Combining Nickel- and Zinc-Porphyrin Sites via Covalent Organic Frameworks for Electrochemical CO2 Reduction.

Covalent organic frameworks (COFs) are ideal platforms to spatially control the integration of multiple molecular motifs throughout a single nanoporous framework. Despite this design flexibility, COFs are typically synthesized using only two monomers. One bears the functional motif for the envisioned application, while the other is used as an inert connecting building block. Integrating more than one functional motif extends the functionality of COFs immensely, which is particularly useful for multistep reactions such as electrochemical reduction of CO2. In this systematic study, we synthesized five Ni(II)- and Zn(II)-porphyrin-based COFs, including two pure component COFs (Ni100 and Zn100) and three mixed Ni/Zn-COFs (Ni75/Zn25, Ni50/Zn50, and Ni25/Zn75). Among these, the Ni50/Zn50-COF exhibited the highest catalytic performance for the electroreduction of CO2 to CO and formate at -0.6 V vs RHE, as was observed in an H-cell. The catalytic performance of the COF catalysts was further extended to a zero-gap membrane electrode assembly (MEA) operation where, utilizing Ni50/Zn50, CH4 was detected along with CO and formate at a high current density of 150 mA cm-2. In contrast, under these conditions predominantly H2 and CO were detected at Ni100 and Zn100 respectively, indicating a clear synergistic effect between the Ni- and Zn-porphyrin units.

Elucidating Structural Disorder in Ultra-Thin Bi-Rich Bismuth Oxyhalide Photocatalysts.

Advancing the field of photocatalysis requires the elucidation of structural properties that underpin the photocatalytic properties of promising materials. The focus of the present study is layered, Bi-rich bismuth oxyhalides, which are widely studied for photocatalytic applications yet poorly structurally understood, due to high levels of disorder, nano-sized domains, and the large number of structurally similar compounds. By connecting insights from multiple scattering techniques, utilizing electron-, X-ray- and neutron probes, the crystal phase of the synthesized materials is allocated as layered Bi24O31X10 (X = Cl, Br), albeit with significant deviation from the reported 3D crystalline model. The materials comprise anisotropic platelet-shaped crystalline domains, exhibiting significant in-plane ordering in two dimensions but disorder and an ultra-thin morphology in the layer stacking direction. Increased synthesis pH tailored larger, more ordered crystalline domains, leading to longer excited state lifetimes determined via femtosecond transient absorption spectroscopy (fs-TAS). Although this likely contributes to improved photocatalytic properties, assessed via the photooxidation of benzylamine, increasing the overall surface area facilitated the most significant improvement in photocatalytic performance. This study, therefore, enabled both phase allocation and a nuanced discussion of the structure-property relationship for complicated, ultra-thin photocatalysts.

ORCA-EFCD consensus report on clinical recommendations for caries diagnosis. Paper III: caries diagnosis at the individual level.

The aim of the present consensus paper was to provide recommendations for clinical practice on the individual etiological and modifying factors to be assessed in the individual diagnosis of caries, and the methods for their assessment, supporting personalized treatment decisions. The executive councils of the European Organisation for Caries Research (ORCA) and the European Federation of Conservative Dentistry (EFCD) nominated ten experts each to join the expert panel. The steering committee formed three work groups which were asked to provide recommendations on 1) caries detection and diagnostic methods, 2) caries activity assessment and 3) forming individualised caries diagnoses. The experts responsible for "individualised caries diagnosis" searched and evaluated the relevant literature, drafted this manuscript and made provisional consensus recommendations. These recommendations were discussed and refined during the structured process in the whole work group. Finally, the agreement for each recommendation was determined using an anonymous eDelphi survey. The threshold for approval of recommendations was determined at 70% agreement. Ten recommendations were approved and agreed by the whole expert panel, covering medical history, caries experience, plaque, diet, fluoride and saliva. While the level of evidence was low, the level of agreement was typically very high, except for one recommendation on salivary flow measurement, where 70% agreed. It is recommended that all aspects of caries lesion progression and activity, recent caries experience, medical conditions and medications, plaque, diet, fluoride and saliva should be synthesized to arrive at an individual diagnosis. The expert panel merged evidence from existing guidelines and scientific literature with practical considerations and provided recommendations for their use in daily dental practice.

