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.
Treatment of periodontitis aims at preventing further disease progression with the intentions to reduce the risk of tooth loss, minimize symptoms and perception of the disease, possibly restore lost ...periodontal tissue and provide information on maintaining a healthy periodontium. Therapeutic intervention includes introduction of techniques to change behavior, such as: individually tailored oral‐hygiene instructions; a smoking‐cessation program; dietary adjustment; subgingival instrumentation to remove plaque and calculus; local and systemic pharmacotherapy; and various types of surgery. No single treatment option has shown superiority, and virtually all types of mechanical periodontal treatment benefit from adjunctive antimicrobial chemotherapy. Periodontal treatment, because of the chronic nature of periodontitis, is a lifelong commitment to intricate oral‐hygiene techniques, which, when properly implemented, will minimize the risk of disease initiation and progression.
In trees, the use of nonstructural carbon (NSC) under limiting conditions impacts the age structure of the NSC pools. We compared model predictions of NSC ages and transit times for Pinus halepensis, ...Acer rubrum and Pinus taeda, to understand differences in carbon (C) storage dynamics in species with different leaf phenology and growth environments.
We used two C allocation models from the literature to estimate the NSC age and transit time distributions, to simulate C limitation, and to evaluate the sensitivity of the mean ages to changes in allocation fluxes.
Differences in allocation resulted in different NSC age and transit time distributions. The simulated starvation flattened the NSC age distribution and increased the mean NSC transit time, which can be used to estimate the age of the NSC available and the time it would take to exhaust the reserves. Mean NSC ages and transit times were sensitive to C fluxes in roots and allocation of C from wood storage.
Our results demonstrate how trees with different storage traits are expected to react differently to starvation. They also provide a probabilistic explanation for the ‘last-in, first-out’ pattern of NSC mobilization from well-mixed C pools.
Objectives
Recent scientific evidences suggest a relevant role of the oral cavity in the transmission and pathogenicity of SARS-CoV-2.
Methods
A literature search was performed in PubMed, up to April ...30, 2020, focusing on SARS-CoV-2, COVID-19, oral cavity, and antimicrobial agents.
Results
Oral viral load of SARS-CoV-2 has been associated with the severity of COVID-19, and thus, a reduction in the oral viral load could be associated with a decrease in the severity of the condition. Similarly, a decrease in the oral viral load would diminish the amount of virus expelled and reduce the risk of transmission, since (i) during the first 10 days, the virus mainly accumulates at the nasal, oral, and pharyngeal area; (ii) the number of angiotensin-converting enzyme (ACE2) receptor is greater in the salivary glands as compared with the lungs; and (iii) salivary droplets represent the most relevant transmission route. To reduce the oral viral load, antiseptic agents may be used, although the evidence on its efficacy is indirect and weak.
Conclusions
Antiseptic mouth rinses, such as those containing cetylpyridinium chloride or povidone-iodine, may be able to decrease the severity of COVID-19 by reducing oral viral load in infected subjects and decreasing the risk of transmission by limiting viral load in droplets, generated in normal life, or in aerosols, produced during dental procedures. Well-designed clinical and preclinical research must be conducted to support these hypotheses.
Clinical relevance
Antiseptic mouth rinses may help in decreasing the severity of COVID-19 and in reducing the risk of transmission.
Aim
To answer the following PICOS questions: in patients with periodontitis, which is the efficacy of adjunctive systemic antimicrobials, in comparison with subgingival debridement plus a placebo, in ...terms of probing pocket depth (PPD) reduction, in randomized clinical trials with at least 6 months of follow‐up?
Material and Methods
A systematic search was conducted: 34 articles (28 studies) were included. Data on clinical outcome variables changes were pooled and analysed using weighted mean differences (WMDs), 95% confidence intervals (CI) and prediction intervals (PIs), in case of significant heterogeneity.
Results
For PPD, statistically significant benefits (p < .001) were observed in short‐term studies (WMD = 0.448, 95% CI 0.324; 0.573, PI −0.10 to 0.99) and long‐term studies (WMD = 0.485, 95% CI 0.322; 0.648, PI −0.11 to 1.08). Additionally, statistically significant benefits were also found for clinical attachment level, bleeding on probing, pocket closure and frequency of residual pockets. The best outcomes were observed for the combination of amoxicillin plus metronidazole, followed by metronidazole alone and azithromycin. Adverse events were more frequently reported in groups using systemic antimicrobials.
Conclusions
The adjunctive use of systemic antimicrobials in periodontal therapy results in statistically significant benefits in clinical outcomes, with more frequent adverse events in test groups using systemic antimicrobials.
