Fluorescent Light Research Articles

Влияние освещенности на молочную продуктивность крупного рогатого скота

Illumination is an important variable that affects the milk yield. The present 90-day experiment took place on the premises of the Experimental Station Grigoryevskoe, Yaroslavl Region, Russia. The cows received feed and water that complied with veterinary and sanitary standards. The authors developed an SP-3 experimental lighting system of twelve LED lights with a total of 108 W. The uniformity of illumination and color rendering was improved by 30%. The control herd lived in their usual stalls with four fluorescent lights (LSP-2x36) with a total of 288 W. The new lighting system increased the energy saving by 2.6 times while the milk yield in the experimental herd grew by 4.5%.

Analisis Efisiensi pada Lampu Movement Area Guidance Sign (MAGS) di Bandar Udara Internasional I Gusti Ngurah Rai - Bali

The Movement Area Guidance Sign (MAGS) is a sign to provide information to the pilot in directing the movement of the aircraft during take-off, landing and taxiing (the road to the apron) efficiently and safely whose electrical power is supplied by a Constant Current Regulator (CCR). where the supply has a constant current and the network system is installed in series so that each lamp has the same brightness intensity. Bali's I Gusti Ngurah Rai International Airport is equipped with an Airfield Lightning System facility, a visual landing aid, one of which is the Movement Area Guidance Sign (MAGS) or better known as the Taxiway Guidance Sign. The MAGS lights at I Gusti Ngurah Rai International Airport Bali have 2 types of lights used, namely, 33 fluorescent type lights and 6 LED type boxes so that the total number of MAGS lights at the airport is 39 MAGS boxes. This research uses this type of research. qualitatively so that the analysis and calculation results show that LED lights are 57.94% more efficient than fluorescent TL lights at MAGS International Airport I Gusti Ngurah Rai. This is caused by the amount of power used by the lamp. In terms of quality, you may get more bang for your buck than your initial investment in MAGS LED lights. This is because LED lamps have a lifespan 3 times longer than fluorescent lamps and are brighter.

Performance analysis of fluorescent and LED lighting sources

"Artificial lighting is a necessity in the conduct of activities, especially at night. The use of fluorescent and LED lighting sources has led to a decrease in electricity consumption compared to incandescent lighting sources. The paper presents a case study highlighting the voltage and current waveforms in the operation of the analyzed sources. A considerable distortion of the current waveform is found, identifying the need for measures to improve power quality. The photometric measurements showed that for some light sources the luminous flux on the box is higher than the luminous flux actually emitted. Keywords: lighting sources, electrical and photometric measurements, waveforms, efficiency"

Digital Restoration of Volatilized⋅Faded Documents

Digital restoration of documents refers to the way for restoring images of records whose legibility is poor due to volatilization⋅fading. The study analyzed the application of VSC(Video Spectral Comparator) to 1,206 sheets of special paper by the National Archives of Korea and digital restoration data. The findings show that most of thermal paper especially the legibility was improved under the ultraviolet condition. Records of sensitive paper, or diazo copying paper, became clear under the conditions of infrared fluorescence light. However, there was no effect for some missing letters so it is regarded that the effects are limited when the initial state of a record is poor. there was insignificant effect for wet copying paper despite application of various light sources. On the other hand, When compared with thermal paper, legibility of documents produced by the Japanese Government-General of Korea in the early 1900s mixed with bast fibers such as tissue paper was improved under various conditions such as visible and infrared rays though it was most visible under the ultraviolet condition. As mentioned above, few number of data makes it difficult to decide a light source adequate for material. However, it was possible to identify the tendency of light sources reacting to material.

Multi-Dimensional Light-Emitting Meta-Display: Photoluminescence and Pumping Light Multiplexing.

The advent of intelligent display devices has given rise to diverse and complex demands for miniature light-emitting devices. Light-emitting metasurfaces have emerged as a practical and efficient means of achieving precise light modulation. However, their practicality is limited by certain constraints. First, there is a need for further exploration of the ability to manipulate both pumping and emitting light simultaneously. Second, there is currently no encoding freedom in multi-dimensional emitting light. To address these concerns, using meta-atoms is proposed to encode both fluorescence and pumping light independently, and expand the encoding freedom with different incident wavevector directions. A light-emitting metasurface with quad-fold multiplex encoding meta-displays, including dual scattering images and dual fluorescence images, is further demonstrated. This design strategy not only manipulates both pumping and fluorescence light but also broadens encoding freedom for comprehensive multi-functionality. This can pave the way for multiplexing optical displays, information storage, and next-generation wearable displays.