Predicting and probing the local temperature rise around plasmonic core-shell nanoparticles to study thermally activated processes.

Ultrafast spectroscopy can be used to study dynamic processes on femtosecond to nanosecond timescales, but is typically used for photoinduced processes. Several materials can induce ultrafast temperature rises upon absorption of femtosecond laser pulses, in principle allowing to study thermally activated processes, such as (catalytic) reactions, phase transitions, and conformational changes. Gold-silica core-shell nanoparticles are particularly interesting for this, as they can be used in a wide range of media and are chemically inert. Here we computationally model the temporal and spatial temperature profiles of gold nanoparticles with and without silica shell in liquid and gas media. Fast rises in temperature within tens of picoseconds are always observed. This is fast enough to study many of the aforementioned processes. We also validate our results experimentally using a poly(urethane-urea) exhibiting a temperature-dependent hydrogen bonding network, which shows local temperatures above 90 ◦C are reached on this timescale. Moreover, this experimentally shows the hydrogen bond breaking in such polymers occurs within tens of picoseconds.

ORCA-EFCD consensus report on clinical recommendations for caries diagnosis. Paper II: caries lesion activity and progression assessment.

INTRODUCTION: This consensus paper provides recommendations for oral health professionals on why and how to assess caries activity and progression with special respect to the site of a lesion. METHODS: An expert panel was nominated by the executive councils of the European Organization for Caries Research (ORCA) and the European Federation of Conservative Dentistry (EFCD). The steering committee built three working groups that were asked to provide recommendations on 1) caries detection and diagnostic methods, 2) caries activity and progression assessment and 3) obtain individualized caries diagnoses. The experts of work group 2 phrased and agreed on provisional general and specific recommendations on caries lesion activity and progression, based on a review of the current literature. These recommendations were then discussed and refined in a consensus workshop followed by an anonymous Delphi survey to determine the agreement on each recommendation. RESULTS: The expert panel agreed on general (n=7) and specific recommendations (n=6). The specific recommendations cover coronal caries on pits and fissures, smooth surfaces, proximal surfaces, as well as root caries and secondary caries/ caries adjacent to restorations and sealants (CARS). 3/13 recommendations yielded perfect agreement. CONCLUSION: The most suitable method for lesion activity assessment is the visual-tactile method. No single clinical characteristic is indicative of lesion activity; instead, lesion activity assessment is based on assessing and weighing several clinical signs. The recall intervals for visual and radiographic examination need to be adjusted to the presence of active caries lesions and recent caries progression rates. Modifications should be based on individual patient characteristics.

ORCA-EFCD consensus report on clinical recommendation for caries diagnosis. Paper I: caries lesion detection and depth assessment.

OBJECTIVES: The aim of the present consensus paper was to provide recommendations for clinical practice considering the use of visual examination, dental radiography and adjunct methods for primary caries detection. MATERIALS AND METHODS: The executive councils of the European Organisation for Caries Research (ORCA) and the European Federation of Conservative Dentistry (EFCD) nominated ten experts each to join the expert panel. The steering committee formed three work groups that were asked to provide recommendations on (1) caries detection and diagnostic methods, (2) caries activity assessment and (3) forming individualised caries diagnoses. The experts responsible for "caries detection and diagnostic methods" searched and evaluated the relevant literature, drafted this manuscript and made provisional consensus recommendations. These recommendations were discussed and refined during the structured process in the whole work group. Finally, the agreement for each recommendation was determined using an anonymous Delphi survey. RESULTS: Recommendations (N = 8) were approved and agreed upon by the whole expert panel: visual examination (N = 3), dental radiography (N = 3) and additional diagnostic methods (N = 2). While the quality of evidence was found to be heterogeneous, all recommendations were agreed upon by the expert panel. CONCLUSION: Visual examination is recommended as the first-choice method for the detection and assessment of caries lesions on accessible surfaces. Intraoral radiography, preferably bitewing, is recommended as an additional method. Adjunct, non-ionising radiation methods might also be useful in certain clinical situations. CLINICAL RELEVANCE: The expert panel merged evidence from the scientific literature with practical considerations and provided recommendations for their use in daily dental practice.

