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Two dimensional Dion-Jacobson (2D DJ) perovskite has emerged as a potential photovoltaic material because of its unique optoelectronic characteristics. However, due to its low structural flexibility and high formation energy, extra assistance is needed during crystallization. Herein, we study the solvent effect on film formation and trap states of 2D DJ perovskite. It is found that the nucleation process of 2D DJ perovskite can be retarded by extra coordination, which is proved by in situ optical spectra. As a benefit, out-of-plane oriented crystallization and ordered phase distribution are realized. Finally, in 1,5-pentanediammonium (PeDA) based 2D DJ perovskite solar cells (PSCs), one of the highest reported open-circuit voltage (

As one of the subtle reservoirs, low-resistivity-low-contrast (LRLC) pay zones are crucial potential exploration objective in Ordos basin. However, since its resistivity similarity to the adjacent water zones, and the genetic mechanism is complex, thence, LRLC pay zones still produce hydrocarbon at minimum resistivity contrast between hydrocarbon-bearing intervals and water-wet or shaly zones. So, if LRLC pay zones could be accurately identified only by conventional logging curves, it would bring new reserves to the development of Yanchang Oilfield. Focusing on the difficulties in well logging identification of Chang 2 LRLC pay zones in Zhidan area of Ordos basin, the work on logging identification of low resistivity pay zones in this area is carried out by processing field data such as drilling coring, well logging curves, oil testing and daily production data. Meanwhile, combined with the experimental data such as NMR experiments, rock electrical experiments, laser particle size and cation exchange capacity experiments, we form an integrated workflow based on petrography, rock typing and petrophysical methods, and deal with the identification, characterization and evaluation of LRLC pay zones. This study indicates that under the deposition environment of delta plain subfacies, Chang 2 reservoir is dominated by medium-fine-grained feldspar sandstone, and the pore structure is extremely complex due to the strong compaction. Therefore, the key cause for LRLC pay zones is the high salinity of formation water, accompanied by secondary reasons such as complex pore structure, and additional electron conductivity of the clay. In order to effectively identify the pay zones, we establish a set of suitable logging curve interpretation models based on the "four properties" relationship and test them with oil testing data, which could improve the accuracy of these models. Finally, the "apparent formation water resistivity - deep induced resistivity" cross-plot, the adjacent water zone comparison and the multivariate discriminant methods are selected to be suitable for Chang 2 low resistivity pay zones in the area. And these methods could help engineers to better estimation of water saturation in the low resistivity pay zones and accurately determine the target layer by using only limited set of well log data (conventional well logging data). In this work, three effective logging identification methods have been proposed to determine the advantaged pay zones from qualitative or quantitative perspectives. Through real block verification, these methods could effectively improve the coincidence rate of logging identification, and would provide bases for selecting the target layers in original development areas. More importantly, the results may offer new perspectives for risk assessment and target layer determination of other similar low resistivity reservoirs exploration and development.

The surface-enhanced Raman scattering (SERS) technique has attracted increasing attention in biomedicine due to the capability of providing the molecular fingerprint information of biosamples. Two-dimensional (2D) metal nanohybrids have proven to be efficient SERS substrates for bioanalysis due to the cooperative Raman enhancement mechanism. Herein, a facile strategy for the fabrication of a novel transition metal telluride-based 2D-metal SERS substrate is proposed. Ag-niobium ditelluride (NbTe

Although the photovoltaic performance of perovskite solar cells (PSCs) has reached the commercial standards, the unsatisfactory stability limits their further application. Hydrophobic interface and encapsulation can block the damage of water and oxygen, while the instability induced by intrinsic residual strain remains inevitable. Here, the residual strain in a two-dimensional (2D) Ruddlesden-Popper (RP) perovskite film is investigated by X-ray diffraction and atomic force microscopy. It's found that the spacer cations contribute to the residual strain even though they are not in the inorganic cages. Benefited from strain relaxation, the film quality is improved, leading to suppressed recombination, promoted charge transport and enhanced efficiency. More significantly, the strain-released devices maintain 86 % of the initial efficiency after being kept in air with 85 % relative humidity (RH) for 1080 h, 82 % under maximum power point (MPP) tracking at 50 °C for 804 h and 86 % after continuous heating at 85 °C for 1080 h.

In this work, three novel nonmetallic pentazole salts (6–8) based on furazan or 4-nitropyrazole were synthesized. Some coplanar groups were introduced into the compounds to improve the planarity of...

