Surface Defect Formation and Passivation in Formamidinium Lead Triiodide (FAPbI3) Perovskite Solar Cell Absorbers.

Formamidinium lead iodide based hybrid perovskite materials with improved efficiency and stability still lack well-understood surface defect formation mechanisms. Controlling the surface termination and defects has the potential to improve the performance of both conventional 3D and latterly reduced-dimensional perovskites photovoltaics. Here, we characterized the termination and all possible defect formations in FAPbI3 surface by the first-principles calculations. We found that, among the surfaces we considered, FAI-termination exhibits the most stable surface with a high defect tolerance. The PbI2-terminated surface is also found to be relatively stable; however, certain defects, such as electron-donating FA-interstitial and Pb-interstitial defects, can create deep-level stable charge-traps, potentially limiting the optoelectronic performance. We further investigate the surface treatment on these deep defects by model small molecule additives. We found that benzene additive with delocalized electron distribution can effectively passivate the deep FA-interstitial and Pb-interstitial defects by electron donating to the surface defect through charge-transfer.

Current-driven coherent skyrmion generation.

The next-generation logic and memory devices using magnetic skyrmions as spintronic information carriers are frequently studied, thanks to their remarkable magnetic stability, extremely compact size and very-low-cost driving forces within nanotracks. In order to realize skyrmion-based spintronic devices, understanding the skyrmion generation and their dynamics are essential. In this study, we have carried out a systematic micromagnetic simulation study on coherent magnetic skyrmion generation in which we theoretically engineered nanotracks by embedding an anti-notch to a channel of certain width. We found that the drift velocity and the skyrmion generation frequency can be tailored by the applied spin-polarized DC current density. Moreover, skyrmion generation is crucially affected by both damping and nonadiabaticity parameters, as well as the geometry of the anti-notch. We anticipate that our predictions provide rational basis for skyrmion-based devices in which skyrmions are used as information carriers, and influence future discussions.

Intrinsic charge-mobility in benzothieno[3,2-b][1]benzothiophene (BTBT) organic semiconductors is enhanced with long alkyl side-chains.

Recent measurements show that organic materials with a conjugated benzothieno-benzothiophene (BTBT) core exhibit unprecedented charge-carrier mobilities, dramatically influenced by the size of the side-chains. Using a multitude of computational tools, we, in depth, calculate the molecular ordering and charge-transport of these materials to rationalize the side-chain dependence. The reported experimental hole mobilities typically fall within the range of 1-100 cm2 V-1 s-1, therefore we employ both band transport models using deformation-potential theory based on DFT-D3 methodology and hopping transport using kinetic Monte Carlo simulations employing Marcus-Levich-Jortner charge-transfer theory. Band transport calculations are performed in a perfect lattice, considered as a structurally ordered morphology, while hopping transport calculations are performed for both ordered and disordered morphologies based on molecular dynamics simulations. We find that intrinsic mobility in BTBTs is critically controlled by the alkyl chain length; typically, longer alkyl side-chains regulate intrinsic disorder, cause improved balance between different transport directions and, ultimately, lead to enhanced charge-carrier mobility.

Prevalence of traumatic dental injuries and associated factors among 8 to 12-years-old schoolchildren in Diyarbakir, Turkey.

BACKGROUND AND OBJECTIVES: This study aimed to assess the prevalence of traumatic injuries of the permanent incisors in public primary schoolchildren from 8 to 12 years old in South-Eastern Anatolia, Turkey. Additionally, the relationship between traumatic dental injuries, parents' education level, family income, size of incisal overjet and the presence of anterior open bite were examined. MATERIALS AND METHODS: Data were collected through oral examinations and structured interviews, and included socio-economic indicators. A total of 2907 children of both genders (1498 boys, 1409 girls) were included in the study. The response rate was 97%. RESULTS: The prevalence of dental injuries was 4.6% (n = 135). The highest frequency of trauma in permanent teeth was observed at the age of 12 (8%). Boys experienced more dental injuries than girls, 5.9% and 3.3% (p = 0.001), respectively. The most commonly reported cause of injuries to the permanent incisors was falls (71.8%), followed by collision with objects or people (17.8%). Maxillary central incisors were the most affected by dental injuries (154, 84.6%). The most common crown fracture was in enamel only (67.58%) followed by crown fracture of enamel and dentin (22.52%). CONCLUSION: Socio-economic indicators and parents' level of education were not statistically significantly associated with the occurrence of traumatic dental injuries. Factors associated with increased risk of dental injuries in permanent teeth were age, gender, having an incisal overjet greater than 5mm and anterior open bite.

Dichotomy between the band and hopping transport in organic crystals: insights from experiments.

