Fabrication technology for high light-extraction ultraviolet thin-film flip-chip (UV TFFC) LEDs grown on SiC

The light output of deep ultraviolet (UV-C) AlGaN light-emitting diodes (LEDs) is limited due to their poor light extraction efficiency (LEE). To improve the LEE of AlGaN LEDs, we developed a fabrication technology to process AlGaN LEDs grown on SiC into thin-film flip-chip LEDs (TFFC LEDs) with high LEE. This process transfers the AlGaN LED epi onto a new substrate by wafer-to-wafer bonding, and by removing the absorbing SiC substrate with a highly selective SF6 plasma etch that stops at the AlN buffer layer. We optimized the inductively coupled plasma (ICP) SF6 etch parameters to develop a substrate-removal process with high reliability and precise epitaxial control, without creating micromasking defects or degrading the health of the plasma etching system. The SiC etch rate by SF6 plasma was ~46 \mu m/hr at a high RF bias (400 W), and ~7 \mu m/hr at a low RF bias (49 W) with very high etch selectivity between SiC and AlN. The high SF6 etch selectivity between SiC and AlN was essential for removing the SiC substrate and exposing a pristine, smooth AlN surface. We demonstrated the epi-transfer process by fabricating high light extraction TFFC LEDs from AlGaN LEDs grown on SiC. To further enhance the light extraction, the exposed N-face AlN was anisotropically etched in dilute KOH. The LEE of the AlGaN LED improved by ~3X after KOH roughening at room temperature. This AlGaN TFFC LED process establishes a viable path to high external quantum efficiency (EQE) and power conversion efficiency (PCE) UV-C LEDs.Comment: 22 pages, 6 figures. (accepted in Semiconductor Science and Technology, SST-105156.R1 2018

A new primary dental care service compared with standard care for child and family to reduce the re-occurrence of childhood dental caries (Dental RECUR): study protocol for a randomised controlled trial

Background: In England and Scotland, dental extraction is the single highest cause of planned admission to the hospital for children under 11 years. Traditional dental services have had limited success in reducing this disease burden. Interventions based on motivational interviewing have been shown to impact positively dental health behaviours and could facilitate the prevention of re-occurrence of dental caries in this high-risk population. The objective of the study is to evaluate whether a new, dental nurse-led service, delivered using a brief negotiated interview based on motivational interviewing, is a more cost-effective service than treatment as usual, in reducing the re-occurrence of dental decay in young children with previous dental extractions. Methods/Design: This 2-year, two-arm, multicentre, randomised controlled trial will include 224 child participants, initially aged 5 to 7 years, who are scheduled to have one or more primary teeth extracted for dental caries under general anaesthesia (GA), relative analgesia (RA: inhalation sedation) or local anaesthesia (LA). The trial will be conducted in University Dental Hospitals, Secondary Care Centres or other providers of dental extraction services across the United Kingdom. The intervention will include a brief negotiated interview (based on the principles of motivational interviewing) delivered between enrolment and 6 weeks post-extraction, followed by directed prevention in primary dental care. Participants will be followed up for 2 years. The main outcome measure will be the dental caries experienced by 2 years post-enrolment at the level of dentine involvement on any tooth in either dentition, which had been caries-free at the baseline assessment. Discussion: The participants are a hard-to-reach group in which secondary prevention is a challenge. Lack of engagement with dental care makes the children and their families scheduled for extraction particularly difficult to recruit to an RCT. Variations in service delivery between sites have also added to the challenges in implementing the Dental RECUR protocol during the recruitment phase. Trial registration: ISRCTN24958829 (date of registration: 27 September 2013), Current protocol version: 5.0

COVID-19: Training disruption and opportunities experienced by UK paediatric dentistry trainees

Introduction The COVID-19 pandemic disrupted the delivery of routine dental services in the UK. Reduced face-to-face clinical activity has resulted in reduced availability of tertiary specialist services. The impact of the pandemic on medical trainees has been explored but there is limited literature regarding dental trainees. Methods A blended questionnaire was designed, pre-piloted and administered as an online anonymous survey. Following pre-notification, this was administered to paediatric dentistry trainees for a three-week period. Quantitative data underwent descriptive statistics and qualitative data were subject to thematic analysis. Results The response rate was 63% (n=35). Two respondents were out of programme. Outpatient clinics and treatment with local anaesthesia were the most disrupted aspects of training. Academic training was less disrupted than clinical training. Thematic analysis found three key themes: personality and personal circumstance, colleagues and workplace, and changes to clinical and academic activity. Trainees perceptions ranged from optimistic to pessimistic, with many trainees identifying opportunities they had gained while others perceived none. Conclusions This survey shows variation in training disruption and opportunity during the COVID-19 pandemic. Our findings support anecdotal evidence and results emerging from trainees in medicine. Further surveys should be administered as the pandemic progresses and these should include other dental specialties

