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This review discusses the developments in CO separation techniques in the last few decades and the gaps in knowledge it leaves, as well as sources of CO, both traditional and emerging, which would benefit from improved CO separation.

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 μ-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.

Selective separation of rare earth elements (REEs) from solutions of mixed heavy and light metals by solid adsorbents is an important challenge in the fields of water treatment and metal recovery. The main challenge is water instability of many adsorbents, specifically metal–organic frameworks (MOFs), and their low selectivity. Grafting particular organophosphorus compounds (OPCs) on the MIL-101(Cr) MOF can provide both stability and selectivity. When the tributyl phosphate (TBP), bis(2-ethylhexyl) hydrogen phosphate (D2EHPA or HDEHP) and bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex®-272) OPCs are grafted and applied to mixed-metal aqueous solutions containing Co2+, Ni2+, Cu2+, Zn2+, Nd3+, Gd3+ and Er3+, MIL-101(Cr) offers high selectivity towards the Nd3+, Gd3+ and Er3+ REEs (with stronger affinity towards Er3+). However, the underlying chemistry is unknown and the factors leading to the selectivity remain poorly understood. To uncover the key molecular-level factors, we performed state-of-the-art computational simulations using a combination of high-level density functional theory (DFT), semi-empirical calculations, and configurational sampling of the metal ion-MOF binding modes in aqueous solutions. Our simulation study reproduced the available experimental results, in addition to determining the contributing intermolecular interactions, uptake modes and the most significant structural features for improving selectivity towards the REEs. Therefore, our most important result is rationalization of the mechanism of REE separation by OPC-grafted MOFs using quantum mechanical and electrostatic principles. The results provide guidelines for synthesis of OPC-grafted MIL-101(Cr) structures with enhanced selectivity and stability. Moreover, an efficient computational framework is proposed to facilitate comprehensive modeling of similar systems.

The indivisible relationship between the human host and its oral microbiome has been shaped throughout the millennia, by facing various changes that have forced the adaptation of oral microorganisms to new environmental conditions. In this constant crosstalk between the human host and its microbiome, a bidirectional relationship has been established. The microorganisms provide the host with functions it cannot perform on its own and at the same time the host provides its microbes with a suitable environment for their growth and development. These host factors can positively affect the microbiome, promoting diversity and balance between different species, resulting in a state of symbiosis and absence of pathology. In contrast, other host factors can negatively influence the composition of the oral microbiome and drive the interaction towards a dysbiotic state, where the balance tilts towards a harmful relationship between the host and its microbiome. The aim of this review is to describe the role host factors play in cultivating and maintaining a healthy oral ecology and discuss mechanisms that can prevent its drift towards dysbiosis.

© Copyright © 2021 Cornejo Ulloa, Krom and van der Veen.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.

The ease with which molecular building blocks can be ordered in metal–organic frameworks is an invaluable asset for many potential applications. In this work, we exploit this inherent order to produce chromatic polarizers based on visible-light linear dichroism via cobalt paddlewheel chromophores.

International audience; 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.

p-Nitroaniline presents the typical motif of a second-order nonlinear optically (NLO) active molecule. However, because of its crystallization in an antiparallel and hence centrosymmetric structure, the NLO activity is lost. In this contribution, the p-nitroaniline motif was built successfully into the MIL-53 metal-organic framework. More precisely, MIL-53 was synthesized with 2-amino-5-nitroterephthalate as organic linker, with Al3+, Ga3+, or In3+ as inorganic cation. The Al and Ga structures are polar, as confirmed by second-harmonic generation microscopy, yielding stable NLO materials. Indeed, they contain a 22-36% surplus of the dipolar 2-amino-5-nitro-terephthalate oriented in a parallel fashion. The indium compound was shown to be less crystalline and centrosymmetric. Ab initio modeling of the second-order NLO response shows that the Al and Ga materials show a response comparable to typical inorganic commercial NLO materials such as KDP. As a hybrid material, capable of low-temperature synthesis and processing and the ultrafast NLO responses associated with organic materials, this material can potentially provide an interesting venue for applications with respect to traditional inorganic NLO materials. ispartof: Journal of Physical Chemistry C vol:121 issue:45 pages:25509-25519 ispartof: location:United States status: published