The molecular understanding of charge-transport in organic crystals has often been tangled with identifying the true dynamical origin. While in two distinct cases where complete delocalization and localization of charge-carriers are associated with band-like and hopping-like transports, respectively, their possible coalescence poses some mystery. Moreover, the existing models are still controversial at ambient temperatures. Here, we review the issues in charge-transport theories of organic materials and then provide an overview of prominent transport models. We explored ∼60 organic crystals, the single-crystal hole/electron mobilities of which have been predicted by band-like and hopping-like transport models, separately. Our comparative results show that at room-temperature neither of the models are exclusively capable of accurately predicting mobilities in a very broad range. Hopping-like models well-predict experimental mobilities around µ ∼ 1 cm2 V-1 s-1 but systematically diverge at high mobilities. Similarly, band-like models are good at µ > ∼50 cm2 V-1 s-1 but systematically diverge at lower mobilities. These results suggest the development of a unique and robust room-temperature transport model incorporating a mixture of these two extreme cases, whose relative importance is associated with their predominant regions. We deduce that while band models are beneficial for rationally designing high mobility organic-semiconductors, hopping models are good to elucidate the charge-transport of most organic-semiconductors.

A case of Beckwith-Wiedemann syndrome with peculiar dental findings.

BACKGROUND: Beckwith-Wiedemann syndrome (BWS, OMIM 130650) is a rare genetic disorder characterised by overgrowth, tumor predisposition and congenital malformations. Few systemic manifestations and oral features have been reported so far. CASE REPORT: We report on a case of BWS, describing all features expanding the knowledge on oro-dento-facial phenotypes, along with a review of the literature.

Effect of long term 900 MHz radiofrequency radiation on enamel microhardness of rat's teeth.

PURPOSE: Oral tissues are important parts of body that absorbs radiation emitted from mobile phones which is the most popular technological equipment in the world. Because of the limited studies in this field, we aimed to investigate the effect of Radio Frequency (RF) radiation emitted from 900 MHz mobile phones on the enamel micro hardness of rat teeth. MATERIALS AND METHODS: The study was carried out on twenty one Wistar Albino adult male rats which were divided into two groups such as control and experiment groups. For the study group (n: 14), rats exposed to the radiation 2 h per day (7 days in a week) for 10 months. For the control group (n: 7), rats were placed into the carousel and the same procedure was applied except that the generator was turned off. At the end of the study, enamel micro hardness of rat's teeth was measured. RESULTS: The results of this study showed that 900 MHz RF radiation did not alter the enamel micro hardness of rats' teeth (p>0.05). CONCLUSIONS: Exposure of 900 MHz RF radiation for 2 hours per day during ten months does not alter enamel micro hardness of rats' teeth. However, further studies are necessary to clarify this topic.

The reliability of microleakage studies using dog and bovine primary teeth instead of human primary teeth.

AIM: This was to investigate if dental restorations on human, dog and bovine primary teeth are equitable for microleakage analysis, and the respective marginal adaptation deficiency in in vitro conditions. MATERIALS AND METHODS: In order to determine the level of microleakage in Class V poly acid-modified composite restorations of human, dog and bovine primary teeth, samples were evaluated by dye-leakage method in sections of the inner area of the restorations. RESULTS: We found no leakage in 6 out of 10 (60%) human restorations, in 7 out of 10 (70%) of dog and in 7 out of 10 (70%) of bovine teeth. The levels of dye-microleakage were tested with Kruskal-Wallis one-way variant analysis method. The relative leakage differences were not statistically significant among all species (p>0.05). CONCLUSION: We concluded that dog and bovine primary teeth might be suitable for in vitro studies instead of human ones.

Effect of extremely low frequency magnetic field on enamel microhardness in rats.

AIM: The potential effects on human health of extremely low frequency magnetic field (ELF-MF) are of considerable concern. In the present study, it was investigated the effect of long term ELF-MF exposure on microhardness of rat teeth. MATERIALS AND METHODS: Thirty male Sprague-Dawley rats were divided into three groups. The first and second experimental groups (n=10) were exposed to 100 µT and 500 µT ELF-MF during 10 months, 2 hours a day respectively. For the control group, nothing was applied to the rats and they completed their life cycle in the cage during the study period. After ELF-MF exposure, microhardness of enamel surface was determined for each group. RESULTS: The decrease in microhardness in the second experimental group was found to be statistically significant compared to the control group (P <0.05). However, no statistical difference was found between the first and second experimental groups (P >0.05). CONCLUSION: From the results it can be concluded that 500 µT level of magnetic field strengths may have a certain negative effect on enamel mineralisation. Further investigations are necessary to analyse the effect of ELF-MF on teeth.

Incisor trauma in a Turkish preschool population: prevalence and socio-economic risk factors.

