Electrostatically tunable interaction of CO2 with MgO surfaces and chemical switching: first-principles theory.

Electric field-assisted CO2 capture using solid adsorbents based on basic oxides can immensely reduce the required energy consumption compared to the conventional processes of temperature or pressure swing adsorption. In this work, we present first-principles density functional theoretical calculations to investigate the effects of an applied external electric field (AEEF) within the range from -1 to 1 V Å-1 on the CO2 adsorption behavior on various high and low-index facets of MgO. When CO2 is strongly adsorbed on MgO surfaces to form carbonate species, the coupling of electric fields with the resulting intrinsic dipole moment induces a 'switch' from a strongly chemisorbed state to a weakly chemisorbed or physisorbed state at a critical value of AEEF. We demonstrate that such 'switching' enables access to different metastable states with variations in the AEEF. On polar MgO(111) surfaces, we find a distinct feature of the adsorptive dissociation of CO2 towards the formation of CO in contrast to that on the non-polar MgO(100) and MgO(110) surfaces. In some cases, we observe broken inversion symmetry because of the AEEF that results in induced polarity at the interaction site of CO2 on MgO surfaces. Our results provide fundamental insights into the possibility of using AEEFs in novel solid adsorbent systems for CO2 capture and reduction.

Activation of CO2 and CH4 on MgO surfaces: mechanistic insights from first-principles theory.

One of the most challenging topics in heterogeneous catalysis is conversion of CH4 to higher hydrocarbons. Direct conversion of CH4 to ethylene can be achieved via the oxidative coupling of methane (OCM) reaction. Despite studies which have shown MgO to activate CH4 and initiate the OCM reaction, its large-scale applications face a significant impediment due to formation of a byproduct, CO2, and poisoning of the catalyst due to carbonate formation. In the present work, we address two aspects of the OCM reaction on MgO surfaces: carbonate formation on the surface of the catalyst, and (dissociative) adsorption of CH4. We use first-principles density functional theoretical calculations to determine the energetics and underlying mechanisms of interaction of CO2 and CH4 with various surfaces of MgO: (100), (110), and (111) (both Mg- and O-terminations), and the seldom studied, hydroxylated (111) MgO surface with O-termination. We find that the strength of the interaction of CO2 with MgO surfaces depends on several factors: their surface energies, coordination number of surface O atoms, and ability to donate electrons. However, the O-terminated (111) surface of MgO bucks all aforementioned factors, with only oxygen richness affecting its reactivity towards CO2. The interaction of CH4 with MgO surfaces depends primarily on the coordination number of the surface O atoms and the orientation of the CH4 molecule with respect to the surface. Finally, we provide insights into (a) formation of surface carbonates, which is relevant to CO2 capture and conversion, and (b) C-H bond activation on MgO surfaces, which is crucial for direct conversion of CH4 to value-added chemicals.

Monodentate Phosphinoamine Nickel Complex Supported on a Metal-Organic Framework for High-Performance Ethylene Dimerization.

Ethylene dimerization is an efficient industrial chemical process to produce 1-butene, with demanding selectivity and activity requirements on new catalytic systems. Herein, a series of monodentate phosphinoamine-nickel complexes immobilized on UiO-66 are described for ethylene dimerization. These catalysts display extensive molecular tunability of the ligand similar to organometallic catalysis, while maintaining the high stability attributed to the metal-organic framework (MOF) scaffold. The highly flexible postsynthetic modification method enables this study to prepare MOFs functionalized with five different substituted phosphines and 3 N-containing ligands and identify the optimal catalyst UiO-66-L5-NiCl2 with isopropyl substituted nickel mono-phosphinoamine complex. This catalyst shows a remarkable activity and selectivity with a TOF of 29 000 (molethyl/molNi/h) and 99% selectivity for 1-butene under ethylene pressure of 15 bar. The catalyst is also applicable for continuous production in the packed column micro-reactor with a TON of 72 000 (molethyl/molNi). The mechanistic insight for the ethylene oligomerization has been examined by density functional theory (DFT) calculations. The calculated energy profiles for homogeneous complexes and truncated MOF models reveal varying rate-determining step as ß-hydrogen elimination and migratory insertion, respectively. The activation barrier of UiO-66-L5-NiCl2 is lower than other systems, possibly due to the restriction effect caused by clusters and ligands. A comprehensive analysis of the structural parameters of catalysts shows that the cone angle as steric descriptor and butene desorption energy as thermodynamic descriptor can be applied to estimate the reactivity turnover frequency (TOF) with the optimum for UiO-66-L5-NiCl2. This work represents the systematic optimization of ligand effect through combination of experimental and theoretical data and presents a proof-of-concept for ethylene dimerization catalyst through simple heterogenization of organometallic catalyst on MOF.