Expression of a Barhl1a reporter in subsets of retinal ganglion cells and commissural neurons of the developing zebrafish brain

Promoting the regeneration or survival of retinal ganglion cells (RGCs) is one focus of regenerative medicine. Homeobox Barhl transcription factors might be instrumental in these processes. In mammals, only barhl2 is expressed in the retina and is required for both subtype identity acquisition of amacrine cells and for the survival of RGCs downstream of Atoh7, a transcription factor necessary for RGC genesis. The underlying mechanisms of this dual role of Barhl2 in mammals have remained elusive. Whole genome duplication in the teleost lineage generated the barhl1a and barhl2 paralogues. In the Zebrafish retina, Barhl2 functions as a determinant of subsets of amacrine cells lineally related to RGCs independently of Atoh7. In contrast, barhl1a expression depends on Atoh7 but its expression dynamics and function have not been studied. Here we describe for the first time a Barhl1a reporter line in vivo showing that barhl1a turns on exclusively in subsets of RGCs and their post-mitotic precursors. We also show transient expression of barhl1a:GFP in diencephalic neurons extending their axonal projections as part of the post-optic commissure, at the time of optic chiasm formation. This work sets the ground for future studies on RGC subtype identity, axonal projections and genetic specification of Barhl1a-positive RGCs and commissural neurons

Minimal Intervention Dentistry (MID) mainstream or unconventional option? Study exploring the impact of COVID-19 on paediatric dentists' views and practices of MID for managing carious primary teeth in children across the United Kingdom and European Union

PurposeTo explore the techniques used to manage carious primary teeth during the COVID-19 pandemic by paediatric dentists and dentists with a special interest in paediatric dentistry (DwSI) who are members of the British Society of Paediatric Dentistry (BSPD) and the European Academy of Paediatric Dentistry (EAPD), and their views on the use of minimal intervention dentistry (MID) in children prior to, during and post the COVID era.MethodsA total of 212 paediatric dentists and DwSI completed an online questionnaire. Six MID techniques were explored: fissure sealants, resin infiltration, Hall Technique (HT), 38% silver diamine fluoride (SDF), atraumatic restorative treatment (ART), stepwise removal and selective caries removal.ResultsThe majority were specialists (26%) followed by clinical academics (23.1%) working mainly in university teaching hospitals (46.2%). Routine dental treatment for children with carious primary teeth was provided by the majority (92.5%) during the pandemic. HT (96%) and 38% SDF (65.7%) were the most commonly used techniques among the BSPD members whereas conventional restoration of non-selective caries removal and pulp therapy remained the most widely used technique among the EAPD members (66.2%). Most of the MID techniques were used as a treatment option (48.1%) rather than a choice (43.4%), with most of these choices having been affected by the patient's behaviour (82.5%). More than one thirds (39.2%) of the participants were reluctant to adopt MID after the pandemic. Several barriers such as lack of teaching and confidence as well as perceived lack of evidence were identified.ConclusionA range of MID techniques is practiced broadly by a sample of paediatric dentists and DwSI across the United Kingdom (U.K) and European Union (E.U). The majority of clinicians are willing to continue using these techniques going forward after COVID restrictions are lifted. The pandemic served as an opportunity for many dentists to become familiar with various MID practices, such as SDF, which has been already established some time ago

The effect of premature extraction of primary teeth on the subsequent need for orthodontic treatment.

AIM: To investigate if premature extraction of primary teeth was associated with orthodontic need in the permanent dentition. STUDY DESIGN: This was a case-control study based on retrospective dental records. METHODS: As part of NHS (UK) Dental Epidemiology Programme a sample of 366, 12-year-old children from Bradford and Airedale were examined. The survey collected data on patient demographics, dental health status including orthodontic need. Data linkage was undertaken for those children participating in the NHS Dental Epidemiology Programme who had previously accessed the local Salaried Dental Service (SDS). For these children, retrospective dental information was collected about premature extraction of primary teeth. RESULTS: From the 366 children who were surveyed, 116 children had received treatment at the local SDS in the past. Significantly more children from ethnic minorities, low socioeconomic backgrounds and high caries rate (p < 0.001) were seen in the SDS. For the 107 children who attended SDS, an increased total number of primary teeth extractions was positively associated with orthodontic need (odds ratio:1.18, CI -1.01 to 1.37). STATISCTICS: Multilevel modelling was undertaken to identify variables associated with orthodontic need. CONCLUSIONS: In the study group, orthodontic need was significantly associated with the number of primary teeth extracted