OBJECTIVE: This study aimed to assess the prevalence of traumatic injuries of the primary incisors in preschool children from 2 to 5 years old in South-Eastern Anatolia, Turkey. Additionally, the relationship between traumatic dental injuries, parents' education level, family income, size of incisal overjet and the presence of anterior open bite were examined. BASIC RESEARCH DESIGN: A cross-sectional survey CLINICAL SETTINGS: Data were collected through oral examinations and structured interviews, and included socio-economic indicators. PARTICIPANTS: A total of 727 children of both genders were included in the study. 122 of these children were aged 2; 183 aged 3; 178 aged 4 and 186 aged 5. RESULTS: The prevalence of dental injuries was 8.0% (n = 58). The highest frequency of trauma in the primary teeth was observed at the age of 4. Boys experienced more dental injuries than girls, 12.2% and 4.0%, respectively. The most common crown fracture was in enamel only (57%) followed by crown fracture of enamel and dentin (19%). CONCLUSION: The prevalence of dental injuries in Turkish preschool children was very low. The children with incisal overjet greater than 5mm and anterior open bite experienced more dental injuries in primary teeth than their counterparts with normal occlusion. Socio-economic indicators were not statistically significantly associated with the occurrence of traumatic dental injuries.

Importance of urinary measurement of glutathione S-transferase in renal dysfunction patients after on- and off-pump coronary artery bypass surgery.

BACKGROUND: Acute renal failure (ARF) occurring after on-pump and off-pump cardiac surgery was assessed by urinary alpha glutathione S-transferase measurement (alpha-GST) in patients who already had renal dysfunction. METHODS: Fifty-one patients with plasma creatinine levels ranging between 1.5 and 2.0 mg/dL were included in the study. On-pump coronary artery bypass was performed in 25 of them, and off-pump surgery in the other 25 patients. Urinary alpha-GST levels, plasma creatinine levels, creatinine clearance and fractional excretion of sodium were measured. RESULTS: Urinary alpha-GST levels were found to be significantly increased at 24 hours postoperatively. A weak correlation was detected between alpha-GST levels and plasma creatinine, creatinine clearance and fractional excretion of sodium. Preoperative and postoperative 24 hour levels showed a positive predictive value for the occurrence of acute renal failure. CONCLUSIONS: Tubular damage produced by cardiopulmonary bypass is not the only factor associated with postoperative ARF. Because factors independent of pump usage can adversely affect renal function, excluding pump usage alone is not sufficient to prevent postoperative ARF in patients who have preoperative renal dysfunction.

Craniofacial and upper airway cephalometrics in hypohidrotic ectodermal dysplasia.

OBJECTIVES: The aim of this study was to evaluate the craniofacial and upper airway structures in patients with hypohidrotic ectodermal dysplasia (HED). SUBJECTS AND METHODS: Craniofacial and upper airway dimensions were measured on lateral cephalometric radiographs of ten HED patients (four females and six males) and ten normal class III patients as a control group. 21 dimensional measurements were used for cephalometric assessment. Craniofacial structures were compared with normal values and airway dimensions were compared with those of a control group with a similar skeletal pattern. RESULTS: We found that the SNA degrees, SNB degrees, ANB degrees, SN-GoMe degrees and the distance between the lips and the S-line were lower than those in normal subjects, while soft tissue convexity angles were higher in HED patients. Statistically significant decreases occurred in tongue length, vertical airway length, hyoid bone mandibular plane length, hyoid bone C3 length, middle airway space and inferior airway space, while the soft palate length increased. CONCLUSIONS: The characteristic craniofacial features of HED patients are class III malocclusion with maxillary retrusion and deficiency in vertical, transversal and sagittal growth of the jaw and soft tissues. HED patients have smaller pharyngeal and upper airway dimensions, and the hyoid bone is positioned more posteriorly compared with class III control individuals.

Effect of a chronic nail-biting habit on the oral carriage of Enterobacteriaceae.

BACKGROUND/AIMS: Nail biting is a common oral habit in children and young adults. However, its effect on the oral carriage of Enterobacteriaceae is unclear. The purpose of the study was to evaluate the differences in prevalence of Enterobacteriaceae in saliva samples from subjects with and without a nail-biting habit. METHODS: Saliva samples were taken from 25 subjects who were nail-biters and 34 subjects with no oral habit. The mean chronological age for all subjects was 13.5 +/- 1.9 years. The saliva samples were studied microbiologically. A Pearson chi-squared test was performed to compare the prevalence of Enterobacteriaceae in the saliva samples of the subjects with and without nail-biting habits. RESULTS: Statistically significant differences were found in the prevalence of Escherichia coli and total Enterobacteriaceae between both groups (P < 0.001). E. coli, Enterobacter aerogenes, Enterobacter cloacae and Enterobacter gergoviae were found in the saliva samples of 19 of the 25 nail-biting subjects (76%), whereas E. coli, E. aerogenes and E. cloacae were detected in the saliva samples of only nine of the 34 subjects who were not nail-biters (26.5%). CONCLUSION: According to the results of the present study, the Enterobacteriaceae were more prevalent in the oral cavities of children with nail-biting habits than in children with no oral habit.