Expression of syndecan-1 in different grades of oral squamous cell carcinoma: An immunohistochemical study.

Background: Syndecans are a family of transmembrane proteins, belonging to heparin sulphate proteoglycan family and are localized entirely to the epithelial cells with the stratified squamous epithelia. They are involved in cell-cell adhesion and interaction with the extracellular matrix and play a critical role in cell growth, differentiation, cell morphology, and migration. The down regulation of syndecan-1 indicates loss of cellular adhesion and possibility of invasion. The present study is aimed to evaluate the difference in immunohistochemical expression of syndecan-1 in different grades of oral squamous cell carcinoma (OSCC) patients and control group. Methods: The present study consists of 42 cases of paraffin-embedded tissue sections of OSCC; 14 well differentiated, 14 moderately differentiated, and 14 poorly differentiated. As a control, 10 paraffin-embedded tissue sections of unaffected oral mucosa were used. The sections were stained for immunohistochemical expression of syndecan -1. The intensity of staining was scored. The immunohistochemistry scores for each sample were obtained by Tissue Quant software. Results: Statistical analysis revealed that there was a significant decrease in intensity of staining between normal and different grades of OSCC. Conclusion: This study shows that as cellular differentiation was lost, syndecan-1 expression was less. This provides an insight and understanding of the pathophysiology of the invasive process of OSCC and helps in establishing the prognostic link.

Assessment of the role of the Edinburgh dysphagia score in referral triage in a national service evaluation of the urgent suspected upper gastrointestinal cancer pathway.

BACKGROUND: The British Society of Gastroenterology has recommended the Edinburgh Dysphagia Score (EDS) to risk-stratify dysphagia referrals during the endoscopy COVID recovery phase. AIMS: External validation of the diagnostic accuracy of EDS and exploration of potential changes to improve its diagnostic performance. METHODS: A prospective multicentre study of consecutive patients referred with dysphagia on an urgent suspected upper gastrointestinal (UGI) cancer pathway between May 2020 and February 2021. The sensitivity and negative predictive value (NPV) of EDS were calculated. Variables associated with UGI cancer were identified by forward stepwise logistic regression and a modified Cancer Dysphagia Score (CDS) developed. RESULTS: 1301 patients were included from 19 endoscopy providers; 43% male; median age 62 (IQR 51-73) years. 91 (7%) UGI cancers were diagnosed, including 80 oesophageal, 10 gastric and one duodenal cancer. An EDS ≥3.5 had a sensitivity of 96.7 (95% CI 90.7-99.3)% and an NPV of 99.3 (97.8-99.8)%. Age, male sex, progressive dysphagia and unintentional weight loss >3 kg were positively associated and acid reflux and localisation to the neck were negatively associated with UGI cancer. Dysphagia duration <6 months utilised in EDS was replaced with progressive dysphagia in CDS. CDS ≥5.5 had a sensitivity of 97.8 (92.3-99.7)% and NPV of 99.5 (98.1-99.9)%. Area under receiver operating curve was 0.83 for CDS, compared to 0.81 for EDS. CONCLUSIONS: In a national cohort, the EDS has high sensitivity and NPV as a triage tool for UGI cancer. The CDS offers even higher diagnostic accuracy. The EDS or CDS should be incorporated into the urgent suspected UGI cancer pathway.

