Methylbenzenes are among the most important organic chemicals today and, among them, p‐xylene deserves particular attention because of its production volume and its application in the manufacture of ...polyethylene terephthalate (PET). There is great interest in producing this commodity chemical more sustainably from biomass sources, particularly driven by manufacturers willing to produce more sustainable synthetic fibres and PET bottles for beverages. A renewable source for p‐xylene would allow achieving this goal with minimal disruption to existing processes for PET production. Despite the fact that recently some routes to renewable p‐xylene have been identified, there is no clear consensus on their feasibility or implications. We have critically reviewed the current state‐of‐the‐art with focus on catalytic routes and possible outlook for commercialisation. Pathways to obtain p‐xylene from a biomass‐derived route include methanol‐to‐aromatics (MTA), ethanol dehydration, ethylene dimerization, furan cycloaddition or catalytic fast pyrolysis and hydrotreating of lignin. Some of the processes identified suggest near‐future possibilities, but also more speculative or longer‐term sources for synthesis of p‐xylene are highlighted.
Alternative to fossil fuel? Despite the interest in industry and academia in the implementation of routes to renewable aromatics, there is a lack of clear and practical knowledge regarding such methods. Often, it is overlooked that alternatives to lignin exist from which aromatics can be derived. In view of this, this Review will not only summarize the scientific state‐of‐the‐art of the synthesis of aromatics from bio‐derived compounds but also provide some assessment of any commercial implementation and industrial support.
Limonene: a versatile chemical of the bioeconomy Ciriminna, Rosaria; Lomeli-Rodriguez, Monica; Demma Carà, Piera ...
Chemical communications (Cambridge, England),
01/2014, Letnik:
5, Številka:
97
Journal Article
Recenzirano
(+)-Limonene is a renewable chemical with numerous and growing applications. Its traditional uses such as flavor, fragrance and green solvent are rapidly expanding to include its utilization as a ...platform chemical, extraction solvent for natural products and an active agent for functionalized products. We anticipate that the expansion in uses for limonene will translate into increasing production and use of this relevant natural product, especially for advanced applications.
Largely increased use of (+)-limonene in the emerging bioeconomy will be twofold: in advanced formulations and as raw material to manufacture valued fine chemicals and high-performance polymers, especially using CO
2
as co-monomer.
Iron copper zeolite (Fe‐Cu‐ZSM‐5) with aqueous hydrogen peroxide is active for the selective oxidation of methane to methanol. Iron is involved in the activation of the carbon–hydrogen bond, while ...copper allows methanol to form as the major product. The catalyst is stable, re‐usable and activates methane giving >90 % methanol selectivity and 10 % conversion in a closed catalytic cycle (see scheme).
Chemical recycling is one of the most promising technologies that could contribute to circular economy targets by providing solutions to plastic waste; however, it is still at an early stage of ...development. In this work, we describe the first light-driven, acid-catalyzed protocol for chemical recycling of polystyrene waste to valuable chemicals under 1 bar of O2. Requiring no photosensitizers and only mild reaction conditions, the protocol is operationally simple and has also been demonstrated in a flow system. Electron paramagnetic resonance (EPR) investigations and density functional theory (DFT) calculations indicate that singlet oxygen is involved as the reactive oxygen species in this degradation process, which abstracts a hydrogen atom from a tertiary C–H bond, leading to hydroperoxidation and subsequent C–C bond cracking events via a radical process. Notably, our study indicates that an adduct of polystyrene and an acid catalyst might be formed in situ, which could act as a photosensitizer to initiate the formation of singlet oxygen. In addition, the oxidized polystyrene polymer may play a role in the production of singlet oxygen under light.
Objective
The aim of this work was to assess through a questionnaire the features of vertiginous episodes, accompanying symptoms, familial history, and migraine precursors in a sample of 252 subjects ...with a diagnosis of definite vestibular migraine.
Background
Migraine is a common neurological disorder characterized by episodic headaches with specific features. About two‐thirds of cases run in families, and patients may refer symptoms occurring in infancy and childhood, defined as episodic syndromes that may be associated with migraine. Migraine is associated with episodic vertigo, called vestibular migraine, whose diagnosis mainly relies on clinical history showing a temporary association of symptoms.