A new symmetric compound 3,5-bis(3-amine-4H-1,2,4-triazole)-1H-pyrazole and a series of corresponding energetic salts 5–9 were synthesized. All the new compounds were fully characterized by spectroscopy (IR, NMR, and elemental) analyses and differential scanning calorimetry (DSC). Compound 6 was further investigated by X-ray crystal-structure analysis. Various performance tests of all the compounds, such as density, thermal behavior, mechanical sensitivity and detonation property, were tested. All the target compounds showed relatively positive calculated heat of formation (24.9 to 2396.4 kJ mol−1), good mechanical sensitivity (IS > 24 J, FS > 280 N) and acceptable detonation property (D > 7400 m s−1, P > 19.5 GPa). In particular, energetic salt 9 exhibits prominent detonation property (D > 8964 m s−1, P > 37.1 GPa) and excellent sensitivity (IS > 40 J, FS > 360 N), which show its potential application prospects as a new high energy insensitive material.

We report a genome-wide association study for facial features in > 6,000 Latin Americans. We placed 106 landmarks on 2D frontal photographs using the cloud service platform Face++. After Procrustes superposition, genome-wide association testing was performed for 301 inter-landmark distances. We detected nominally significant association (P-value − 8) for 42 genome regions. Of these, 9 regions have been previously reported in GWAS of facial features. In follow-up analyses, we replicated 26 of the 33 novel regions (in East Asians or Europeans). The replicated regions include 1q32.3, 3q21.1, 8p11.21, 10p11.1, and 22q12.1, all comprising strong candidate genes involved in craniofacial development. Furthermore, the 1q32.3 region shows evidence of introgression from archaic humans. These results provide novel biological insights into facial variation and establish that automatic landmarking of standard 2D photographs is a simple and informative approach for the genetic analysis of facial variation, suitable for the rapid analysis of large population samples.

Objective: To adapt the oral health-related quality of life (OHRQoL) measurement tool SOHO-5 (scale of oral health outcomes for 5-year-old children) for use in Chinese populations, and to investigate the validity and reliability of the Chinese version of SOHO-5 (C-SOHO-5). Materials and methods: The draft C-SOHO-5 was developed by a forward–backward process and pilot-tested on 20 child–parent pairs. The final version was tested on a sample of 5-year-old children and their parents. Clinical examinations were conducted to record the children’s caries experience. The reliability of C-SOHO-5 was assessed by both internal consistency and test—retest reliability. Its discriminant validity and construct validity were also investigated. Results: A total of 249 child–parent pairs participated in this study. Cronbach’s alpha values for the child’s version of C-SOHO-5 (C-SOHO-5c) and the parental version of C-SOHO-5 (C-SOHO-5p) were 0.71 and 0.82, respectively. The intraclass correlation coefficient values for C-SOHO-5c and C-SOHO-5p were 0.85 and 0.46, respectively. Both the child’s and the parental version were able to discriminate the caries and caries-free children groups. Children with caries experience had higher mean ranks of the total score of both C-SOHO-5c and C-SOHO-5p than those of the caries-free children (134.9 vs. 113.8, P = 0.015; 134.7 vs. 93.2, P < 0.001). In addition, the total scores of both child’s and parental reports were significantly correlated with the global rating questions. Conclusion: The C-SOHO-5 demonstrated good reliability and validity. This tool, which uses both child’s and parental reports, can be used to assess the OHRQoL of 5-year-old children in Chinese-speaking communities.

High-performance energetic materials require good balance between energy and safety, which may be achieved through structural design. Herein, an energetic compound containing a furazan-triazole backbone linked by methylene bridges and a systematic series of corresponding energetic salts were synthesized, characterized structurally, and subjected to various performance tests. All the target compounds possessed good impact sensitivities (IS ​> ​24 ​J) and friction sensitivities (FS ​> ​240 ​N), as well as acceptable detonation velocities (D ​> ​7756 ​m ​s−1) and detonation pressures (p ​> ​23.6 ​GPa). In addition, the detonation performance of each salt was enhanced to some extent compared with that of the corresponding neutral compound. Moreover, a combination of theoretical calculations and the energetic performance parameters was used to elucidate the structure–property relationship of the target compounds. These findings will enrich future prospects for the design of insensitive energetic materials.