A modulated synthesis approach based on the chelating properties of oxalic acid (H2C2O4) is presented as a robust and versatile method to achieve highly crystalline Al‐based metal‐organic frameworks. A comparative study on this method and the already established modulation by hydrofluoric acid was conducted using MIL‐53 as test system. The superior performance of oxalic acid modulation in terms of crystallinity and absence of undesired impurities is explained by assessing the coordination modes of the two modulators and the structural features of the product. The validity of our approach was confirmed for a diverse set of Al‐MOFs, namely X‐MIL‐53 (X=OH, CH3O, Br, NO2), CAU‐10, MIL‐69, and Al(OH)ndc (ndc=1,4‐naphtalenedicarboxylate), highlighting the potential benefits of extending the use of this modulator to other coordination materials., The chelation of aluminium ions by oxalic acid enables a versatile modulation action, drastically increasing crystal size without undesired framework modifications.

In this work we present a comprehensive experimental study to determine the contact forces between individual metal oxide nanoparticles in the gas-phase using atomic force microscopy. In addition, we determined the amount of physisorbed water for each type of particle surface. By comparing our results with mathematical models of the interaction forces, we could demonstrate that classical continuum models of van der Waals and capillary forces alone cannot sufficiently describe the experimental findings. Rather, the discrete nature of the molecules has to be considered, which leads to ordering at the interface and the occurrence of solvation forces. We demonstrate that inclusion of solvation forces in the model leads to quantitative agreement with experimental data and that tuning of the molecular order by addition of isopropanol vapor allows us to control the interaction forces between the nanoparticles.

Objective Denaturing Gradient Gel Electrophoresis (DGGE) is suggested to predict caries risk in young children. Such a tool would be valuable in orthodontic patients undergoing treatment with fixed appliances. In this cross-sectional study the applicability of DGGE and conventional microbiology for caries risk assessment in orthodontic patients were assessed. Design Dental plaque was obtained from orthodontic patients immediately prior to bracket removal. Presence of white spot lesions (WSL) was assessed immediately post debracketing. DGGE-patterns and band counts were assessed using varying automated band detection settings and compared to visually detected bands to determine optimum settings. Optimum settings were used to compare band patterns in subjects with or without WSL. Microbiological samples were assessed for total colony forming units (CFU’s) and percentages of aciduric flora, Streptococcus mutans, Lactobacillus spp. and Candida albicans . Results Thirty-seven subjects were included with a mean age of 15.4 yr (SD 1.6 yr; 28 with WSL; 9 without WSL). Depending on settings, DGGE outcomes were different. Optimum minimum profiling absolute to the most intense band of 4% showed no significant difference in band numbers for subjects with or without WSL (p = 0.845). Optimum settings for minimum profiling relative to the most intense band of 15% showed significant lower band numbers for subjects with WSL than those without (p = 0.007). No differences between groups were observed for microbiological parameters. Conclusion The analysis of DGGE-patterns is ambiguous. Software settings significantly affected outcomes. DGGE-patterns and band numbers like CFU counts were not predictive with respect to WSL formation in these orthodontic patients.

Objective. White spot lesions (WSL) are an important side-effect of orthodontic multi-bracket (MB) treatment. Standardized monitoring of such WSL may help in caries management. Materials and methods. In this retrospective study the discriminatory power of caries assessment on routine digital oral photographs was compared to quantitative light-induced fluorescence (QLF) imaging in monitoring WSL development after debonding of orthodontic appliances. Oral and QLF photographs captured directly after debond (T1) and 1 year thereafter (T2) of 51 subjects, treated with full MB orthodontic appliances were used. Oral photographs were assessed by use of The International Caries Detection and Assessment System (ICDAS) at both time points independently and by side-by-side comparison to assess visual transition (VT). QLF photographs were categorized based on integrated fluorescence loss at T1 and T2. Results. At T1 433 and 384 lesions on 918 buccal surfaces were detected using ICDAS and QLF, respectively. For both methods these numbers were reduced at T2. Changes within ICDAS scores were recorded by VT and showed mainly lesion improvement within ICDAS score 2. Conclusion. The oral and QLF photographs both showed regression of WSL after debonding of MB orthodontic appliances. The VT evaluation was found to have higher discriminatory power in comparison to ICDAS.