Focal active colitis: a prospective study of clinicopathological correlations in 90 patients.

AIMS: Considerable controversy exists about the clinical implication of a diagnosis of focal active colitis (FAC). The aim of this study was to assess clinicopathological correlations of FAC in 90 adults, representing the largest and only prospective series of FAC. METHODS AND RESULTS: Patients were assessed by comprehensive clinical follow-up and questionnaires. Fifteen histopathological features were scored and correlated with clinical outcome. In 24% of patients drugs, especially NSAIDs, were implicated. Infection was a probable cause in 19%. In 14 patients (15.6%), predominantly women, a diagnosis of chronic inflammatory bowel disease was ultimately made. Most were Crohn's disease, but this is the first study in which FAC has presaged an ultimate diagnosis of ulcerative colitis in adults (in two patients). A specific subtype of FAC, termed basal FAC, was significantly associated with drugs. These excepted, this study has found no histopathological parameters of FAC, such as amount, location and/or distribution, to correlate with clinical outcome or allowed selection of those patients more likely to show subsequent evidence of chronic inflammatory bowel disease. CONCLUSION: This study has provided powerful information on the implication of a diagnosis of FAC. In a small but not inconsiderable case number, the ultimate diagnosis will be chronic inflammatory bowel disease.

Insights into Coke Formation and Removal under Operating Conditions with a Quantum Nanoreactor Approach.

The in situ formation and removal of coke is a critical problem in heterogeneous catalysis, but its mechanism is not well understood. This work investigates the mechanism of carbon deposition and hydrogenation on an Fe cluster under high-temperature conditions with the density functional tight-binding (DFTB) based nanoreactor molecular dynamics (NMD) method. Our study shows that successive formation of carbon chains, rings, and fused rings occurred during the carbon deposition on Fe clusters. Hydrogenation of activated carbon happens through direct C-H coupling, while the hydrogenation of graphitic carbon involves hydrogenation of the edge carbon, ring-opening reaction, and dealkylation reaction. The main function of the Fe catalyst is to provide the active sites for H2 dissociation and dissociated H spillover, while its activity toward C-C bond breaking is limited. These results highlight the role of the DFTB-NMD method as an effective tool to investigate reaction mechanisms under operating conditions in heterogeneous catalysis.

Evaluating the Viability of a Smartphone-Based Annotation Tool for Faster and Accurate Image Labelling for Artificial Intelligence in Diabetic Retinopathy.

INTRODUCTION: Deep Learning (DL) and Artificial Intelligence (AI) have become widespread due to the advanced technologies and availability of digital data. Supervised learning algorithms have shown human-level performance or even better and are better feature extractor-quantifier than unsupervised learning algorithms. To get huge dataset with good quality control, there is a need of an annotation tool with a customizable feature set. This paper evaluates the viability of having an in house annotation tool which works on a smartphone and can be used in a healthcare setting. METHODS: We developed a smartphone-based grading system to help researchers in grading multiple retinal fundi. The process consisted of designing the flow of user interface (UI) keeping in view feedback from experts. Quantitative and qualitative analysis of change in speed of a grader over time and feature usage statistics was done. The dataset size was approximately 16,000 images with adjudicated labels by a minimum of 2 doctors. Results for an AI model trained on the images graded using this tool and its validation over some public datasets were prepared. RESULTS: We created a DL model and analysed its performance for a binary referrable DR Classification task, whether a retinal image has Referrable DR or not. A total of 32 doctors used the tool for minimum of 20 images each. Data analytics suggested significant portability and flexibility of the tool. Grader variability for images was in favour of agreement on images annotated. Number of images used to assess agreement is 550. Mean of 75.9% was seen in agreement. CONCLUSION: Our aim was to make Annotation of Medical imaging easier and to minimize time taken for annotations without quality degradation. The user feedback and feature usage statistics confirm our hypotheses of incorporation of brightness and contrast variations, green channels and zooming add-ons in correlation to certain disease types. Simulation of multiple review cycles and establishing quality control can boost the accuracy of AI models even further. Although our study aims at developing an annotation tool for diagnosing and classifying diabetic retinopathy fundus images but same concept can be used for fundus images of other ocular diseases as well as other streams of medical science such as radiology where image-based diagnostic applications are utilised.