Objective This study aimed to investigate the association between oral health-related quality of life (OHRQoL) and caries experience of Hong Kong preschool children. Methods Parents or primary caregivers of Hong Kong preschool children were invited to complete a self-administered dental health questionnaire. The study children were examined in their classrooms. The decayed, missing and filled primary teeth (dmft) index was used for documenting the caries status. The questionnaire included the Chinese Early Childhood Oral Health Impact Scale (ECOHIS) and collected sociodemographic information on the parents and children. Logistic regression analysis was used to determine the association between OHRQoL and caries experience of preschool children. Results A total of 434 preschool children were invited to participate in the study; 336 (77.4%) received a dental examination and returned a parental questionnaire. The mean (SD) age of the study children was 4.7 (0.3) years. An OHRQoL impact (ECOHIS score of >0) for at least one item was reported by 236 (70.2%) parents/caregivers of the children included in the study. The overall mean (SD) ECOHIS score was 5.8 (6.2). A caries prevalence (dmft > 0) of 36.9% and a mean (SD) dmft score of 1.7 (3.2) were calculated for the study children. In the final logistic regression model, children with a higher dmft score had a significantly higher chance of having a poorer OHRQoL (OR = 1.20, 95% CI: 1.07-1.35, P = 0.002), whereas children's sex, parent's education levels and the respondent's relationship to the child were not associated with OHRQoL (P > 0.05). Conclusion Caries experience is associated with lower OHRQoL of Hong Kong preschool children.

Background Silver diamine fluoride (SDF) solution is effective in arresting early childhood caries (ECC). Previous studies have suggested that it might exert a preventive effect in managing ECC. However, no well-designed clinical trials have yet been performed to study the effect of SDF on caries prevention. The objective of this randomised clinical trial is to determine whether 38% SDF solution is superior to 5% sodium fluoride (NaF) varnish in preventing new carious lesions in primary anterior teeth. Methods/design This is a phase II, single-centre, randomised, double-blind, active-controlled, parallel-group pragmatic trial. The hypothesis tested is that 38% SDF would be more effective than 5% NaF in preventing new caries development in primary anterior teeth. Approximately 730 3-year-old children who are generally healthy and with parental consent will be recruited from Hong Kong kindergartens. This sample size will be sufficient for appropriate statistical analysis of a superiority trial with 90% power, allowing for a 20% drop-out rate. Stratified randomisation will be adopted for allocating the intervention. The intervention will either be 38% SDF or 5% NaF (as a positive control) therapy on primary upper anterior teeth. A single trained examiner will conduct a dental examination every 6 months until 30 months in kindergarten. Another operator will provide fluoride therapy immediately after each dental examination. The examiner, children and children’s parents will be blinded to the treatment allocation. A questionnaire survey will be conducted to study the children’s oral health-related behaviours and socioeconomic backgrounds. Chi-square tests, t tests, regression analyses and survival analyses will be adopted for data analysis. Discussion The effectiveness of 38% SDF in preventing ECC remains uncertain. If the results are as anticipated, care standards using 5% NaF for ECC prevention will be changed. In addition, the results will be widely available and increase the adoption of SDF in other countries to reduce the global burden of ECC. Trial registration ClinicalTrials.gov, NCT04075474. Registered on 30 Aug 2019.

The intramolecular cyclization reaction of picrylhydrazone into an indazole derivative was systematically studied. The optimized conditions, mechanism and the generality of the cyclization reaction from picrylhydrazone to indazole were investigated. Picrylhydrazones 1a–6a and indazole derivatives 1b and 3b–7b were synthesized through a one-step reaction and the crystal structures of 2a, 4a and 5b were characterized by single crystal X-ray diffraction analysis. Among all the compounds, the indazole derivatives exhibit an increase of 24–341 m s−1 (0.3–4.3%), 0.6–3.1 GPa (2.2–14.3%) and 9–82 °C (5.0–44.0%) in detonation performance and thermal stability as well as a decrease of 4–10 J (15.4–33.3%) and 50–120 N (16.1–50.0%) in mechanical sensitivity to impact and friction compared with picrylhydrazones. Furthermore, the structure–property relationship was demonstrated by a combination of fingerprint plots, Hirshfeld surfaces and explosive properties. All those results demonstrated that this study can enrich the future prospects of the design of energetic materials.