The inclusion of Ti(IV) in water-stable metal-organic frameworks has been proposed as a strategy for the generation of high surface area heterogeneous photocatalysts, with UiO-66 being a promising candidate. We find that the site of binding of Ti(IV) is at linker defect sites and not incorporated into the inorganic secondary building unit through metal exchange. We also demonstrate the choice of titanium source is critical in the generation of an active hydrogen evolution catalyst, and explain the observed activity using density functional theory calculations, which also enable rational design of future Ti(IV) coordination environments in MOF catalysts

The room temperature growth kinetics of the commonly studied metal-organic framework CuBTC (HKUST-1) is investigated with UV/vis absorption spectroscopy. Contrary to chemical intuition, increased concentrations of the BTC ligand slows down the formation of CuBTC. Based on the time-resolved experimental data, a kinetic model is proposed for CuBTC growth. This model is based on a chemical reaction equation sequence for the production of CuBTC including an overcoordinated, slowly reacting Cu-BTCx species. This growth model excellently captures the temporal CuBTC development over the entire range of concentration conditions.

The aim of this study was to assess the red autofluorescence from bacterial species related to dental caries and periodontitis in the presence of different nutrients in the growth medium. Bacteria were grown anaerobically on tryptic soy agar (TSA) supplemented with nutrients, including magnesium-porphyrins from spinach and iron-porphyrins from heme. The autofluorescence was then assessed at 405 nm excitation. On the TSA without additives, no autofluorescence was observed from any of the species tested. On the TSA containing sheep blood, red autofluorescence was observed only from Parvimonas micra. When the TSA was supplemented with blood, hemin, and vitamin K, red autofluorescence was observed from Actinomyces naeslundii, Bifidobacterium dentium, and Streptococcus mutans. Finally, on the TSA supplemented with spinach extract, red autofluorescence was observed from Aggregatibacter actinomycetemcomitans, A. naeslundii, Enterococcus faecalis, Fusobacterium nucleatum, Lactobacillus salivarius, S. mutans, and Veillonella parvula. We conclude that the bacteria related to dental caries and periodontal disease exhibit red autofluorescence. The autofluorescence characteristics of the tested strains depended on the nutrients present, such as metalloporphyrins, suggesting that the metabolic products of the oral biofilm could be responsible for red autofluorescence.

Red and green autofluorescence have been observed from dental plaque after excitation by blue light. It has been suggested that this red fluorescence is related to caries and the cariogenic potential of dental plaque. Recently, it was suggested that red fluorescence may be related to gingivitis. Little is known about green fluorescence from biofilms. Therefore, we assessed the dynamics of red and green fluorescence in real-time during biofilm formation. In addition, the fluorescence patterns of biofilm formed from saliva of eight different donors are described under simulated gingivitis and caries conditions. Biofilm formation was analysed for 12 hours under flow conditions in a microfluidic BioFlux flow system with high performance microscopy using a camera to allow live cell imaging. For fluorescence images dedicated excitation and emission filters were used. Both green and red fluorescence were linearly related with the total biomass of the biofilms. All biofilms displayed to some extent green and red fluorescence, with higher red and green fluorescence intensities from biofilms grown in the presence of serum (gingivitis simulation) as compared to the sucrose grown biofilms (cariogenic simulation). Remarkably, cocci with long chain lengths, presumably streptococci, were observed in the biofilms. Green and red fluorescence were not found homogeneously distributed within the biofilms: highly fluorescent spots (both green and red) were visible throughout the biomass. An increase in red fluorescence from the in vitro biofilms appeared to be related to the clinical inflammatory response of the respective saliva donors, which was previously assessed during an in vivo period of performing no-oral hygiene. The BioFlux model proved to be a reliable model to assess biofilm fluorescence. With this model, a prediction can be made whether a patient will be prone to the development of gingivitis or caries.