Understanding parental perspectives on young children's oral health (≤ 4 years) growing up in a disadvantaged neighbourhood of Amsterdam, the Netherlands: an exploratory study.

BACKGROUND: Families' understanding towards oral health problems among young children is poorly studied. More insight into parents' experiences, especially of those living in disadvantaged neighbourhoods, is needed to address persistent oral health inequalities. This qualitative study aims to explore parental perspectives on children's oral health (≤ 4 years) and the opportunities they see to improve children's oral health. METHODS: Forty-seven mothers and five fathers with different migration backgrounds from a disadvantaged neighbourhood in Amsterdam, the Netherlands, participated in our study. Semi-structured interviews (n = 27), participant observations (n = 7) and one focus group discussion were conducted. A thematic data analysis was used. RESULTS: Parents describe their daily life with young children as busy, hectic and unpredictable. Parents seem to be most concerned about parenting. Mothers, in particular, feel fully responsible for raising their children and managing daily complexities. While most parents value their children's oral health, they all experience challenges. Parents find it hard to limit daily candy intake and to handle unwilling children during tooth brushing. They feel limited support for these issues from their household, social network and professionals. CONCLUSION: Parental struggles in children's oral health are complex and interrelated as they occur across family, societal, community and professional levels. Given the complex daily reality of families with young children, establishing and maintaining healthy oral health habits seems not at the top of parents' minds. They ask for advice in the upbringing of their children backed up by social support, increased attention to children's oral health within the community and professional assistance. Collaborating with parents as knowledgeable partners might be the first step in acting upon the endeavour to address oral health inequality among young children.

Confined Water Cluster Formation in Water Harvesting by Metal-Organic Frameworks: CAU-10-H versus CAU-10-CH3.

Several metal-organic frameworks (MOFs) excel in harvesting water from the air or as heat pumps as they show a steep increase in water uptake at 10-30 % relative humidity (RH%). A precise understanding of which structural characteristics govern such behavior is lacking. Herein, CAU-10-H and CAU-10-CH3 are studied with H, CH3 corresponding to the functions grafted to the organic linker. CAU-10-H shows a steep water uptake ≈18 RH% of interest for water harvesting, yet the subtle replacement of H by CH3 in the organic linker drastically changes the water adsorption behavior to less steep water uptake at much higher humidity values. The materials' structural deformation and water ordering during adsorption with in situ sum-frequency generation, in situ X-ray diffraction, and molecular simulations are unraveled. In CAU-10-H, an energetically favorable water cluster is formed in the hydrophobic pore, tethered via H-bonds to the framework µï£¿OH groups, while for CAU-10-CH3, such a favorable cluster cannot form. By relating the findings to the features of water adsorption isotherms of a series of MOFs, it is concluded that favorable water adsorption occurs when sites of intermediate hydrophilicity are present in a hydrophobic structure, and the formation of energetically favorable water clusters is possible.

Promoting Photocatalytic Activity of NH2-MIL-125(Ti) for H2 Evolution Reaction through Creation of TiIII- and CoI-Based Proton Reduction Sites.