Summary
Non‐structural carbon (NSC) storage (i.e. starch, soluble sugras and lipids) in tree stems play important roles in metabolism and growth. Their spatial distribution in wood may explain ...species‐specific differences in carbon storage dynamics, growth and survival. However, quantitative information on the spatial distribution of starch and lipids in wood is sparse due to methodological limitations.
Here we assessed differences in wood NSC and lipid storage between tropical tree species with different growth and mortality rates and contrasting functional types. We measured starch and soluble sugars in wood cores up to 4 cm deep into the stem using standard chemical quantification methods and histological slices stained with Lugol's iodine. We also detected neutral lipids using histological slices stained with Oil‐Red‐O.
The histological method allowed us to group individuals into two categories according to their starch storage strategy: fiber‐storing trees and parenchyma‐storing trees. The first group had a bigger starch pool, slower growth and lower mortality rates than the second group. Lipid storage was found in wood parenchyma in five species and was related to low mortality rates.
The quantification of the spatial distribution of starch and lipids in wood improves our understanding of NSC dynamics in trees and reveals additional dimensions of tree growth and survival strategies.
Peri‐implant diseases are defined as inflammatory lesions of the surrounding peri‐implant tissues and include peri‐implant mucositis (an inflammatory lesion limited to the surrounding mucosa of an ...implant) and peri‐implantitis (an inflammatory lesion of the mucosa that affects the supporting bone with resulting loss of osseointegration). This review aims to describe the different approaches to manage both entities and to provide a critical evaluation of the evidence available on their efficacy. Therapy of peri‐implant mucositis and nonsurgical therapy of peri‐implantitis usually involve mechanical debridement of the implant surface using curettes, ultrasonic devices, air‐abrasive devices or lasers, with or without the adjunctive use of local antibiotics or antiseptics. The efficacy of these therapies has been demonstrated for mucositis: controlled clinical trials show an improvement in clinical parameters, especially in bleeding on probing. For peri‐implantitis, the results are limited, especially in terms of probing pocket‐depth reduction. Surgical therapy of peri‐implantitis is indicated when nonsurgical therapy fails to control the inflammatory changes. Selection of the surgical technique should be based on the characteristics of the peri‐implant lesion. In the presence of deep circumferential and intrabony defects, surgical interventions should aim to provide thorough debridement, implant‐surface decontamination and defect reconstruction. In the presence of defects without clear bony walls or with a predominant suprabony component, the aim of the surgical intervention should be the thorough debridement and the repositioning of the marginal mucosa to enable the patient to perform effective oral‐hygiene practices, although this aim may compromise the esthetic result of the implant‐supported restoration.
Thermodynamics of optical Bloch equations Elouard, Cyril; Herrera-Martí, David; Esposito, Massimiliano ...
New journal of physics,
10/2020, Volume:
22, Issue:
10
Journal Article
Peer reviewed
Open access
Optical Bloch equations (OBE) describe the coherent exchange of energy between a quantum bit (qubit) and a quasi-resonant driving field in the presence of a thermal bath. Despite it being an ...ubiquitous process in quantum technologies, a sound thermodynamic analysis is still missing. We hereby provide such an analysis, by deriving the relevant framework from first principles. We start from a complete microscopic description of the qubit-bath system where definitions of heat, work and entropy production are unambiguous. We trace out the bath and coarse-grain the resulting expressions in time, using a methodology similar to the derivation of the dynamical master equation, to derive closed expressions for the first and second law in terms of system properties. Long coarse graining times yield the Floquet Master equation and its already known thermodynamic description. Short coarse-graining times yield instead the OBE and a novel thermodynamic framework which explicitly depends on quantum coherences in the qubit's energy basis which produce quantum signatures in the heat and entropy production flows. This allows us to characterize a genuinely quantum non-equilibrium situation, where the coherences created by the driving field are continuously erased by the bath. Our findings can be readily extended to larger open quantum systems. They carry the seeds for future thermodynamic analyses of quantum gates and the design of quantum engines in the strong coherent driving regime.
Abstract
This article sets up a new formalism to investigate stochastic thermodynamics in the quantum regime, where stochasticity and irreversibility primarily come from quantum measurement. In the ...absence of any bath, we define a purely quantum component to heat exchange, that corresponds to energy fluctuations caused by quantum measurement. Energetic and entropic signatures of measurement-induced irreversibility are then explored for canonical experiments of quantum optics, and the energetic cost of counter-acting decoherence is studied on a simple state-stabilizing protocol. By placing quantum measurement in a central position, our formalism contributes to bridge a gap between experimental quantum optics and quantum thermodynamics, and opens new paths to characterize the energetic features of quantum processing.
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