The Behavioral Inhibition Questionnaire-Short Form (BIQ-SF) is a 14-item parent-rating scale for assessing an inhibited, anxiety-prone temperament in preschool children. This study examined the psychometric properties of the BIQ-SF scores in a multi-ethnic community population of Dutch boys and girls aged 2.5-6 years (total N = 2,343, from which various subsamples were derived). Results revealed that the factor structure of the BIQ-SF was as hypothesized: a model with six correlated factors representing children's inhibited behaviors in various social and non-social contexts provided a good fit for the data. The internal consistency of the BIQ-SF was generally satisfactory and scores on the scale were found to be fairly stable over a time period of up to 2 years. Parent-teacher agreement was acceptable, and relations between the BIQ-SF and observations of an inhibited temperament were moderate. Finally, BIQ-SF scores were positively associated with measures of anxiety and internalizing symptoms, whereas no significant links were found with externalizing symptoms. Altogether, these results provide support for the reliability and validity of the BIQ-SF as an economical method for assessing behavioral inhibition and anxiety proneness in young children.

Polar metal–organic frameworks have potential applications as functional non-linear optical, piezoelectric, pyroelectric and ferroelectric materials. Using second harmonic generation microscopy we found that fluoride doping of the microporous iron(III) terephthalate MOF MIL-53(Fe) induces a polar organization in its structure, which was not previously detected with XRD. The polar order is only observed when both fluoride and guest molecules are present, and may be related to a complex interplay between the adsorbates and the framework, leading to a modification of the positioning of fluoride in the inorganic Fe-chains. Combined polarized second harmonic generation microscopy and scanning pyroelectric microscopy show that the polar axis is unidirectional and of the same sense over the whole crystal, extending up to 100 micrometers. This finding shows how MOF materials can be endowed with useful properties by doping MOFs with fluoride. crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Karen Markey (ORCID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: This article is freely available. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (CC BY 3.0) history: Received 26 November 2015; Accepted 18 January 2016; Accepted Manuscript published 18 January 2016; Advance Article published 26 January 2016; Version of Record published 1 March 2016 ispartof: Dalton Transactions vol:45 issue:10 pages:4401-4406 ispartof: location:England status: published

Objectives The aim of this cross-sectional study was to assess the correlation between dental plaque scores determined by the measurement of red autofluorescence or by visualization with a two-tone solution. Clinical photographs were used for this study. Materials and methods Overnight plaque from the anterior teeth of 48 participants was assessed for red fluorescence on photographs (taken with a QLF-camera) using a modified Quigley & Hein (mQH) index. A two-tone disclosing solution was applied. Total disclosed plaque was clinically assessed using the mQH index. In addition, total and blue disclosed plaque was scored on clinical photographs using the mQH index. Results A strong correlation was observed between the total disclosed plaque scored on photographs and the clinical scores (r = 0.70 at site level; r = 0.88 at subject level). The correlation between red fluorescent plaque and total plaque, as assessed on the photographs, was moderate to strong and significant (r = 0.50 at the site level; r = 0.70 at the subject level), with the total plaque scores consistently higher than the red fluorescent plaque scores. The correlation between red fluorescent plaque and blue disclosed plaque was weak to moderate and significant (r = 0.30 at the site level; r = 0.50 at the subject level). Conclusions Plaque, as scored on white-light photographs, corresponds well with clinically assessed plaque. A weak to moderate correlation between red fluorescing plaque and total disclosed plaque or blue disclosed plaque was found. Clinical relevance What at present is considered to be matured dental plaque, which appears blue following the application of a two-tone disclosing solution, is not in agreement with red fluorescent dental plaque assessment.