Fabrication of silicon quantum dots-methyl viologen nanohybrids: Turn-On-Off-On fluorescence nanoprobe for the detection of d-penicillamine

This study provides a straightforward, one-step hydrothermal approach for synthesizing water-soluble silicon quantum dots (SiQDs). The surface of the synthesized SiQDs is modified by the carboxylic acid functional group (A:SiQDs) after succinic anhydride treatment. The modified A:SiQDs, which emitted blue light fluorescence, showed high stability against photobleaching, thermal stability, and good water solubility. The A:SiQDs are conjugated with methyl viologen (MV2+) to develop a nanohybrid for specific D-Penicillamine (D-PA) detection with an LOD of 8 nM. The suggested sensor was effectively used to analyze D-PA in commercial pharmaceutical formulations using the conventional addition method, and it produced results with good accuracy and precision that were nearly equal to those measured.

Application of Petrographic and Stereological Analyses to Describe the Pore Space of Rocks as a Standard for the Characterization of Pores in Slags and Ashes Generated after the Combustion of Municipal Waste.

Slags and ashes generated in thermal waste treatment facilities require proper management. In line with the principles of the circular economy, new, more economical, and ecological possibilities for utilizing these substances are sought. These waste materials exhibit characteristics similar to rocks in many aspects. This study focuses on analyzing the similarities and differences between nine selected rocks and three samples of slags and ashes obtained from municipal waste incineration. The main research device used was a polarizing microscope, using reflected, transmitted, and fluorescent light. Additionally, low-pressure gas adsorption equipment, as well as helium and quasi-liquid pycnometers, were used for complementary analysis. The parameters analyzed mainly covered broadly defined petrographic properties of rocks and slags, with a particular emphasis on porosity, porous structure, and the spatial distribution of pores and fractures. The conducted analyses confirmed a significant similarity between slags and ashes and clastic sedimentary rocks such as sandstones and mudstones. The research results underscore the importance of petrographic microscopic studies for analyzing materials other than rocks. They also allow for exploring applications for slags and ashes in areas traditionally reserved for natural rock resources. The findings also indicate the necessity of using methods other than microscopic ones to describe the pore space of rocks. The lower measurement range of the optical microscope is limited to approximately 1 μm, covering only macropores. Other methods extend this characteristic to micro- and mesopores. Therefore, a combination of different methods is often employed to obtain a more comprehensive characterization of rock porosity.

Evaluation of the photocatalytic degradation mechanism of methylene blue using nascent and Ag+ ions-modified TiO2.

In photocatalytic removal of organic pollutants, adsorption and degradation are two important processes that take place. Various instrumental techniques and trapping experiments have been used to identify the reactive species and the mechanism of photodegradation. The present work focuses on investigating the mechanism of photo-induced degradation from the comparative characterization of fresh and used samples, isotherm models, competitive adsorption, and desorption studies of pure and Ag+-modified TiO2 NPs. The comparative characterizations of fresh and used NPs were carried out with FT-IR, EDX, and XRF analyses after methylene blue (MB) degradation. The Ag+ doped TiO2 used in this study was fabricated using simple impregnation technique. The prepared NPs were characterized using techniques including XPS, XRD, SEM/EDX, XRF, UV-DRS, and pH point-zero charge analyses (pHPZC). The Ag+-modified TiO2 NPs showed improved efficiency compared to pure TiO2 NPs using normal compact fluorescent light (CFL). The Langmuir and Freundlich isotherm models were applied to test the adsorption behavior on the surface photocatalysts. The investigational data finest fitted to the Langmuir isotherms model compared to Freundlich model, suggesting the homogeneous monolayer adsorption followed by degradations. The competitive removal of MB in the presence of a photo-generated electrons trapper (Cd2+) was enhanced almost 3-folds (115mg/L) compared to the removal from a single MB solution (40mg/L). The characterization of the used samples as well as adsorption in the dark and negligible desorption of used samples support the involvement of the proposed photo-induced degradation mechanism.