Hydrogen induced CO activation on open Ru and Co surfaces.

An optimum reaction path for CO activation is an important issue in the Fischer-Tropsch synthesis for the production of liquid hydrocarbons from syngas. In the present theoretical study, we show that the CO activation on open Ru and Co surfaces consisting of active six-fold sites is initiated through the carbide mechanism instead of the hydrogen assisted pathway.

Direct versus hydrogen-assisted CO dissociation.

The mechanism of CO dissociation is a fundamental issue in the technologically important Fischer-Tropsch (F-T) process that converts synthesis gas into liquid hydrocarbons. In the present study, we propose that on a corrugated Ru surface consisting of active sixfold (i.e., fourfold + twofold) sites, direct CO dissociation has a substantially lower barrier than the hydrogen-assisted paths (i.e., via HCO or COH intermediates). This proves that the F-T process on corrugated Ru surfaces and nanoparticles with active sixfold sites initiates through direct CO dissociation instead of hydrogenated intermediates.

A comparative study of structural, acidic and hydrophilic properties of Sn-BEA with Ti-BEA using periodic density functional theory.

Periodic density functional theory has been employed to characterize the differences in the structural, Lewis acidic and hydrophilic properties of Sn-BEA and Ti-BEA. We show that the incorporation of Sn increases the Lewis acidity of BEA compared to the incorporation of Ti. Hence, the present work gives insight into the role of Sn in increasing the efficiency of the oxidation reactions. The results also justify that the percentage of Sn substituted in BEA is less than Ti. The structural analysis shows that the first coordination shell of Sn is larger than that of Ti. However, the second coordination of both sites remains the same. The water adsorption properties of these substituted zeolites are quantified. Moreover, we explain the higher Lewis acidity of Sn than the Ti site on the basis of the Fukui functions and charge population analysis.

Optical coherence tomography: A guide to interpretation of common macular diseases.

Optical coherence tomography is a quick, non invasive and reproducible imaging tool for macular lesions and has become an essential part of retina practice. This review address the common protocols for imaging the macula, basics of image interpretation, features of common macular disorders with clues to differentiate mimickers and an introduction to choroidal imaging . It includes case examples and also a practical algorithm for interpretation.

Evaluation of magnesium levels in blood and saliva of oral squamous cell carcinoma and potentially malignant disorders by xylidyl blue method.

BACKGROUND: Cancer is Latinized from Greek word 'karkinos' meaning crab, denoting how carcinoma extends its claws like a crab into adjacent tissues. It has been well established by researchers that virtually all oral cancer are preceded by visible clinical changes in the oral mucosa usually in the form of white or red patch (two-step process of cancer development). Mg is an essential mineral that is needed for a broad variety of physiological functions. Imbalances in Mg metabolism are common and are associated with different pathological conditions. The purpose of this study was to evaluate and compare the magnesium concentration in blood serum and saliva of oral squamous cell carcinoma, potentially malignant disorders and healthy subjects to serve as a positive marker or indicator in the process of carcinogenesis. MATERIALS AND METHODS: The study includes 17 precancerous (OSMF + Leukoplakia) patients, 17 OSCC and 17 control group. Blood and saliva was collected; serum and saliva was extracted from both the groups and was biochemically evaluated for magnesium levels. Statistical analysis was performed using ANOVA. RESULTS: The Salivary magnesium Mean ± SD of Healthy group is higher 1.6681 ± 0.0207 mmol mg/l followed by Potentially Malignant Disorder group 1.5532 ± 0.0283 and Oral Squamous Cell Carcinoma 0.5979 ± 0.0659. The mean values differ significantly between 3 groups (P < 0.001) The Serum magnesium Mean ± SD of Healthy group is higher 1.9188 ± 0.0550 mmol mg/l followed by Potentially Malignant Disorder group 1.6951 ± 0.0949 and Oral Squamous Cell Carcinoma 0.7329 ± 0.1561. The mean values differ significantly between 3 groups (P < 0.001) The study revealed decreased serum and salivary magnesium in oral precancerous patients and an Oral Squamous cell carcinoma patients compared to healthy individuals. CONCLUSION: The magnesium concentration was low in both blood plasma and saliva of oral squamous cell carcinoma as compared to potentially malignant disorders and healthy subjects. Thus the magnesium ion concentration in blood plasma and saliva could be considerd as tumor marker, playing an important role in carcinogenesis.