Property modulation of graphene glass by heteroatom doping such as boron (B) and nitrogen (N) is important to extend its practical applications. However, unlike N doping, research studies about the metal-free synthesis of B-doped graphene on glass through the chemical vapor deposition (CVD) method are rarely reported. Herein, we report a hot-filament CVD approach to prepare B-doped graphene glass using diborane (B2H6) as the B dopant. The synthesized B-doped graphene was uniform on a large-scale and composed of nanocrystalline graphene grains. By raising the B2H6 flow from 0 to 15 sccm, the B content of graphene was facilely modulated from 0 to 5.3 at. %, accompanied with the improvement of both transparency and conductivity. The B-doped graphene prepared on glass at 15 sccm B2H6 flow presented the optimal transparent conductive performance superior to those of most reported graphene glass fabricated by other state-of-the-art approaches. Furthermore, for the first time, the performance of graphene glass for wave energy harvesting has been elaborated. It was found that the output power produced by inserting graphene glass into 0.6 M sodium chloride (NaCl) solution could be improved by more than 6 times through B doping. The significant enhancement resulted from the higher waving voltage and smaller resistance of B-doped graphene on glass than the pristine ones. In addition, the waving voltage inversed the polarity after B doping, which was due to the opposite variation of surface potential of pristine and B-doped graphene after NaCl immersion. This work would pave ways for the metal-free preparation and expand the energy-harvesting applications of B-doped graphene materials.

This study aimed to explore parental perspectives on an outreach dental service and silver diamine fluoride (SDF) therapy to arrest and prevent early childhood caries.This qualitative study collaborated with an outreach service offering SDF therapy to kindergarten children and oral health education to the children's parents. The study was conducted in 2018 using purposive sampling of participating parents from selected kindergartens in Hong Kong until data saturation was reached. Five parents were recruited from each kindergarten for a focus-group discussion. The data were manually coded for thematic analysis.Ten focus-group discussions with 49 parents were held to achieve data saturation. The oral health education largely met the parents' expectations regarding enriching their child's oral health knowledge, raising their child's dental awareness, and promoting parent-assisted toothbrushing. Some parents did not consent to their children undergoing SDF therapy because it permanently stains caries black, which adversely affects appearance. They were also concerned about potential toxicity of SDF. Parents who did consent preferred the arrest and prevention of dental caries over aesthetics which are temporary until the primary teeth exfoliate.This outreach dental service improved parental dental knowledge. Some parents were generally satisfied with the outreach dental services, preferred caries arrest over aesthetics, and accepted SDF therapy. However, some parents worried about SDF toxicity. The results of this study provide rich, in-depth, and multi-dimensional information about parents' experiences of taking the outreach dental service and their opinions about SDF therapy.Dentists can use the arguments from this study to form a protocol for communicating with parents before SDF therapy. This study shows that outreach dental services improve dental knowledge. Some parents prefer caries arrest over aesthetics and accept SDF therapy; however, some parents worry about SDF toxicity.

Background: The Yi ethnic group is the sixth largest minority in China. The aim of this study was to investigate dental caries status among Yi preschool children in the Yunnan province, China. Method: This cross-sectional study invited 5-year-old Yi children using multistage cluster sampling. Two trained and calibrated dentists examined the children in kindergartens. The children’s dental caries experience was assessed using the decayed, missing, and filled teeth (dmft) index. Visual plaque on an indexed tooth of each six sextants was recorded and the oral hygiene status was assessed using the Visible Plaque Index. Parents completed questionnaires that surveyed their educational attainment. The questionnaires also collected information about the children’s demographics, snacking habits, oral-health-related behaviors and dental visit experiences. The associations between caries experiences and potential factors were analyzed using zero-inflated negative binomial regression. Results: All 452 invited children (249 boys, 55%) participated in this study with a response rate of 100%. Dental caries prevalence rate was 83%. The mean dmft score and decayed teeth score were 5.2 ± 4.4 and 5.1 ± 4.4, respectively. Almost half of the children (n = 211, 47%) had visible plaque on four or more of the six sextants. Most (n = 366, 81%) of the children had not visited a dentist in the prior 12 months. Regression analysis found the children’s caries experience was associated with their dental visit experience. Conclusion: The great majority of the Yi preschool children experienced dental caries and almost all of the cavities were not restored. Their oral hygiene was poor and visible plaque was commonly found on their teeth.

Facial morphology, the most conspicuous feature of human appearance, is highly heritable. Previous studies on the genetic basis of facial morphology were mainly performed in European populations. Applying a proven data-driven phenotyping and multivariate genome-wide scanning protocol to the largest collection of 3D facial images of an East Asian population to date, we identified 244 leading variants associated with normal-range facial variation, of which 130 are novel. A newly proposed polygenic shape analysis indicates that the effects of the variants on East Asian facial shape can be generalized into the European population. Based on this analysis, we further identified 13 variants mainly related to differences between European and East Asian facial shape. Natural selection analyses suggest that the difference in European and East Asian nose shape is caused by a directional selection, mainly due to a local adaptation in Europeans. Our results expand the knowledge of human facial genetics and illustrates for the first time the underlying genetic basis for facial differences across populations.