Exploring the fluorescence action spectrum of photosynthesis

The mathematical study of the fluorescence action spectrum of photosynthesis was performed. The calculation of typical spectra for photosynthesis was done for the red and blue frequencies. The transition of the action spectrum of photosynthesis from wavelengths to the frequency scale was completed. A numerical method based on the use of the inverse Fourier transform approach was used to obtain a relaxation curve for the impulse (time) characteristic of fluorescence. It turned out that the radius vector of the module of impulse response in polar coordinates makes one half-turn or half of the period of light oscillations in time. It was established that the optical medium of a plant during the relaxation time has a negative space charge of electrons, inverse properties and properties of the coherent radiation. The condition of neutrality of the material environment is not met. It was found that the ratio of the variable chlorophyll fluorescence for red and blue light has almost the same value. An analysis of the dependence of the quality factor of the chlorophyll spectrum on frequency shows that the fluorescence energy loss in blue light significantly exceeds the energy loss in red light. The proposed method can be used for express analysis of the intensity of photosynthesis. It was also concluded that plants can emit ultra-wideband signals. The relaxation time of chlorophyll fluorescence is shorter than the relaxation time of electronic polarization in atoms (molecules). As a result, a population inversion is created in the optical medium of chlorophyll - there are more atoms in the upper energy level than in the lower level. Due to this, stimulated emission and amplification of light of the radiative recombination occur. In this case, the emission of fluorescence light becomes coherent. All these properties of plants are considered for the first time and have not been described either in domestic or in foreign articles.

Use of Silicon Photomultipliers in the Detectors of the JEM-EUSO Program

The JEM-EUSO program aims to study ultra-high energy cosmic rays from space. To achieve this goal, it has realized a series of experiments installed on the ground (EUSO-TA), various on stratospheric balloons (with the most recent one EUSO-SPB2), and inside the International Space Station (Mini-EUSO), in light of future missions such as K-EUSO and POEMMA. At nighttime, these instruments aim to monitor the Earth’s atmosphere measuring fluorescence and Cherenkov light produced by extensive air showers generated both by very high-energy cosmic rays from outside the atmosphere and by neutrino decays. As the two light components differ in duration (order of microseconds for fluorescence light and a few nanoseconds for Cherenkov light) they each require specialized sensors and acquisition electronics. So far, the sensors used for the fluorescence camera are the Multi-Anode Photomultiplier Tubes (MAPMTs), while for the Cherenkov one, new systems based on Silicon PhotoMultipliers (SiPMs) have been developed. In this contribution, a brief review of the experiments is followed by a discussion of the tests performed on the optical sensors. Particular attention is paid to the development, test, and calibration conducted on SiPMs, also in view to optimize the geometry, mass, and weight in light of the installation of mass-critical applications such as balloon- and space-borne instrumentation.

Functional graphitic carbon nitride/hydroxyapatite heterojunction for robust formaldehyde removal at ambient temperature

Ambient-temperature catalytic removal of formaldehyde (HCHO) hazard has been currently reckoned as a practicable and promising approach for abating indoor HCHO which severely haunts the human’s health. Catalyst with high-effectiveness and low-cost is a pivotal parameter determining the reliability and availability of this strategy. Herein, bifunctional graphitic carbon nitride/hydroxyapatite heterostructures (g-C3N4/HAP) were developed for indoor HCHO removal at ambient temperature. The optimal catalyst (g-C3N4/HAP-20) displayed enhanced HCHO removal efficiency of 36.6% and conversion (into CO2) efficiency of 28.4% within 2 h, compared with g-C3N4 (18.0% and 24.0%) and HAP (36.2% and ∼ 0%). Indoor fluorescent light accelerated HCHO elimination and its subsequent decomposition into CO2 over g-C3N4/HAP-20, delivering a HCHO removal efficiency of 82.7% and conversion efficiency of 100% within 2 h. Various characterizations and theoretical calculation reveal that g-C3N4/HAP possessed superoxide radicals and unpair electrons which were responsible for HCHO removal at ambient temperature; and a S-scheme heterostructure remarkably benefited the charge transfer and the photogenerated carriers’ separation, and consequently upgraded HCHO catalytic oxidation under indoor fluorescent-light illumination. This work offers a potent way to construct noble-metal free advanced catalysts with multi-functionality for indoor pollutant purification.

