomes in a range of solid tumors5. However, it has been reported that only a minority of patients (up to 15% of the CRC population), who are identified with mismatch repair (MMR)-deficient CRC, respond positively to immune checkpoint blockade therapy6, while the response rate remains low in MMR-proficient CRC patients7. This failure is strongly attributed to the immunosuppressive feature of the tumor microenvironment (TME)8. Therefore, approaches designed to reprogram the TME may improve the therapeutic efficacy of immune checkpoint inhibitors9, potentially providing therapeutic benefit for the wide spectrum of CRC patients.

Immunogenic cell death (ICD) is characterized as immunogenic apoptosis that activates damage-associated molecular patterns (DAMPs) in dying or dead tumor cells in response to certain stimuli10. DAMPs as danger signals activate dendritic cells (DCs) for the presentation of tumor-associated antigens (TAAs), which subsequently induce T cell-mediated immunological responses against living tumor cells of the same kind10. The concept of ICD has revolutionized the traditional view of chemotherapeutic agents that are considered cytotoxic and poorly immunogenic. For example, chemotherapeutic drugs such as anthracyclines11, oxaliplatin12, bortezomib13 and cardiac glycosides14 have been identified as the putative ICD inducers. Recently, evaluation of chemotherapeutics as potential ICD inducers has gained increasing attention. In addition, ICD is often concomitant with the production of reactive oxygen species (ROS)10, and the efficacy of ICD may be enhanced by ROS-inducing strategies15, 16, 17. Therefore, it is hypothesized that a combination of ICD- and ROS-inducing strategies will mediate the remodeling of immunosuppressive TME and achieve synergistic immunotherapeutic efficacy with immune checkpoint blockade.

Highlights

Abstract

Graphical abstract

Keywords

1. Introduction

2. Experimental

3. Results and discussion

4. Conclusions

Declaration of Competing Interest

Acknowledgement

Declaration of Competing Interest

Data Availability

Appendix A. Supplementary material

References

Abstract

Ring-opening polymerization of benzoxazine monomers is a complex process and various chemical structures including N,O-acetal structures, phenolic Mannich structures and arylamine Mannich structures are formed in polybenzoxazines. To understand the polymerization mechanism, the effects of temperature, time and solvent polarity on the polymerization routes, chemical structures and thermal properties were studied. It was discovered that the N,O-acetal structures and the phenoxy structures can be obtained in a low-polarity solvent like dichloromethane at low temperature (−20 °C) with the aid of PCl5, while the arylamine Mannich structures can be readily generated in polar solvent like N,N-Dimethylformamide at high temperature (>80 °C) in the presence of PCl5. However, the phenolic Mannich structures can be directly formed at high temperature (>180 °C) without any catalysts. Upon prolonging the reaction time or elevating the temperature, the phenoxy structures easily rearranged into the N,O-acetal structures or the arylamine Mannich structures. Further increasing the temperature will cause the arylamine Mannich structures to rearrange into the phenolic Mannich structures and even the phenolic methylene structures. Therefore, both phenoxy structures and N,O-acetal structures showed poor thermal stability; while the arylamine Mannich structures possessed lower initial decomposition temperature but higher char yield compared with the phenolic Mannich structures because of the formation of thermally unstable iminium ions and the anchoring of dangling aniline moieties.

1. Introduction

Polybenzoxazines (PBzs) are formed by the ring-opening polymerization (ROP) of nitrogen and oxygen containing six-membered heterocyclic compounds, 3,4-dihydro-2H-1,3-benzoxazines. They are labeled as a kind of new high-performance thermosetting resins that possess good properties similar to or even higher than phenolic resins and satisfactory processability resembling epoxy resins [1–6]. Polybenzoxazines have aroused high research enthusiasm in academic communities and drawn much attention from industries because of their well-known merits: high strength, high modulus, good thermal stability, flame retardance, good dielectric properties, good dimensional stability, low water uptake, outstanding processability and tremendous design flexibility [7–12]. More recently, polybenzoxaiznes have found many functional applications such as shape memory, self-healing, catalyst support, pollution treatment, super capacitor, CO2 absorption and corrosion prevention [13–19]. Additionally, polybenzoxazines are of great potential in the future application as the fossil resources are decreasing rapidly but the amines and phenols that can be used to synthesize benzoxazine monomers are abundant and reproducible in nature [20–24].