Aim:Early childhood caries (ECC) has significant public health implications but has received inadequate global attention. There is limited information regarding the success of oral health policies implemented to address the challenges of ECC. This review aimed to summarize such policies to tackle ECC from different countries/regions.Method:Independent collaborators from 14 countries/regions (Australia, Brazil, Cambodia, China, Hong Kong, Egypt, India, Indonesia, Japan, Nigeria, Thailand, UK, USA, and Venezuela) collected the data. The ECC status, dental workforce, oral health policies on ECC prevention in different countries/regions were summarized by each country.Results:The findings indicated that ECC prevalence varied in different countries/regions. The lowest prevalence of ECC among 5-year-old children was found in Nigeria (7%), and the highest was found in Indonesia (90%). The existing dental workforce and resources are limited in most countries. The smallest dentist to population ratio was reported by Nigeria at 1:48,400, whereas the highest ratio was in Brazil (1:600). Out of 14, three (21%) countries namely India, Venezuela and Cambodia had no national oral health policies addressing ECC and four (29%) countries (Cambodia, China, India, Venezuela) had no publicly funded dental care program for 0–5-year-old children. Water fluoridation is available in four countries/regions (Australia, Brazil, Hong Kong, USA).Conclusion:ECC remains a global health challenge and dental workforce is limited. National/regional programs to tackle ECC are not yet prioritized in many countries/regions. Evidence to support demonstration projects is limited. Further research on the cost-effectiveness of interventions strategies is required for policymakers.

In this work, antimony selenide (Sb2Se3) thin films were prepared using electron-beam (e-beam) evaporation followed by selenization process (two-step method) for the first time. The effect of selenization temperature on the properties of Sb2Se3 thin films and solar cells was investigated systematically. Formation of pure polycrystalline Sb2Se3 was confirmed and the intensity of (hk1) and (hk2) patterns was found to decrease while that of (hk0) to increase with temperature elevating. However, when the temperature became higher than 360 °C, the shape of Sb2Se3 grains gradually changed to rod-like shape from round shape and some craters and cracks in the films can be observed. Sb2Se3 films prepared at 360 °C showed an average grain size of 450 nm, a roughness of 42 nm, an optical bandgap of 1.24 eV and a carrier concentration of 4.99 × 1012 cm−3. The corresponding Sb2Se3 solar cells exhibited an optimal power conversion efficiency of 1.15%. Our results demonstrated that the process of e-beam evaporation of Sb followed by selenization at appropriate temperature is a good way to prepare high quality Sb2Se3 thin films for solar cells.

Metal-free synthesis of nitrogen-doped (N-doped) graphene films on glass is important for modulating the properties of graphene glass but has so far met with limited success. In this study, direct synthesis of N-doped graphene films on glass with eco-friendly N2 dopant through a novel plasma-assisted hot filament chemical vapor deposition (HFCVD) approach was reported. Influence of plasma power on the structural and electrical properties of N-doped graphene films was investigated. The filament and plasma source were found to be both crucial for depositing high-quality N-doped graphene films with N2 dopant. With a small N2 flow of 5 sccm, the N content of graphene films synthesized by plasma-assisted HFCVD could be modulated from 0.6 to 3.0 at.% through adjusting the plasma power from 0 to 130 W. A lowest resistivity of 4.68 × 10−3 Ω cm was obtained at 130 W. Temperature-dependence of resistance measurement revealed that the carrier mobility of N-doped graphene films decreased by raising the plasma power, which was attributed to the increase of conductive activation energy. This work provides an alternative method for direct, controllable and green preparation of N-doped graphene films on glass.

Objective: The aim of this study was to describe the prevalence of dental caries among 3- to 5-year-old children in Hong Kong and to investigate the factors associated with their dental caries status. Methods: Seven kindergartens in Hong Kong were selected using stratified random sampling. The 3- to 5-year-old kindergarten children were invited to join the study. The participants’ parents were asked to complete a questionnaire regarding their children’s demographic and socio-economic backgrounds, their dental habits and their own dental knowledge. Dental caries experience was measured using the decayed, missing and filled primary teeth (dmft) index. The visible plaque index was adopted for recording oral hygiene. The relationships between caries experience and children’s demographic backgrounds, dental habits, oral hygiene and parental dental knowledge were studied using a zero-inflated negative binomial (ZINB) regression analysis. Results: Among the 1,204 participating preschool children, the overall prevalence of dental caries (dmft > 0) was 46%. The mean dmft score was 2.1 ± 3.4. The prevalences of dental caries among the 3-, 4- and 5-year-old children were 38%, 43% and 55%, respectively. ZINB regression analysis revealed that the study children who were boys, came from families with lower incomes, had dental visit experiences, had higher plaque scores and had parents with lower levels of dental knowledge, had higher dmft scores (P < 0.05). Conclusions: Dental caries is prevalent among preschool children in Hong Kong. The caries experiences of the study children are associated with gender, family income, parental dental knowledge, dental visit experience and oral hygiene.