Methods
In this cross‐sectional multicentric study, 252 subjects were recruited in different centers; a senior specialist through a structured questionnaire assessed features of vestibular symptoms and accompanying symptoms.
Results
The age of onset of migraine was 23 years, while onset of vertigo was at 38 years. One hundred and eighty‐four subjects reported internal vertigo (73%), while 63 subjects (25%) reported external vertigo. The duration of vertigo attacks was less than 5 minutes in 58 subjects (23%), between 6 and 60 minutes in 55 (21.8%), between 1 and 4 hours in 29 (11.5%), 5 and 24 hours in 44 (17.5%), up to 3 days in 14 (5.5%), and more than 3 days in seven (2.8%); 14 subjects (5.5%) referred attacks lasting from less than 5 minutes and up to 1 hour, nine (3.6%) referred attacks lasting from less than 5 minutes and up to 1 to 4 hours, six (2.4%) referred attacks lasting from less than 5 minutes and up to 5 to 24 hours, and five (2%) cases referred attacks lasting from less than 5 minutes and up to days. Among accompanying symptoms, patients referred the following usually occurring, in order of frequency: nausea (59.9%), photophobia (44.4%), phonophobia (38.9%), vomiting (17.8%), palpitations (11.5%), tinnitus (10.7%), fullness of the ear (8.7%), and hearing loss (4%). In total, 177 subjects referred a positive family history of migraine (70.2%), while 167 (66.3%) reported a positive family history of vertigo. In the sample, 69% of patients referred at least one of the pediatric precursors, in particular, 42.8% of subjects referred motion sickness. The age of onset of the first headache was lower in the subsample with a familial history of migraine than in the total sample. Among the pediatric precursors, benign paroxysmal vertigo – BPV, benign paroxysmal torticollis, and motion sickness were predictive of a lower age of onset of vertigo in adulthood; cyclic vomiting was predictive for vomiting during vertigo attacks in adults.
Conclusions
Our results may indicate that vestibular symptoms in pediatric patients may act as a predisposing factor to develop vestibular migraine at an earlier age in adulthood.
As a consequence of the COVID-19 pandemic, different measures have been implemented by governments from each affected country. Such measures usually involve restrictions on the movement of citizens, ...and have had a profound effect on usual activities and timetables. As a result of school closures and strict restrictions regarding going outside home, children have been one of the most disadvantaged population groups during the lockdown period. We therefore aimed to investigate potential health risk behaviors amongst isolated pre-school and school-aged children. We retrieved relevant articles from MEDLINE, Web of Science, PsycInfo, and Scopus databases to describe identified health-related behaviors (i.e. screen exposure, environmental influence, physical activity and fitness, sedentariness, sleep patterns, eating habits, psychological response, body composition, and injuries) in relation to social isolation and social deprivation of children without previous illness or conditions. This review depicts the potential health-related behaviors according to related literature, and put the focus on future short and long-term sequels of social isolation. Socio-affective complications and insufficient physical activity are underscored as two of the main concerns, particularly among socio-economic deprived children. Both issues could be effectively addressed with either adequate parental or community guidance.
•Social isolation may worsen several health-related behaviors.•Socioeconomic issues could either exacerbate or mitigate social isolation effects.•Socio-affective complications might be derived from prolonged COVID-19 lockdown.•Insufficient physical activity and too much screen exposure could be among the main consequences of COVID-19 lockdown.
The majority of numerical research on kesterite tandem solar cells has predominantly focused on a two‐terminal (2T) configuration that utilizes an ideal tunnel junction. Herein, the performance of ...kesterite tandem solar cells by introducing a photonic crystal structure (1DPC) as intermediate layer in both three‐terminal (3T) and four‐terminal (4T) configurations is investigated. The photonic crystal (1DPC) is designed by stacking ITO and SiO2 layers with the terminal layer consisting of NiO. Optical properties of the 1DPC are modeled. This innovative approach offers several advantages. 1) The 1DPC selectively reflects lower wavelengths, effectively enhancing the short‐circuit current density (Jsc) of the top subcell, while the solar irradiance spectrum at higher‐wavelength optimum for the subcell is not affected. 2) The 1DPC serves as an intermediate electrode, needed for the 3T or 4T configuration. 3) Replacing the conventional Mo back contact with a NiO layer significantly boosts the open‐circuit voltage (Voc) of the top subcell. The findings demonstrate that these configurations exhibit higher performance compared to previously reported results. Furthermore, the utilization of 3T and 4T configurations, incorporating the 1DPC as an electrical beam splitter, provides an effective and accurate design compared to the 2T configuration using ideal tunnel junctions.