Background : Some dental plaque fluoresces red. The factors involved in this fluorescence are yet unknown. Objective : The aim of this study was to assess systematically the effect of age, thickness, and cariogenicity on the extent of red fluorescence produced by in vitro microcosm biofilms. Design : The effects of biofilm age and thickness on red fluorescence were tested in a constant depth film fermentor (CDFF) by growing biofilms of variable thicknesses that received a constant supply of defined mucin medium (DMM) and eight pulses of sucrose/day. The influence of cariogenicity on red fluorescence was tested by growing biofilm on dentin disks receiving DMM, supplemented with three or eight pulses of sucrose/day. The biofilms were analyzed at different time points after inoculation, up to 24 days. Emission spectra were measured using a fluorescence spectrophotometer (λ exc 405 nm) and the biofilms were photographed with a fluorescence camera. The composition of the biofilms was assessed using 454-pyrosequecing of the 16S rDNA gene. Results : From day 7 onward, the biofilms emitted increasing intensities of red fluorescence as evidenced by the combined red fluorescence peaks. The red fluorescence intensity correlated with biofilm thickness but not in a linear way. Biofilm fluorescence also correlated with the imposed cariogenicity, evidenced by the induced dentin mineral loss. Increasing the biofilm age or increasing the sucrose pulsing frequency led to a shift in the microbial composition. These shifts in composition were accompanied by an increase in red fluorescence. Conclusions : The current study shows that a thicker, older, or more cariogenic biofilm results in a higher intensity of red fluorescence. Keywords: dental plaque; fluorescence; microbiology; biofilms; microbiota; microcosm (Published: 7 April 2016) Citation: Journal of Oral Microbiology 2016, 8: 30346 - http://dx.doi.org/10.3402/jom.v8.30346

Ferroelectric metal–organic frameworks are emerging as an exciting field of research and have witnessed great progress in the last decade. In this contribution, we briefly discuss ferroelectricity and its means of demonstration. Three mechanisms that lead to ferroelectricity are identified and critically discussed. On the basis of the shortcomings present in the literature, we present a protocol for the study of ferroelectricity in MOF compounds.

© The Royal Society of Chemistry 2015. We describe a nonlinear optical study of gold triangles that exploits a higher order plasmonic resonance. A comprehensive nonlinear optical characterisation was performed both by second harmonic generation (SHG) and two photon fluorescence spectroscopy (2PF). We demonstrate and explain the enhancement of the coherent and incoherent nonlinear optical emission by a higher order multipolar mode of the plasmonic structure. The peculiarities of the mode shape and its influence on intensity and polarisation of the nonlinear signal are experimentally and numerically confirmed. crosscheck: This document is CrossCheck deposited related_data: Supplementary Information copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: The accepted version of this article will be made freely available after a 12 month embargo period history: Received 24 October 2014; Accepted 10 December 2014; Advance Article published 7 January 2015; Version of Record published 5 February 2015 ispartof: Journal of Materials Chemistry C vol:3 issue:7 pages:1576-1581 status: published