It is difficult for triboelectric nanogenerators (TENG) to harvest energy with high humidity environments, due to the screening effect of water. The resistance of TENG with atmosphere humidity has been studied by many previous works, while the energy generation of TENG on highly wetted or even water-bearing surface has not been thoroughly studied. Hence, we propose an octopus tentacle inspired micro patterns on the interface of TENG, which can provide two kinds of functions. The honeycomb-shaped micro patterns on tribo-electrification interface can maintain the energy generation on highly wetted condition and the similar patterns on the hydrogel surface can also achieve good adhesive capability on water-bearing substrates. The contact interface with honeycomb-shaped micro patterns can facilitate the water drainage during the pressing motion, which can increase the effective contact area for electrification. The open-circuit voltage (Voc) of the TENG with patterned tribo surface can reach 78 V on highly wetted surface, which is two times higher than that of a planar device. On the other hand, the similar honeycomb-shaped micro patterns have been applied on the surface of tough PA hydrogel. Accordingly, a hydrogel based TENG with repeatable adhesive capability is prepared, which allows TENG device to be adhered on the water-bearing substrate and harvest water wave energy. The demonstrated designed concept of this honeycomb-shaped micro patterns interface has excellent applicability in water-bearing environment and water wave energy harvesting process, enhancing device usability and promoting its practical applications.

Flexible Cu(InGa)Se2 (CIGS) solar cells on metallic substrates are highly desirable for versatile energy applications. However, related researches reported on CIGS devices usually used a diffusion barrier, which involves an issue of thermal expansion coefficient matching and complicates the fabrication process. In this study, CIGS solar cells were fabricated on Ni and Ti foils through selenization of metal stacks deposited by e-beam evaporation, without the use of diffusion barrier. The films on Ti foils showed (112) preferred orientation while those on Ni foils exhibited (220) preferred orientation, due to the different crystal orientation of substrates. In–Ni and Ga–Ni phase were observed in films prepared on Ni foils, which led to the existence of Cu2–xSe. As a result, the CIGS solar cells fabricated on Ni foils showed inferior photoelectric properties, whereas those on 50 and 100 μm Ti foils presented conversion efficiency of 4.9% and 6.6%. The discrepancy on efficiency between two cells on Ti foils was ascribed to the different structural properties induced by the thermal stress. After 100 bending cycles, efficiency of cells on 50 and 100 μm thick Ti foils decreased by 1.0% and 2.6% respectively, indicating that CIGS solar cell on 50 μm Ti foil is more promising as flexible device applied on harsh circumstance.

Deposition pressure is an important factor for the preparation of amorphous carbon (a-C) films through vacuum method. However, researches about the properties, especially optical and electrical properties of a-C films influenced by deposition pressure are still rare. In this work, hot-filament chemical vapor deposition (HFCVD) was used to deposit conductive a-C films under different deposition pressure conditions. As deposition pressure raised from 5 to 160 Pa, a structural transition from a-C to nanocrystalline graphite that led to the increase of cluster size, sp2 content and crystalline quality of a-C films was observed. The hybrid structure composed of amorphous and nanocrystalline phases was also revealed by high-resolution transmittance electron microscope. The mobility, transmittance and conductivity of films increased while the optical gap and carrier concentration decreased by elevating the deposition pressure. As a result, a-C films prepared at 160 Pa showed the best property with a roughness of 0.412 nm, a transmittance of 67%, an optical bandgap of 1.25 eV, a resistivity of 75 μΩ m and a mobility of 3.17 cm2 V−1 s−1, which is comparable to those prepared through other methods. The small roughness, good transmittance and low resistivity implied that high quality a-C films can be prepared through HFCVD method by adjusting the deposition pressure.