Does the presence of a trainee compromise success of biliary cannulation at ERCP?

BACKGROUND AND STUDY AIMS: Findings in the literature are conflicting on whether trainee involvement in endoscopic retrograde cholangiopancreatography (ERCP) procedures is detrimental to cannulation success rates. We addressed this in a prospective study, where cannulation success with or without trainee presence was the primary outcome measure. PATIENTS AND METHODS: We prospectively recorded data on 2 senior endoscopists and their trainees over an 18-month period for ERCPs in patients with a virgin ampulla. Presence or absence of a trainee at ERCP procedures was pragmatic, reflecting their other service or training commitments or annual leave. For trainee presence, the training protocol allowed them 6 minutes of supervised time in which to achieve biliary cannulation after reaching the ampulla. Study outcome measures included cannulation success, time to cannulation, technique, whether this was achieved independently by the trainee, and complications. RESULTS: There were 219 procedures recorded and analyzed (134 with a trainee, 85 without). Three trainees were involved. Selective biliary cannulation was achieved in 201 (92 %) of cases. When a trainee was present, cannulation was successful in 122/134 procedures (91 %), compared to 79/85 (93 %) with a senior endoscopist alone ( P  = 0.8, Fisher's exact test). Mean time to biliary cannulation with a trainee present was 7 minutes, compared with 5 minutes with no trainee. Mean time for successful independent cannulation by the trainee was 4 minutes, and 9 minutes for a consultant following a trainee's attempt. There were no serious adverse events. CONCLUSION: Our study shows that with this training protocol, involvement of a trainee on a routine secondary care ERCP list does not impair biliary cannulation success, and does not prolong a subsequent attempt by the senior endoscopist if initially unsuccessful. These findings support the involvement of trainees in routine ERCP lists with this training protocol.

Comparative evaluation of effect of use of toothbrush with paste and munident on levels of Streptococcus mutans and gingival health in children: An in vivo study.

AIM: Dental caries is a multifactorial disease which has a deleterious effect on the oral cavity. Improper oral hygiene habits are a cause for the same. The aim of this study was to compare the antibacterial efficacy of Munident, an Ayurvedic (herbal) dentifrice with commercially available toothpaste. MATERIALS AND METHODS: A total of forty subjects between the age group 9 and 12 years, resident of Bala Yeshu Nilaya Bhavan, Mangalore, Karnataka, India, were chosen for our study. They were divided into two groups containing twenty subjects in each; Group 1 for standard toothpaste and Group 2 for Munident. The decayed, missing, and filled teeth scores were noted from each subject. Group 1 was instructed to brush the teeth using commercially available toothpaste and Group 2 was instructed to brush using commercially available Munident (herbal) dentifrice. Both the groups brushed the teeth using soft variety of tooth brush. The gingival bleeding index and salivary Streptococcus mutans count were noted pre- and post-brushimg for both groups. The results obtained were subjected to statistical analysis. RESULTS: Munident (herbal) dentifrice showed better efficacy in comparison to toothpaste in terms of gingival bleeding index and salivary S. mutans count. CONCLUSION: Munident (herbal) dentifrice has better gingival bleeding index compared to standard formulation of toothpaste. Hence, the practice of using herbal dentifrice should be encouraged.

Development and Validation of a Diabetic Retinopathy Referral Algorithm Based on Single-Field Fundus Photography.