BackgroundProviding safety education to parents of young children is important in the prevention of unintentional injuries in or around the home. We developed a Web-based, tailored safety advice module to support face-to-face counseling in the setting of preventive youth health care (E-health4Uth home safety) in order to improve the provision of safety information for parents of young children. ObjectiveThis pilot study evaluated a Web-based, tailored safety advice module (E-health4Uth home safety) and evaluated the use of E-health4Uth home safety to support counseling in routine well-child care visits. MethodsFrom a preventive youth health care center, 312 parents with a child aged 10-31 months were assigned to the E-health4Uth home safety condition or to the care-as-usual condition (provision of a generic safety information leaflet). All parents completed a questionnaire either via the Internet or paper-and-pencil, and parents in the E-health4Uth condition received tailored home safety advice either online or by a print that was mailed to their home. This tailored home safety advice was used to discuss the safety of their home during the next scheduled well-child visit. Parents in the care-as-usual condition received a generic safety information leaflet during the well-child visit. ResultsMean age of the parents was 32.5 years (SD 5.4), 87.8% (274/312) of participants were mothers; mean age of the children was 16.9 months (SD 5.1). In the E-health4Uth condition, 38.4% (61/159) completed the online version of the questionnaire (allowing Web-based tailored safety advice), 61.6% (98/159) preferred to complete the questionnaire via paper (allowing only a hardcopy of the advice to be sent by regular mail). Parents in the E-health4Uth condition evaluated the Web-based, tailored safety advice (n=61) as easy to use (mean 4.5, SD 0.7), pleasant (mean 4.0, SD 0.9), reliable (mean 4.6, SD 0.6), understandable (mean 4.6, SD 0.5), relevant (mean 4.2, SD 0.9), and useful (mean 4.3, SD 0.8). After the well-child visit, no significant differences were found between the E-health4Uth condition and care-as-usual condition with regard to the satisfaction with the information received (n=61, P=.51). Health care professionals (n=43) rated the tailored safety advice as adequate (mean 4.0, SD 0.4) and useful (mean 3.9, SD 0.4). ConclusionsLess than half of the parents accepted the invitation to complete a Web-based questionnaire to receive online tailored safety advice prior to a face-to-face consultation. Despite wide access to the Internet, most parents preferred to complete questionnaires using paper-and-pencil. In the subgroup that completed E-health4Uth home safety online, evaluations of E-health4Uth home safety were positive. However, satisfaction scores with regard to tailored safety advice were not different from those with regard to generic safety information leaflets.

Chemistry of materials 25, 17-26 (2013). doi:10.1021/cm3025445, Published by American Chemical Society, Washington, DC

no abstract available ispartof: Angewandte Chemie (International ed.) vol:46 issue:23 pages:4293-4297 ispartof: location:Germany status: published

A basic understanding of the light-scattering processes that take place inside the dental tissue (either sound or carious) is obtained both with measurements of the photon path-length distribution of light inside such media and with Monte Carlo simulations. Furthermore, the following is investigated: the correlations between different moments of the photon path-length distribution of light inside caries lesions, the fluorescence loss determined with quantitative light-induced fluorescence, and/or the demineralization and depth of caries lesions determined with transversal microradiography. It is concluded that (i) the light paths inside both carious and sound enamel are considerably influenced by the refractive-index contrast at the tooth surface; (ii) contrary to a previous hypothesis, the fluorescence loss is larger in lesions in which the average photon path length is longer; (iii) very good correlations are obtained between the optical characteristics and the physical parameters of lesions when the optical measurements are performed such that there is high refractive contrast at the tooth surface. (C) 2003 Optical Society of America.

The aim of this paper is to report on the demineralization-induced changes in dentin autofluorescence. Confocal laser scanning microscopy (CLSM) images and fluorescence excitation and emission spectra of in vitro demineralized root surfaces and sound controls on the same tooth roots were compared. When observed in CLSM images, demineralized dentin, excited at 488 nm, gave an increased emission at 529 nm compared to sound dentin. The difference in fluorescence decreased deeper into the root, as the sound dentin underneath the lesion was reached. In contrast, when using fluorescence spectrophotometry, excitation around 460 and 488 nm yielded a lower emission around 520 nm for demineralized dentin than for sound dentin, but in a more pronounced peak. From excitation spectra for emission around 520 nm, it could be seen that in demineralized dentin the contribution of excitation between 480 and 520 nm was more important than in sound dentin. The recorded fluorescence in CLSM images was not affected by demineralization-caused changes in scattering and absorption properties, due to the small measurement volume. Thus, the increased fluorescence for demineralized dentin implies an increased quantum yield. In fluorescence spectrophotometry, where the measurement volume is large, changes in scattering and absorption do have an influence on the fluorescence signal. Then, increased absorption by non-fluorescing chromophores and increased re-absorption around the emission wavelength may compensate for the increase in quantum yield and absorption around the excitation wavelength by fluorophores.

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.