Titanium-based metal-organic framework, NH2-MIL-125(Ti), has been widely investigated for photocatalytic applications but has low activity in the hydrogen evolution reaction (HER). In this work, we show a one-step low-cost postmodification of NH2-MIL-125(Ti) via impregnation of Co(NO3)2. The resulting Co@NH2-MIL-125(Ti) with embedded single-site CoII species, confirmed by XPS and XAS measurements, shows enhanced activity under visible light exposure. The increased H2 production is likely triggered by the presence of active CoI transient sites detected upon collection of pump-flow-probe XANES spectra. Furthermore, both photocatalysts demonstrated a drastic increase in HER performance after consecutive reuse while maintaining their structural integrity and consistent H2 production. Via thorough characterization, we revealed two mechanisms for the formation of highly active proton reduction sites: nondestructive linker elimination resulting in coordinatively unsaturated Ti sites and restructuring of single CoII sites. Overall, this straightforward manner of confinement of CoII cocatalysts within NH2-MIL-125(Ti) offers a highly stable visible-light-responsive photocatalyst.

The effect of sex steroid hormones on the ecology of in vitro oral biofilms.

Sex steroid hormones (SSH) such as oestrogen, progesterone and testosterone are cholesterol derived molecules that regulate various physiological processes. They are present in both blood and saliva, where they come in contact with oral tissues and oral microorganisms. Several studies have confirmed the effect of these hormones on different periodontal-disease-associated bacteria, using single-species models. Bacteria can metabolize SSH, use them as alternative for vitamin K and also use them to induce the expression of virulence factors. However, it is still unclear what the effects of SSH are on the oral microbiome. In this study, we investigated the effects of four SSH on commensal in vitro oral biofilms. Saliva-derived oral biofilms were grown in Mc Bain medium without serum or menadione using the Amsterdam Active-Attachment model. After initial attachment in absence of SSH, the biofilms were grown in medium containing either oestradiol, oestriol, progesterone or testosterone at a 100-fold physiological concentration. Menadione or ethanol were included as positive control and negative control, respectively. After 12 days with daily medium refreshments, biofilm formation, biofilm red fluorescence and microbial composition were determined. The supernatants were tested for proteolytic activity using the Fluorescence Resonance Energy Transfer Analysis (FRET). No significant differences were found in biofilm formation, red fluorescence or microbial composition in any of the tested groups. Samples grown in presence of progesterone and oestradiol showed proteolytic activity comparable to biofilms supplemented with menadione. In contrast, testosterone and oestriol showed a decreased proteolytic activity compared to biofilms grown in presence of menadione. None of the tested SSH had large effects on the ecology of in vitro oral biofilms, therefore a direct translation of our results into in vivo effects is not possible. Future experiments should include other host factors such as oral tissues, immune cells and combinations of SSH as present in saliva, in order to have a more accurate picture of the phenomena taking place in both males and females.

Competitive and Cooperative CO2-H2O Adsorption through Humidity Control in a Polyimide Covalent Organic Framework.

In order to capture and separate CO2 from the air or flue gas streams through nanoporous adsorbents, the influence of the humidity in these streams has to be taken into account as it hampers the capture process in two main ways: (1) water preferentially binds to CO2 adsorption sites and lowers the overall capacity, and (2) water causes hydrolytic degradation and pore collapse of the porous framework. Here, we have used a water-stable polyimide covalent organic framework (COF) in N2/CO2/H2O breakthrough studies and assessed its performance under varying levels of relative humidity (RH). We discovered that at limited relative humidity, the competitive binding of H2O over CO2 is replaced by cooperative adsorption. For some conditions, the CO2 capacity was significantly higher under humid versus dry conditions (e.g., a 25% capacity increase at 343 K and 10% RH). These results in combination with FT-IR studies on equilibrated COFs at controlled RH values allowed us to assign the effect of cooperative adsorption to CO2 being adsorbed on single-site adsorbed water. Additionally, once water cluster formation sets in, loss of CO2 capacity is inevitable. Finally, the polyimide COF used in this research retained performance after a total exposure time of >75 h and temperatures up to 403 K. This research provides insight in how cooperative CO2-H2O can be achieved and as such provides directions for the development of CO2 physisorbents that can function in humid streams.