Highly sensitive fluorescent triarylimidazole derivatives for sensing of 2,4,6-trinitrophenol in aqueous solution and its application for actual environment detection

Two highly sensitive fluorescent triarylimidazole derivatives were synthesized by modifying imidazole with coumarin and large conjugate rigid plane structure. XM-F and XM-L emitted bright yellow-green fluorescent light. Their intense conjugation system generated strong π-π electrostatic interactions with TNP, accompanied by the formation of hydrogen bonds to achieve rapid detection of TNP within 25 s. The detection limits were as low as 0.049 μM and 0.071 μM, respectively. Probes had been successfully applied to rapid detection of TNP in real water samples and manufactured into portable fluorescent test strips. In view of excellent performance of XM-F, it was used to achieve real-time, portable, on-site quantitative detection of TNP by a colorimeter and a smartphone platform. In addition, XM-F also successfully processed into probe-coated TLC plates for efficient detection of fingerprints contaminated with TNP.

Long wavelength light exposure reduces systemic inflammation coagulopathy and acute organ injury following multiple injuries in mice.

Evidence suggests that variation in light exposure strongly influences the dynamic of inflammation, coagulation, and the immune system. Multiple injuries induce systemic inflammation that can lead to end-organ injury. Here, we hypothesize that alterations in light exposure influence posttrauma inflammation, coagulopathy, and end-organ injury. C57BL/6 mice underwent a validated multiple-injury and hemorrhage model performed following 72 hours of exposure to red (617 nm, 1,700 lux), blue (321 nm, 1,700 lux), and fluorescent white light (300 lux) (n = 6-8/group). The animals were sacrificed at 6 hours posttrauma. Plasma samples were evaluated and compared for proinflammatory cytokine expression levels, coagulation parameters, markers of liver and renal injury, and histological changes (Carstairs staining). One-way analysis of variance statistical tests were applied to compare study groups. Preexposure to long-wavelength red light significantly reduced the inflammatory response at 6 hours after multiple injuries compared with blue and ambient light, as evidenced by decreased levels of interleukin 6, monocyte chemoattractant protein-1 (both p < 0.001), liver injury markers (alanine transaminase, p < 0.05), and kidney injury markers (cystatin C, p < 0.01). In addition, Carstairs staining of organ tissues revealed milder histological changes in the red light-exposed group, indicating reduced end-organ damage. Furthermore, prothrombin time was significantly lower ( p < 0.001), and fibrinogen levels were better maintained ( p < 0.01) in the red light-exposed mice compared with those exposed to blue and ambient light. Prophylactic light exposure can be optimized to reduce systemic inflammation and coagulopathy and minimize acute organ injury following multiple injuries. Understanding the mechanisms by which light exposure attenuates inflammation may provide a novel strategy to reducing trauma-related morbidity.

Light Sheet-Based Laser Patterning Bioprinting Produces Long-Term Viable Full-Thickness Skin Constructs.

Tissue engineering holds great promise for biomedical research and healthcare, offering alternatives to animal models and enabling tissue regeneration and organ transplantation. 3D bioprinting stands out for its design flexibility and reproducibility. Here, an integrated fluorescent light sheet bioprinting and imaging system is presented that combines high printing speed (0.66 mm3 /s) and resolution (9µm) with light sheet-based imaging. This approach employs direct laser patterning and a static light sheet for confined voxel crosslinking in photocrosslinkable materials. The developed bioprinter enables real-time monitoring of hydrogel crosslinking using fluorescent recovery after photobleaching (FRAP) and brightfield imaging as well as in situ light sheet imaging of cells. Human fibroblasts encapsulated in a thiol-ene click chemistry-based hydrogel exhibited high viability (83% ± 4.34%) and functionality. Furthermore, full-thickness skin constructs displayed characteristics of both epidermal and dermal layers and remained viable for 41 days. The integrated approach demonstrates the capabilities of light sheet bioprinting, offering high speed, resolution, and real-time characterization. Future enhancements involving solid-state laser scanning devices such as acousto-optic deflectors and modulators will further enhance resolution and speed, opening new opportunities in light-based bioprinting and advancing tissue engineering.