PURPOSE: To develop a simplified algorithm to identify and refer diabetic retinopathy (DR) from single-field retinal images specifically for sight-threatening diabetic retinopathy for appropriate care (ii) to determine the agreement and diagnostic accuracy of the algorithm as a pilot study among optometrists versus "gold standard" (retinal specialist grading). METHODS: The severity of DR was scored based on colour photo using a colour coded algorithm, which included the lesions of DR and number of quadrants involved. A total of 99 participants underwent training followed by evaluation. Data of the 99 participants were analyzed. Fifty posterior pole 45 degree retinal images with all stages of DR were presented. Kappa scores (κ), areas under the receiver operating characteristic curves (AUCs), sensitivity and specificity were determined, with further comparison between working optometrists and optometry students. RESULTS: Mean age of the participants was 22 years (range: 19-43 years), 87% being women. Participants correctly identified 91.5% images that required immediate referral (κ) = 0.696), 62.5% of images as requiring review after 6 months (κ = 0.462), and 51.2% of those requiring review after 1 year (κ = 0.532). The sensitivity and specificity of the optometrists were 91% and 78% for immediate referral, 62% and 84% for review after 6 months, and 51% and 95% for review after 1 year, respectively. The AUC was the highest (0.855) for immediate referral, second highest (0.824) for review after 1 year, and 0.727 for review after 6 months criteria. Optometry students performed better than the working optometrists for all grades of referral. CONCLUSIONS: The diabetic retinopathy algorithm assessed in this work is a simple and a fairly accurate method for appropriate referral based on single-field 45 degree posterior pole retinal images.

Unusual Case of Vogt-Koyanagi-Harada Syndrome Presenting as Non-specific Headache.

Vogt-Koyanagi-Harada syndrome (VKH) is a bilateral intraocular granulomatous panuveitis which is frequently associated with systemic manifestations such as meningismus, tinnitus, poliosis and vitiligo of autoimmune aetiology. Headache by itself, does not fulfill the diagnostic criteria and is insufficient for the diagnosis. A 22-year-old male presented with a 10 day history of headache, followed by decreased vision in both eyes. Slit lamp biomicroscopy revealed sluggishly reactive pupils with anterior uveitis, mild vitritis and hyperaemic discs with bilateral exudative retinal detachments. All uveitis workups were negative. Follow up of three years revealed no neurological or auditory symptoms. Headache alone, followed by decreased vision, before the onset of neurological and auditory symptoms, can be an initial presentation of Vogt-Koyanagi-Harada (VKH) syndrome. VKH should be considered in the differential diagnosis of atypical presentations of headache.

Comparative analysis of cell proliferation ratio in plaque and erosive oral lichen planus: An immunohistochemical study.

BACKGROUND: Proliferating cell nuclear antigen (PCNA) is a nuclear protein synthesized in the late G1 and S-phase of the cell cycle. Detection of this protein represents a useful marker of the proliferation status of lesions. This study has been carried out to evaluate the cell proliferation rate in oral lichen planus (OLP) and comparison between plaque and erosive lichen planus, which indicates the potential for malignant transformation. MATERIALS AND METHODS: This study was comprised of 64 cases of histologically proven lichen planus, out of which 32 cases of plaque and erosive each was taken. Two sections were taken from each, one for H and E staining to verify histological diagnosis according to Eisenberg criteria, other sections were stained according to super sensitive polymer horse radish peroxidise method for identifying immunohistochemical expression of PCNA. Data were statistically analyzed by Tukey high-range statistical domain test. Statistically significant P value was considered <0.05. RESULTS: In two types of lichen planus, erosive type (66.86%) showed higher expression of PCNA followed by plaque (17.07%). Overall, P value was <0.001, which was statistically significant. It indicates that proliferation activity is more in erosive lichen planus followed by plaque type, which ultimately results in increased rate of malignant transformation. CONCLUSION: PCNA is a good nuclear protein marker to evaluate the proliferation status of OLP. Out of the two types of lichen planus, erosive type possesses more proliferative ratio and chances of malignant change is more in this type. It emphasizes the importance of long-term follow-up with erosive type when compared with plaque type.