Carbon monoxide separation: past, present and future.

Large amounts of carbon monoxide are produced by industrial processes such as biomass gasification and steel manufacturing. The CO present in vent streams is often burnt, this produces a large amount of CO2, e.g., oxidation of CO from metallurgic flue gasses is solely responsible for 2.7% of manmade CO2 emissions. The separation of N2 from CO due to their very similar physical properties is very challenging, meaning that numerous energy-intensive steps are required for CO separation, making the CO separation from many process streams uneconomical in spite of CO being a valuable building block in the production of major chemicals through C1 chemistry and the production of linear hydrocarbons by the Fischer-Tropsch process. The development of suitable processes for the separation of carbon monoxide has both industrial and environmental significance. Especially since CO is a main product of electrocatalytic CO2 reduction, an emerging sustainable technology to enable carbon neutrality. This technology also requires an energy-efficient separation process. Therefore, there is a great need to develop energy efficient CO separation processes adequate for these different process streams. As such the urgency of separating carbon monoxide is gaining greater recognition, with research in the field becoming more and more crucial. This review details the principles on which CO separation is based and provides an overview of currently commercialised CO separation processes and their limitations. Adsorption is identified as a technology with the potential for CO separation with high selectivity and energy efficiency. We review the research efforts, mainly seen in the last decades, in developing new materials for CO separation via ad/bsorption and membrane technology. We have geared our review to both traditional CO sources and emerging CO sources, including CO production from CO2 conversion. To that end, a variety of emerging processes as potential CO2-to-CO technologies are discussed and, specifically, the need for CO capture after electrochemical CO2 reduction is highlighted, which is still underexposed in the available literature. Altogether, we aim to highlight the knowledge gaps that could guide future research to improve CO separation performance for industrial implementation.

Structure-Property Relationship of Piezoelectric Properties in Zeolitic Imidazolate Frameworks: A Computational Study.

Metal-organic frameworks (MOFs) are a class of nanoporous crystalline materials with very high structural tunability. They possess a very low dielectric permittivity εr due to their porosity and hence are favorable for piezoelectric energy harvesting. Even though they have huge potential as piezoelectric materials, a detailed analysis and structure-property relationship of the piezoelectric properties in MOFs are lacking so far. This work focuses on a class of cubic non-centrosymmetric MOFs, namely, zeolitic imidazolate frameworks (ZIFs) to rationalize how the variation of different building blocks of the structure, that is, metal node and linker substituents affect the piezoelectric constants. The piezoelectric tensor for the ZIFs is computed from ab initio theoretical methods. From the calculations, we analyze the different contributions to the final piezoelectric constant d14, namely, the clamped ion (e140) and the internal strain (e14int) contributions and the mechanical properties. For the studied ZIFs, even though e14 (e140 + e14int) is similar for all ZIFs, the resultant piezoelectric coefficient d14 calculated from piezoelectric constant e14 and elastic compliance constant s44 varies significantly among the different structures. It is the largest for CdIF-1 (Cd2+ and -CH3 linker substituent). This is mainly due to the higher elasticity or flexibility of the framework. Interestingly, the magnitude of d14 for CdIF-1 is higher than II-VI inorganic piezoelectrics and of a similar magnitude as the quintessential piezoelectric polymer polyvinylidene fluoride.

Professionals' perspectives on how to address persistent oral health inequality among young children: an exploratory multi-stakeholder analysis in a disadvantaged neighbourhood of Amsterdam, the Netherlands.