Fabrication and characterization of modified POD membranes with ultra-high tensile strength through hydrogen bonding functioning and copolymerization

A series of modified aromatic oxadiazole polymers were synthesized via condensation reactions of terephthalic dihydrazide (TPH) and varying amounts of Trimesic acid (H3BTC) in polyphosphoric acid (PPA). Pentaerythritol was introduced to construct intermolecular hydrogen bonds among polymeric chains, resulting in a three-dimensional network structure, and correlations between H-bonds and mechanic properties are discussed. Structures and mechanic properties of the polymers were characterized and analyzed. By investigation of molecular structure and membrane formation process of chemically modified and hydrogen bond-regulated polymer membranes, it was found that the modified polymer membranes retain the unique thermal stability, chemical stability, and good hydrophobicity of the POD rigid polymer. Additionally, hydrogen bonds not only significantly improve the overall quality of the membrane, but also play an important role in enhancing the mechanical properties of the membrane, as demonstrated in the highest observed of up to a maximum of 167.19 MPa. Furthermore, impact of H3BCT modification on light absorption and fluorescence performance of T-PODx is also analyzed and discussed in this paper.

Potential application of light emitting diodes to improve molecular, physiological, and growth responses in peppermint plant

AbstractBackgroundClimate change and growing global population are driving forces that shift the agriculture from open fields to environmentally‐controlled confined systems. In such confined systems, plants are adapted to unique light spectra to achieve maximal qualitative and quantitative yields. In the present study, effects of five light spectra on morpho‐physiological and molecular attributes of peppermint were examined. Treatments included a traditional greenhouse considered as the control, a fluorescent light, and four types of light emitting diodes (LED): red, blue, red‐blue (70:30), and white. Leaf samples were collected from plants and analyzed for volatile constituents using a headspace GC–MS. Meanwhile, changes in the expression profile of genes involved in the biosynthesis of menthol were evaluated.ResultsOur results showed that maximal yield (wet and dry biomass) was achieved under greenhouse condition and the red‐blue LED. Application of the red‐blue LED resulted in maximal production of beneficial monoterpenes, which indicate superiority to greenhouse environment. A significant change in the gene expression profile was observed among plants grown under different light treatments. The red‐blue LED was associated with a significant up‐regulation of key genes in the menthol biosynthesis (menthol dehydrogenase and pulegone reductase). This phenomenon was consistent with a higher menthol production under the same condition.ConclusionThe application of red‐blue LED was associated with the highest level of yield and menthol production, whereas it resulted in lower concentrations of unfavorable by‐products (isomenthol, cis‐pulegone, and menthofuran). In conclusion, 70:30 red‐blue LED can be satisfactory applied to maximize growth yield and optimize favorable bioactive constituent in peppermint.

Improved Persistence of Bacteriophage Formulation with Nano N-Acetylcysteine-Zinc Sulfide and Tomato Bacterial Spot Disease Control.

Bacteriophages are biocontrol agents used to manage bacterial diseases. They have long been used against plant pathogenic bacteria; however, several factors impede their use as a reliable disease management strategy. Short-lived persistence on plant surfaces under field conditions results mainly from rapid degradation by exposure to ultraviolet (UV) light. Currently, there are no effective commercial formulations that protect phages from UV. The phage ΦXp06-02-1, which lyses strains of the tomato bacterial spot pathogen Xanthomonas perforans, was mixed with different concentrations of the nanomaterial N-acetylcysteine surface-coated manganese-doped zinc sulfide (NAC-ZnS; 3.5 nm). In vitro, NAC-ZnS at 10,000 μg/ml formulated phage, when exposed to UV for 1 min, provided statistically equivalent plaque-forming unit (PFU) recovery as phages that were not exposed to UV. NAC-ZnS had no negative effect on the phage's ability to lyse bacterial cells under in vitro conditions. NAC-ZnS reduced phage degradation over time in comparison with the nontreated control, whereas N-acetylcysteine-zinc oxide (NAC-ZnO) had no effect. In fluorescent light, without UV exposure, NAC-ZnO-formulated phages were more infective than NAC-ZnS-formulated phages. The nanomaterial-phage mixture did not cause any phytotoxicity when applied to tomato plants. Following exposure to sunlight, the NAC-ZnS formulation improved phage persistence in the phyllosphere by 15 times compared with nonformulated phages. NAC-ZnO-formulated phage populations were undetectable within 32 h, whereas NAC-ZnS-formulated phage populations were detected at 103 PFU/g. At 4 h of sunlight exposure, NAC-ZnS-formulated phages at 1,000 μg/ml significantly reduced tomato bacterial spot disease severity by 16.4% compared with nonformulated phages. These results suggest that NAC-ZnS can be used to improve the efficacy of phages for bacterial diseases.