Objectives The aim of the study was to investigate the effect of silver diamine fluoride (SDF) therapy on the oral health-related quality of life (OHRQoL) of preschool children and their families in a school-based setting. Methods A prospective study was conducted in six kindergartens in Hong Kong. Parents of the children were invited to complete an oral health questionnaire and to have their child undergo a dental examination. The decayed, missing and filled teeth (dmft) index was adopted for recording oral health status. The Chinese Early Childhood Oral Health Impact Scale (C-ECOHIS) was used to evaluate the OHRQoL of the children and their families. Children with untreated caries were treated with SDF. The Wilcoxon Signed Ranks Test was used to determine the changes in C-ECOHIS scores before and after SDF treatment for six months. Results At baseline, 117 preschool children aged 4–5 years received SDF treatment for caries arrest. Their mean(SD) dmft score at baseline was 4.9(3.8). After six months, 113(96.6%) returned a completed questionnaire. Their mean(SD) C-ECOHIS scores at baseline and follow-up were 7.4(6.6) and 7.8(6.4), respectively. The overall differences between pre- and post-treatment scores were not significant (p = 0.301). Concerning parent section, a negative impact was found (p = 0.014), whereas no significant impact was found in the child section (p = 0.831). Conclusion Based on the 6-month results, the SDF treatment conducted in a school setting did not affect the overall OHRQoL of preschool children and families. Clinical significance These results can provide important information to dental professionals regarding the use of SDF for caries control.

Nitrogen (N) doping is an efficient way to modulate the properties of graphene. The reported chemical vapor deposition (CVD) processes for synthesizing N-doped graphene mostly involve a metal catalyst and ammonia (NH3) dopant. However, the inevitable metal residual and toxicity of NH3 would significantly hinder its practical applications. In this paper, for the first time, metal-free synthesis of N-doped graphene films on glass was achieved through a plasma-assisted hot filament CVD method using eco-friendly N2 gas as the dopant. Both the hot filament and plasma source were proven to be essential for growing N-doped graphene of preferable quality. By adjusting the N2 flow, the N content, transmittance and electrical properties of graphene films could be facilely modulated. Furthermore, it was demonstrated that the electrical voltage induced by dropping ion droplets on graphene glass was significantly improved from 50 mV to 320 mV through N doping, exceeding those of reported graphene based electricity generators. This improvement was attributed to the higher surface potential of N-doped graphene glass compared to the pristine ones, as revealed by Kelvin probe force microscopy. The present work provides a promising strategy for direct synthesis and expands applications of N-doped graphene glass for high-efficiency energy harvesting.

Surveys have shown that the prevalence of early childhood caries (ECC) among 5-year-old children decreased from 63% in 1993 to 55% in 2017. Caries experience was unevenly distributed; 81% of the caries lesions were found in 26% of the children. Risk factors, including oral hygiene practice behaviors, sugar consumption, parental oral health-related knowledge, and sociodemographic backgrounds, were significantly related to ECC. Oral health promotion aimed at managing the burden of ECC has been implemented. Water fluoridation was launched in 1961, and the fluoride concentration has been adjusted to 0.5 ppm since 1988. It is considered an important dental public health measure in Hong Kong. The Department of Health set up the Oral Health Education Unit in 1989 to deliver oral health education to further improve the oral health of preschool children. Other nongovernmental organizations also launched short-term oral health promotion programs for preschool children. However, no significant change in the prevalence of ECC has been observed in the recent two decades. There is a necessity to revisit dental public health policies and develop effective evidence-based strategies to encourage changes in oral health-related behaviors to forestall the impending epidemic of ECC in Hong Kong.

Background: The aim of this cross-sectional study was to investigate the oral health status of Hani 12-year-old children in Yunnan, a province in Southwest China. Method: This study employed a multistage sampling method to recruit children from local primary schools. Two calibrated dentists examined the status of dental caries, gingival bleeding and dental fluorosis by adopting the diagnosis criteria recommended by the World Health Organization. A self-administrated questionnaire was distributed. The chi-square test and multivariate logistic regression were conducted. Results: This study invited 480 Hani children, and recruited 413 children (52% boys) (response rate: 86%). The dental caries prevalence was 52%, and the caries experience associated with the mean (standard deviation) decayed, missing and filled teeth (DMFT) score was 1.10 (1.46). Gingival bleeding was diagnosed in 252 children (61%), and dental fluorosis was found in two children (0.5%). The results of the regression model indicated the prevalence of dental caries were associated with sugary snacking habits (p = 0.002). The prevalence of gingival bleeding was related to the mother’s education level as well as the child’s monthly pocket money (p &lt, 0.05). Conclusion: Dental caries and gingival bleeding were prevalent among 12-year-old Hani children in the Yunnan province in China. Dental fluorosis was uncommon.