BACKGROUND: Oral health promotion interventions have had limited success in reaching families in disadvantaged neighbourhoods resulting in persistent oral health inequality. This qualitative study provides insight into professionals' perspectives on children's poor oral health (≤ 4 years), their perceptions of the roles and responsibilities, and opportunities for child oral health promotion strategies. METHODS: Thirty-Eight professionals from different domains (community, social welfare, general health, dental care, public health, private sector) working in a disadvantaged neighbourhood in Amsterdam, the Netherlands, participated through 24 semi-structured (group) interviews. Transcripts and notes were analysed through thematic analysis. RESULTS: Professionals indicate that unhealthy diet, children's non-compliance, poor parental coping, parental low oral health literacy, parent's negative attitude, family's daily struggles, and insufficient emphasis on childhood caries prevention in dental practices, general healthcare and social welfare organisations, underlie poor oral health. They hold parents most responsible for improving young children's oral health, but recognise that families' vulnerable living circumstances and lack of social support are important barriers. Interestingly, non-dental professionals acknowledge their beneficial role in child oral health promotion, and dental professionals stress the need for more collaboration. CONCLUSION: A broad child-, parental-, and societal-centred educational communication strategy is perceived as promising. Professionals working within and outside the dental sector acknowledge that local and collective action is needed. This involves a better understanding of family's complex daily reality. Furthermore, intensifying child oral health knowledge in dental practices is essential in collaboration with families, general health and social welfare organisations.

Relation between the food environment and oral health-systematic review.

BACKGROUND: There is increasing evidence that the food environment, i.e. the availability, accessibility, price and promotion of foods and beverages, has a significant influence on oral health through food consumption. With this systematic literature review, we systematically summarize the available evidence on relations between the food environment and oral health outcomes in children and adults. METHODS: English-language studies were identified through a systematic literature search, executed by a medical information specialist, on OVID/Medline, Embase, Web of Science and CINAHL. Title and abstract screening, full-text screening and quality assessment [using the Quality Assessment with Diverse Studies (QuADS) tool] were done independently by two authors. RESULTS: Twenty-three studies were included, of which 1 studied the consumer food environment (food labeling), 3 the community food environment (e.g. number of food stores in the community), 5 the organizational food environment (availability of healthy foods and beverages in schools), 2 the information environment (television advertisements) and 13 government and industry policies related to the food environment (e.g. implementation of a sugar-sweetened beverage tax). Almost all studies found that unhealthy food and beverage environments had adverse effects on oral health, and that policies improving the healthiness of food and beverage environments improved-or would improve in case of a modeling study-oral health. CONCLUSIONS: This systematic literature review provides evidence, although of low to moderate quality and available in a low quantity only, that several aspects of the food environment, especially policies affecting the food environment, are associated with oral health outcomes.

The Evaluation of the Effects of Two Probiotic Strains on the Oral Ecosystem: A Randomized Clinical Trial.

Introduction: In the current study, we evaluated the effectiveness of two well-defined probiotic strains, Lactobacillus paracasei LPc-G110 (CCTCC M 2013691) and Lactobacillus plantarum GOS42 (DSM 32131), during an experimental gingivitis challenge. The primary objective was to evaluate clinically the effectiveness of lozenges containing one of the two oral probiotic strains, compared with placebo lozenges, on the gingival bleeding (bleeding on marginal probing; BOMP change) after a two-week experimental gingivitis period. The secondary objectives were to assess the effects of the test products on gingival health (Modified Gingival Index; MGI), dental plaque accumulation and fluorescence, and the dynamics of immunological and microbiological aspects after the wash-in phase, followed by a two-week period refraining from oral hygiene and a two-week wash-out phase. Methods: This single-center challenge intervention study was a triple-blind randomized placebo-controlled clinical trial with three parallel groups. The full study population consisted of 117 healthy 18-55 years old human volunteers. Subjects were instructed to use one lozenge, 3 times daily after each meal, containing either L. plantarum, L. paracasei, or lozenges without probiotics (placebo group). After a 2-week wash-in period, the subjects were requested to refrain from any form of oral hygiene for 2 weeks. Results: There were no differences in the primary outcome (BOMP change) among the groups. However, gingival health (MGI) in individuals from the groups exposed to the test products recovered better from experimental gingivitis than the individuals in the placebo group (p = 0.021, one-way ANOVA). The two test products inhibited pro-inflammatory cytokine IL-1ß production, measured in saliva, during the experimental gingivitis period. Both test strains significantly reduced bacterial DNA in tongue samples and L. paracasei strain showed stronger microbiome-modulating potential than the L. plantarum strain. Conclusions: The two tested lozenges with the L. paracasei or L. plantarum strains did show potential for beneficial effects for the oral health of the host during experimental gingivitis to the oral ecosystem.