Fluorescence Activity-Guided Isolation of Aaptamine Derivatives From the Marine Sponge Aaptos suberitoides and Their Inhibitory Activity Against Transient Receptor Potential Ankyrin 1

Objective: The aim of this research was to isolate and identify the natural products responsible for the biological and fluorescence activity of the extract from the marine sponge Aaptos suberitoides. Methods: Fluorescence activity-guided separation was performed after validation of the inhibitory activity of the extract against human transient receptor potential ankyrin 1 (hTRPA1) and subsequent measurement of its fluorescence activity. Three previously reported marine alkaloids, aaptamine, isoaaptamine, and 9- O-demethylaaptamine, were obtained and identified based on their nuclear magnetic resonance and high-resolution mass spectrometry data. Results: Aaptamine showed emission of the fluorescent light at a wavelength of 485 nm with a quantum yield of 31%. Isoaaptamine and 9- O-demethylaaptamine showed marginal fluorescence activity but promising inhibitory activity against hTRPA1 with IC50 values of 3.1 and 3.9 μM, respectively. Conclusions: This research demonstrates that natural fluorophores can be discovered in living organisms through photoactivity-guided isolation. Aaptamine, isolated as a result, provides an additional 1,6-naphthyridine fluorophore, while isoaaptamine and 9- O-demethylaaptamine suggest a chemical scaffold that could be used to study the function of ion channels.

Fluorescent Lighting’s Impact on Academic Performance of High Schoolers

Fluorescent Lighting maintains its prominence in schools, offices, and businesses across the country due to its cheapness and effectiveness, though its nature can lead to headaches, eye discomfort, or even inability to focus. While previous researchers have delved into how this lighting affects elementary-age students, college students, and adults outside of schools, high schoolers spend far more time under fluorescent lighting averaging 7 hours a day, 5 days a week, four weeks a month, and 10 months a year. Furthermore, this extended exposure can result in more severe effects of fluorescent lighting, leaving students at a disadvantage in the classroom. Utilizing an online IQ test and symptom pre/post-tests, high school students were examined under fluorescent lighting, natural lighting, and darkened lighting with their IQ score, time needed to complete the exam, and symptom prevalence measured. The average IQ score for fluorescent lighting was 123.4 whereas for the natural lighting trial, the average score was 130.4 and darkened lighting had an average score of 127.4, and 67% of scores under fluorescent lighting were 125.5 or below whereas natural lighting demonstrated 83% of scores being 125.5 or above (125.5 was the median number out of the entire data set). Similarly, 91% of participants under fluorescent lighting needed 11 minutes and 23 seconds or more to complete the test whereas 83% of participants under natural lighting needed 11’23” or less to complete the test (11' 23” was the median number out of all the data collected).

Fluorescence and Near-Infrared Light for Detection of Secondary Caries: A Systematic Review.

Early detection of secondary caries near dental restorations is essential to prevent further complications. This systematic review seeks to evaluate the sensitivity of fluorescence and near-infrared (NIR) imaging techniques for detecting secondary caries and to provide insight into their clinical utility. A comprehensive search strategy was used to select studies from seven databases, emphasizing diagnostic accuracy studies of secondary caries detection using fluorescence and NIR imaging techniques. The Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) instrument assessed bias risk and practicality. Two evaluators performed data extraction, screening, and quality assessment independently. From 3110 initial recordings, nine studies were selected for full-text analysis. Wide variations in sensitivity (SE) and specificity (SP) values were reported across the studies. These studies exhibited variable SE and SP values, and the findings highlighted the importance of method selection based on clinical context. This systematic review underlines the potential for fluorescence and NIR imaging to detect secondary caries. However, results from different studies vary, indicating the need to consider additional variables such as restoration materials. Although these technologies exhibit potential for detecting caries, our research underscores the complex procedure of identifying secondary caries lesions. It is a continuous necessity for progress in dental diagnostics to promptly identify secondary caries lesions, particularly those in proximity to tooth-colored ones.