Background Silver diamine fluoride (SDF) and sodium fluoride (NaF) are widely used for caries management. The objectives of this study are (i) to compare the caries-arresting and caries-preventive effects of SDF and NaF in young children, (ii) to determine children’s and parents’ acceptance of these fluoride therapies and (iii) to investigate the short-term (1 day) and long-term (1 year) adverse effects of these fluoride therapies. Methods/design This is a randomised, double-blind, active-controlled clinical trial to be conducted in Hong Kong kindergartens. The study has received approval from the local institutional review board. Written consent will be obtained from the parents/guardians before the study. The study will recruit at least 688 healthy 3-year-old children. This sample size is sufficient for an appropriate statistical analysis. Stratified randomisation will be performed for intervention allocation. The two intervention groups are 38% SDF and 5% NaF varnish applied on six primary upper anterior teeth. At baseline, one trained examiner will perform clinical examinations of the children in the kindergartens. The caries experience and oral hygiene status of each child will be recorded using the decayed, missing (due to caries) and filled primary tooth index and visual plaque index, respectively. Then, an independent operator will apply the assigned fluoride after the dental examinations. The examiner, the children and their parents will be blinded to the intervention allocation. In addition, a research assistant will evaluate the child’s acceptance using interval rating scales for children’s uncooperative behaviour. The examiner will then visit the children the next day to study the short-term potential adverse effects of the fluoride therapies. The same examiner will perform a follow-up examination after 1 year to evaluate the children’s caries experiences, their oral hygiene statuses and the adverse effects of the fluoride. Parental questionnaires will be used to assess parental satisfaction and concerns about the fluoride therapies. Discussion This study provides essential information about using SDF in an outreach kindergarten service for caries management from different aspects, which include the caries-arresting and caries-preventive effects, the adverse effects and children’s and parents’ acceptance. The success of the service can help to increase the adoption of SDF to reduce the global burden of early childhood caries. Trial registration ClinicalTrials.gov NCT04399369. Registered on May 2020

Qualitative research collects non-numerical data that explores human behaviour, attitudes, beliefs and personality characteristics unamendable to quantitative research. The qualitative research questions are open-ended, evolving and non-directional. The study design is flexible and iterative. Purposive sampling is commonly used. The sample size is determined by theoretical saturation. Data collection is generally through in-depth interviews, focus groups and observations. Qualitative research commonly uses thematic analysis and framework analysis, although there is no consensus on analysing qualitative data. The reporting format can be comprehensive, a summary, developmental or selective, subject to the research question. Qualitative research’s potential functions are to describe the form or nature of what exists (contextual), to examine the reasons for or associations between what exists (explanatory), to appraise the effectiveness of what exists (evaluative), and to aid the development of strategies (generative). Qualitative research can be time consuming to conduct because it explores evolving questions; difficult to generalise because it recruits limited participants; and arduous when it comes to making systematic comparisons because responses are subjective. However, qualitative research can provide depth and detail, create openness, simulate people’s individual experiences and avoid pre-judgements. This concise review provides an overview and suggestions for dental researchers when conducting a qualitative study.

Silver diamine fluoride (SDF) was developed in Japan in the 1960s. It is a clear solution containing silver and fluoride ions. Because of its anti-bacterial and remineralizing effect, silver diamine fluoride has been used in managing dental caries for decades worldwide. This paper aims to summarize and discuss the global policies, guidelines, and relevant information on utilizing SDF for caries management. SDF can be used for treating dental caries in most countries. However, it is not permitted to be used in mainland China. Several manufacturers, mainly in Australia, Brazil, India, Japan, and the United States, produce SDF at different concentrations that are commercially available around the world. The prices differ between contents and brands. Different government organizations and dental associations have developed guidelines for clinical use of SDF. Dental professionals can refer to the specific guidelines in their own countries or territories. Training for using SDF is part of undergraduate and/or postgraduate curriculums in almost all countries. However, real utilization of SDF of dentists, especially in the private sector, remains unclear in most places because little research has been conducted. There are at least two ongoing regional-wide large-scale oral health programs, using SDF as one of the components to manage dental caries in young children (one in Hong Kong and one in Mongolia). Because SDF treatment does not require caries removal, and it is simple, non-invasive, and inexpensive, SDF is a valuable strategy for caries management in young children, elderly people, and patients with special needs. In addition, to reduce the risk of bacteria or virus transmission in dental settings, using SDF as a non-aerosol producing procedure should be emphasized under the COVID-19 outbreak.