This study explores the performance of kesterite tandem solar cells, focusing on three‐terminal (3T) and four‐terminal (4T) configurations using a photonic crystal (1DPC) as an intermediate layer with double functionality: electrode and beam splitter. The 1DPC selectively enhances Jsc in the top subcell without affecting the optimum solar irradiance incoming on the bottom subcell.
Gold nanoparticles (AuNPs) with unique physicochemical properties have received a great deal of interest in the field of biological, chemical and biomedical implementations. Despite the widespread ...use of AuNPs in chemical and biological sensing, catalysis, imaging and diagnosis, and more recently in therapy, no comprehensive summary has been provided to explain how AuNPs could aid in developing improved sensing and catalysts systems as well as medical settings.
The chemistry of Au-based nanosystems was followed by reviewing different applications of Au nanomaterials in biological and chemical sensing, catalysis, imaging and diagnosis by a number of approaches, and finally synergistic combination therapy of different cancers. Afterwards, the clinical impacts of AuNPs, future application of AuNPs, and opportunities and challenges of AuNPs application were also discussed.
AuNPs show exclusive colloidal stability and are considered as ideal candidates for colorimetric detection, catalysis, imaging, and photothermal transducers, because their physicochemical properties can be tuned by adjusting their structural dimensions achieved by the different manufacturing methods.
This review provides some details about using AuNPs in sensing and catalysis applications as well as promising theranostic nanoplatforms for cancer imaging and diagnosis, and sensitive, non-invasive, and synergistic methods for cancer treatment in an almost comprehensive manner.
•We listed different applications of AuNPs as biological and chemical sensing, catalysis, imaging and diagnosis by various techniques.•Moreover, we tried to cover all aspects of Au nanosystems (AuNPs, AuNRs, AuNC, and Au nanoshells) in cancer therapeutics.•Finally, the clinical impact of AuNPs, future application of AuNPs, and opportunities and challenges of AuNPs application were also discussed.
Over the past twenty years there has been intense interest in the design and understanding of catalysis by gold. More recently, it has been observed that alloying gold with a second metal greatly ...enhances the catalytic efficacy. These supported nanoparticles offer great potential as catalysts for the synthesis of fine chemicals and they are now at the stage where they can contribute to the sustainable development of chemical processes, in particular selective oxidation. A number of factors have contributed to this increased interest; namely, environmental issues promoting the need for more atom efficient processes and the new advances in the synthesis of nanoparticles as well as the characterisation methods available for their study. New catalytic materials obtained by careful control of the morphology of the metal nanoparticles and their use under solvent-free conditions all contribute to the latest developments. Most importantly their use can obviate the need to use stoichiometric oxidants. In this perspective we demonstrate the recent advances in these materials for selective oxidation reactions.
Supported metal nanoparticles offer immense scope as new catalysts for selective oxidation of a broad range of substrates particularly under mild reaction conditions with molecular oxygen.
Coenzyme Q10 (CoQ(10)) or ubiquinone is a well-known component of the mitochondrial respiratory chain. In humans, CoQ(10) deficiency causes a mitochondrial syndrome with an unexplained variability in ...the clinical presentations. To try to understand this heterogeneity in the clinical phenotypes, we have generated a Coq9 Knockin (R239X) mouse model. The lack of a functional Coq9 protein in homozygous Coq9 mutant (Coq9(X/X)) mice causes a severe reduction in the Coq7 protein and, as consequence, a widespread CoQ deficiency and accumulation of demethoxyubiquinone. The deficit in CoQ induces a brain-specific impairment of mitochondrial bioenergetics performance, a reduction in respiratory control ratio, ATP levels and ATP/ADP ratio and specific loss of respiratory complex I. These effects lead to neuronal death and demyelinization with severe vacuolization and astrogliosis in the brain of Coq9(X/X) mice that consequently die between 3 and 6 months of age. These results suggest that the instability of mitochondrial complex I in the brain, as a primary event, triggers the development of mitochondrial encephalomyopathy associated with CoQ deficiency.
PDF