Restorative management of the posterior tooth that has undergone a pulpotomy

Pulpotomy is increasingly being recognized as a treatment option for the management of permanent teeth with extremely deep caries. These teeth can present with or without symptoms of pulpitis. Traditionally, irreversible pulpitis has been managed with pulp extirpation and root canal treatment. Contemporary research has shown that pulpotomy may be suitable to manage permanent teeth diagnosed with irreversible pulpitis. This article discusses the options and decision-making process of how to restore posterior permanent teeth that have undergone a pulpotomy. In addition, the article highlights diagnostic and material considerations relating to the role of pulpotomy in managing deep caries. CPD/Clinical Relevance: Clinicians should be aware of the use of pulpotomy in management of extremely deep caries or partial irreversible pulpitis in permanent teeth. </jats:p

Exploring Constructive Solid Geometry for Building Reconstruction from Point Clouds: Preliminary Results

As-built BIM reconstruction supports building digitalization, enabling efficient management and maintenance of existing buildings. Manual reconstruction from point clouds is both error-prone and cost-intensive, while automatic reconstruction remains challenging despite recent advancements. This paper explores the use of Constructive Solid Geometry (CSG) for automatically reconstructing IFC-compatible models from indoor point clouds of existing buildings. The proposed approach starts with segmented point clouds corresponding to rooms, doors, and windows, then CSG operations are used to reconstruct key building components as solids, including slabs, walls, doors, windows, and interior spaces. These solids are subsequently converted into corresponding IFC entities. The method is evaluated using two case studies, achieving a centimetre-level accuracy and a runtime of approximately 9 seconds per case study. The proposed method provides a promising ability to advance the Scan-to-BIM pipeline, as it enables accurate reconstruction of building components while preserving topological relationships during an efficient runtime

Effect of indium doping on the electrical and structural properties of TiO2 thin films used in MOS devices

We investigated the effect of Indium (In) doping on the structural and electrical properties of Ti/Au/ TiO2:In/n-Si metal-oxide-semiconductor (MOS) devices. Sputtering grown TiO2 thin films on Si substrate were doped using two In-films with 15 nm and 50 nm thicknesses leading to two structures named Low Indium Doped (LID) sample and High Indium Doped (HID) sample, respectively. XRD analysis shows no diffraction pattern related to Indium indicating that In has been incorporated into the TiO2 lattice. Current-Voltage (I-V) characteristics show that rectification ratio at 2V is higher for HID sample than for LID sample. Evaluated barrier height, ϕB0 , decreased while the ideality factor, n, increased with decreasing temperature. Such behavior is ascribed to barrier inhomogeneity that was assumed to have a Gaussian Distribution (GD) of barrier heights at interface. Evidence of such GD was confirmed by plotting ϕB0versus n. High value of mean barrier ϕ̅B0 and lower value of standard deviation (σ) of HID structure are due to indium doping which increases the barrier homogeneities. Finally, estimated Richardson constants A* are in good agreement with theoretic values (112 A/cm2K2), particularly, for the HID structure

Growth of highly conductive Al-rich AlGaN:Si with low group-III vacancy concentration

Publisher Copyright: © 2021 Author(s).The impact of AlGaN growth conditions on AlGaN:Si resistivity and surface morphology has been investigated using metalorganic chemical vapor deposition. Growth parameters including growth temperature, growth rate, and trimethylindium (TMI) flow have been systematically studied to minimize the resistivity of AlGaN:Si. We observed a strong anticorrelation between AlGaN:Si conductivity and growth temperature, suggesting increased silicon donor compensation at elevated temperatures. Secondary ion mass spectrometry and positron annihilation spectroscopy ruled out compensation by common impurities or group-III monovacancies as a reason for the observed phenomenon, in contrast to theoretical predictions. The underlying reason for AlGaN:Si resistivity dependence on growth temperature is discussed based on the possibility of silicon acting as a DX center in Al0.65Ga0.35N at high growth temperatures. We also show remarkable enhancement of AlGaN:Si conductivity by introducing TMI flow during growth. A minimum resistivity of 7.5 m? cm was obtained for n-type Al0.65Ga0.35N, which is among the lowest reported resistivity for this composition.& nbsp;(c)& nbsp;2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(http://creativecommons.org/licenses/by/4.0/).& nbsp;Peer reviewe