Highlights

Abstract

Graphical abstract

Keywords

1. Introduction

2. Green synthesis of fluoroquinolone derivatives

3. Recent advances in green synthesis of fluoroquinolone derivatives and their role in anti-infective field

4. Applications of fluoroquinolones

5. Conclusion

6. Future aspects

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgements

Abbreviations

References

Abstract

Fluoroquinolones are of pivotal interest for scientists because of their excellent pharmacological and pharmacokinetic profiles. They have a broad spectrum of antimicrobial activity and show several promising features such as, greater bioavailability, admirable tissue penetration and comparatively lower incidence of antagonistic and lethal effects. These have made the compounds highly desirable to combat several infectious diseases. Various synthetic conventions have been established to hasten the fluoroquinolone’s amination rate and to improve yield. Such methods have significant disadvantages including, costly reagents, usage of vast quantities of harmful solvents, excessive heat and sideways reactions. These drawbacks aren’t appropriate in current pharmaceutical market. Hence, it is highly desirable to develop a newer green and more efficient process for fluoroquinolones synthesis. Green chemistry methodology endeavours to achieve sustainability at the molecular level. The field of green chemistry has shown how chemists can design next-generation products and processes to make them more cost-effective while being virtuous for human health and the environment. This graphical review demonstrates the current developments in the synthesis of fluoroquinolones employing the principles of green chemistry by using the novel, recyclable and environmental-friendly catalysts and solvents.

1. Introduction

The growing prevalence of bacterial and fungal resistance to a wide number of anti-microbial mediators in both community and hospital-acquired infections has become a significant and global well-being issue with approximately 15 million deaths per annum, as currently, accessible medicines may no longer be successful for resistant infections as a consequence of pathogenic microbes implementing a range of strategies to solve these problems [1]. This unwanted occurrence encouraged the researchers to focused on the advancement of newer materials from bio renewable and sustainable sources because of great concerns about the environment, waste accumulation and destruction and the inevitable depletion of fossil resources [2]. Green chemistry is a modern area of chemistry that is rapidly emerging. Its growing significance is in making the use of maximum available resources in such a way that the production of chemical waste is negligible or minimal. This is one of the superlative possible replacements for conventional methods of chemical synthesis. Through using the green methodology, we can’t only evade the usage of harmful and noxious chemicals, but also prevent the development of by-products. Therefore, they are flawlessly responsive to combinatorial synthesis automation. Gedye and Giguere, in 1986, first announced that the organic synthesis under microwave irradiation could be performed very quickly [3]. Microwave irradiation technique is another form of heating, based upon the capability of analogues to convert electromagnetic energy into heat. This approach will help to increase the rates of chemical reactions, yields and safer materials [4].

Highlights

Abstract

Keywords

1. Introduction

2. Methodology

3. Results and discussion

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgement

Appendix A. Supplementary data

Disclaimer

Research Data

References

ABSTRACT

We implement oceanic dimethylsulfide (DMS) emissions and its atmospheric chemical reactions into the Community Multiscale Air Quality (CMAQv53) model and perform annual simulations without and with DMS chemistry to quantify its impact on tropospheric composition and air quality over the Northern Hemisphere. DMS chemistry enhances both sulfur dioxide (SO2) and sulfate (SO2− 4 ) over seawater and coastal areas. It enhances annual mean surface SO2 concentration by +46 pptv and SO2− 4 by +0.33 μg/m3 and decreases aerosol nitrate concentration by − 0.07 μg/m3 over seawater compared to the simulation without DMS chemistry. The changes decrease with altitude and are limited to the lower atmosphere. Impacts of DMS chemistry on SO2− 4 are largest in the summer and lowest in the fall due to the seasonality of DMS emissions, atmospheric photochemistry and resultant oxidant levels. Hydroxyl and nitrate radical-initiated pathways oxidize 75% of the DMS while halogeninitiated pathways oxidize 25%. DMS chemistry leads to more acidic particles over seawater by decreasing aerosol pH. Increased SO2− 4 from DMS enhances atmospheric extinction while lower aerosol nitrate reduces the extinction so that the net effect of DMS chemistry on visibility tends to remain unchanged over most of the seawater.

1. Introduction

In the 30+ years since Charlson et al. (1987) hypothesized that biogenically-produced dimethyl sulfide (DMS) from marine phytoplankton participates in a negative climate feedback loop affecting cloud condensation nuclei and cloudiness, the study of DMS from the world’s oceans has been a vigorous area of research. Though the CLAW hypothesis (named after the authors of Charlson et al., 1987) has been criticized as too simplistic (Quinn and Bates, 2011), the resulting knowledge gained about the sources, oceanic concentrations, and emissions of oceanic DMS has enabled chemical transport and earth systems models to realistically simulate its impacts on air quality and climate. DMS in the ocean is produced from the breakdown of dimethylsulfoniopropionate (DMSP) generated from microalgal metabolic processes and exudation/mortality (Stefels et al., 2007). The concentration of DMS in seawater has been sampled extensively, leading to the construction of the Global Surface Seawater DMS Database (http://saga.pmel.noaa.gov/dms) and interpolated estimates of the global concentration distribution (Kettle et al., 1999; Kettle and Andreae, 2000). An updated climatology of oceanic DMS concentrations using over 47,000 measurements was reported by Lana et al. (2011).