Impact of the Coronavirus on Providing Oral Health Care in the Netherlands.

OBJECTIVE: Transmission of SARS-CoV-2 during oral health care is potentially increased compared to regular social activities. Specific amendments to the Dutch national infection control guidelines were promulgated. This study aimed to map the impact of the coronavirus pandemic on providing oral health care during the first wave of the coronavirus pandemic in 2020 in the Netherlands. METHODS: A cross-sectional web-based survey was sent via email to a representative sample of dental hygienists and dentists in the Netherlands. RESULTS: Of the 1700 oral health care practitioners approached, 440 (25.9%) responded to the survey. Patient access to oral health care was severely restricted during the lockdown in the spring of 2020. A total of 1.6% of the oral health care practitioners had laboratory-confirmed COVID-19 during the study period, although this is likely to be an underrepresentation due to limited access to testing at that time. Over half of the participants perceived an increased risk of virus transmission during aerosol-generating treatments in their practices. A large majority (65.0%-87.1%) of the oral health care practitioners followed the COVID-19-specific amendments to the national infection control guidelines. Compared to the pre-pandemic period, additional personal protective equipment and protocols were applied. Factors related with compliance with the additional recommendations were age, employment status, and occupation. CONCLUSIONS: The pandemic had a profound impact on both the accessibility and practice of oral health care. This survey study found that most Dutch oral health care practitioners paid extra attention to hygiene and infection control. Also, a low number of COVID-19 infections detected amongst Dutch oral health care practitioners was reported in the Netherlands. These overall outcomes suggest that safe oral health care can be provided when following the current infection control recommendations.

Sex Steroid Hormones as a Balancing Factor in Oral Host Microbiome Interactions.

Sex steroid hormones (SSH) are cholesterol-derived molecules. They are secreted into saliva and enter the oral cavity, triggering physiological responses from oral tissues, with possible clinical implications, such as gingival inflammation and bleeding. SSH and hormonal changes affect not only oral host cells but also oral microorganisms. Historically, most research has focused on the effect of hormonal changes on specific bacteria and yeasts. Recently a broader effect of SSH on oral microorganisms was suggested. In order to assess the role of SSH in host-microbe interactions in the oral cavity, this review focuses on how and up to what extent SSH can influence the composition and behavior of the oral microbiome. The available literature was reviewed and a comprehensive hypothesis about the role of SSH in host-microbiome interactions is presented. The limited research available indicates that SSH may influence the balance between the host and its microbes in the oral cavity.

Emergence of Coupled Rotor Dynamics in Metal-Organic Frameworks via Tuned Steric Interactions.

The organic components in metal-organic frameworks (MOFs) are unique: they are embedded in a crystalline lattice, yet, as they are separated from each other by tunable free space, a large variety of dynamic behavior can emerge. These rotational dynamics of the organic linkers are especially important due to their influence over properties such as gas adsorption and kinetics of guest release. To fully exploit linker rotation, such as in the form of molecular machines, it is necessary to engineer correlated linker dynamics to achieve their cooperative functional motion. Here, we show that for MIL-53, a topology with closely spaced rotors, the phenylene functionalization allows researchers to tune the rotors' steric environment, shifting linker rotation from completely static to rapid motions at frequencies above 100 MHz. For steric interactions that start to inhibit independent rotor motion, we identify for the first time the emergence of coupled rotation modes in linker dynamics. These findings pave the way for function-specific engineering of gear-like cooperative motion in MOFs.