Open surgical approach for a tooth aspirated during dental extraction: a case report.

Foreign body aspiration is a common problem in children necessitating prompt recognition and early treatment to minimize the potentially serious and sometimes even fatal consequences. Most foreign bodies can usually be extracted by skilful application of endoscopic techniques. Nevertheless, spherical foreign bodies, such as pen caps and some teeth remain difficult to manage. In this case report clinical presentation and treatment options in the treatment of a patient who had a tooth lodged in the right lung are discussed. The complications of foreign body ingestion or aspiration associated with dental treatment is emphasized.

Serum levels of insulin-like growth factor-I and insulin-like growth factor binding protein-3 in children with insulin-dependent diabetes mellitus.

Pubertal development has recently been evaluated from the standpoint of changes in insulin-like growth factor (IGF)-I and IGF-binding protein-3 (IGFBP-3) levels in healthy children. We studied puberty related changes in serum IGF-I and IGFBP-3 levels in 24 patients (11 prepubertal) with insulin dependent diabetes mellitus (IDDM) and 26 healthy subjects (14 prepubertal). Serum IGF-I and IGFBP-3 levels were assayed using immunoradiometric assays and radioimmunoassays, respectively. Serum IGF-I and IGFBP-3 levels in diabetics did not increase during puberty, as opposed to those in healthy children. Serum IGF-I and IGFBP-3 levels of diabetic patients were found to be lower than those of control subjects during puberty (p < 0.0001 and p < 0.05, respectively). Proteolysis is believed to be a general mechanism to increase IGF bioavailability in the presence of IGFBPs. Increased IGFBP-3 protease activity has been shown in sera of children with IDDM as well as a decrease in this activity in response to insulin therapy. Our data displaying low IGFBP-3 levels in diabetic children may be due to increased proteolysis, which also causes a shift in IGF-I to its lower molecular weight forms. Higher rate of clearance of the latter may be the reason for the low IGF-I levels we observed in children with IDDM. The moderate correlation between insulin dose and IGFBP-3 levels (r = 0.5, p < 0.01) may suggest insulin to be a contributing factor in the regulation of IGFBP-3 levels. We conclude that regulation of IGF-I and IGFBP-3 concentrations is disturbed in children with IDDM, in particular during adolescence.

Serum and cerebrospinal fluid zinc levels in children with febrile convulsions.

The mechanisms underlying febrile convulsions (FC), which have multiple etiological factors, are not yet clear. The aim of the present study was to determine whether there were any changes in serum and cerebrospinal fluid (CSF) zinc (Zn) levels in children with febrile convulsion during seizures. A total of 102 children were included in the study, with four groups formed as follows: group A, 40 children with FC (aged 9 months to 5 years); group B. 20 children having fever without convulsion (aged 6 months to 5 years); group C, 20 children with afebrile convulsion (aged 6 months to 6 years) and group D, 22 healthy children (aged 5 months to 6 years). Serum and CSF zinc levels for groups A, B and C and serum Zn levels only for group D were measured. The serum Zn levels of 17 children in group A were again measured during healthy periods. Serum Zn levels of groups A, B, C and D had a mean of 0.70 +/- 0.10 mg/dL, 1.07 +/- 0.08 mg/dL. 1.26 +/- 0.32 mg/dL and 1.17 +/- 0.21 mg/dL, respectively, and the values of group A were lower than those of the other three groups (P < 0.001). In group B, serum Zn levels were also lower than those of groups C and D (P < 0.05). The CSF Zn levels of groups A, B and C were found to have a mean of 0.07 +/- 0.02 mg/L, 0.12 +/- 0.02 mg/L and 0.14 +/- 0.04 mg/L, respectively. In group A, the CSF Zn levels were lower than those of groups B and C (P < 0.001), and in group B they were lower than those of group C (P < 0.05). For the 17 patients in group A, serum Zn levels during healthy periods (0.87 +/- 0.10 mg/dL) were found to be higher than the values shortly after seizures, but lower than those of groups B, C and D (P < 0.001). We could not observe any relationship between zinc levels of the serum and CSF and the degree and duration of the fever. These findings suggest that serum and CSF Zn levels decreased during infectious diseases, and that this decrease was more significant in patients with FC.