Enumerating Stable Nanopores in Graphene and their Geometrical Properties Using the Combinatorics of Hexagonal Lattices

Nanopores in two-dimensional (2D) materials, including graphene, can be used for a variety of applications, such as gas separations, water desalination, and DNA sequencing. So far, however, all plausible isomeric shapes of graphene nanopores have not been enumerated. Instead, a probabilistic approach has been followed to predict nanopore shapes in 2D materials, due to the exponential increase in the number of nanopores as the size of the vacancy increases. For example, there are 12 possible isomers when N=6 atoms are removed, a number that theoretically increases to 11.7 million when N=20 atoms are removed from the graphene lattice. The development of a smaller, exhaustive dataset of stable nanopore shapes can help future experimental and theoretical studies focused on using nanoporous 2D materials in various applications. In this work, we use the theory of 2D triangular "lattice animals" to create a library of all stable graphene nanopore shapes based on a modification of a well-known algorithm in the mathematical combinatorics of polyforms known as Redelmeier's algorithm. We show that there exists a correspondence between graphene nanopores and triangular polyforms (called polyiamonds) as well as hexagonal polyforms (called polyhexes). We develop the concept of a polyiamond ID to identify unique nanopore isomers. We also use concepts from polyiamond and polyhex geometry to eliminate unstable nanopores containing dangling atoms, bonds, and moieties. The exclusion of such unstable nanopores leads to a remarkable reduction in the possible nanopores from 11.7 million for N=20 to only 0.184 million nanopores, thereby indicating that the number of stable nanopores is almost two orders of magnitude lower and is much more tractable. Not only that, by extracting the polyhex outline, our algorithm allows searching for nanopores with dimensions and shape factors in a specified range.Comment: 27 pages and 12 figures in the main text, 6 pages and 5 figures in the supporting informatio

Incorporating Ion-Specific van der Waals and Soft Repulsive Interactions in the Poisson-Boltzmann Theory of Electrical Double Layers

Electrical double layers (EDLs) arise when an electrolyte is in contact with a charged surface, and are encountered in several application areas including batteries, supercapacitors, electrocatalytic reactors, and colloids. In the modeling of EDLs, a prominent knowledge gap has been the exclusion of van der Waals (vdW) and soft repulsive interactions in modified Poisson-Boltzmann (PB) theories. Although more short-ranged as compared to electrostatic interactions, we show here that vdW interactions can play an important role in determining the structure of the EDL via the formation of a Stern layer and in modulating the differential capacitance of an electrode in solution. To this end, we incorporate ion-ion and wall-ion vdW attraction and soft repulsion via a 12-6 Lennard-Jones (LJ) potential, resulting in a modified PB-LJ approach. The wall-ion LJ interactions were found to have a significant effect on the electrical potential and concentration profiles, especially close to the wall. However, ion-ion LJ interactions do not affect the EDL structure at low bulk ion concentrations (< 1 M). We also derive dimensionless numbers to quantify the impact of ion-ion and wall-ion LJ interactions on the EDL. Furthermore, in the pursuit of capturing ion-specific effects, we apply our model by considering various combinations of ions. We observe how varying parameters such as the electrolyte concentration and electrode potential affect the structure of the EDL due to the competition between ion-specific LJ and electrostatic interactions. Lastly, we show that the inclusion of vdW and soft repulsion interactions as well as hydration effects lead to a better qualitative agreement of the PB models with experimental double-layer differential capacitance data. Overall, the modified PB-LJ approach presented herein will lead to more accurate theoretical descriptions of EDLs in various application areas

Mucinous adenocarcinoma of gall bladder: a case report

Gall bladder carcinoma is the fifth most common malignancy of gastrointestinal tract. Mucinous carcinoma of gall bladder is very rare variant of gall bladder carcinoma. Only 20 cases of mucinous carcinoma reported till now. We report one such case of 55yr old female patient presented to our hospital with complaining of pain in right hypochondriac region and vomiting since, one month. Radiological examination revealed neoplastic thickening of gall bladder neck with cholelithiasis. Cholecystectomy was performed and specimen showed glistening grey white infiltrative firm solid mass at the neck of gall bladder. On microscopic examination showed mucinous adenocarcinoma. Tumour comprised of cystically dilated mucin filled glands. Tumour was seen infiltrating into muscle layer

Death due to sickle cell anemia: autopsy diagnosis

Background: Sickle cell disease (SCD) is well known and is the commonest hereditary hematological disorder which is associated with increased mortality and morbidity.  They are group of inherited haemoglobinopathies caused by the occurrence of hemoglobin S (Hbs) in homozygous or heterozygous form or in combinations of Hbs with another hemoglobin such as Hbsc or beta thalassaemia (Hbs-thal). Sickle cell syndromes are remarkable for their clinical heterogenecity including their presentations as sudden and unexpected death due to sickle cell crises. While doing autopsy in cases of deaths with no apparent cause and physical over activity medical officer must keep in mind the possibility of death due to vasoocclusive crisis in sickle cell disease. Aim of the study was to create awareness among the physicians and relatives / public and to minimize future unexpected death from complications or crisis from SCD.Methods: This is a retrospective study of 10 cases carried in the department of pathology, in tertiary care hospital and covers a period from January 2009 to December 2016. These cases were brought dead to the casualty with a history of sudden death. After post mortem examination, the specimens were sent for histopathological examination.Results: The record of 10 cases was reviewed. Out of our ten cases 7 were male and 3 were females. The youngest person was 17-year female and oldest was 65 years male. In clinical history 3 cases had complains of chest pain (30%), 3 others had complained of breathlessness (30%), 2 had history of unconsciousness (20%), one case had complained of abdominal pain (10%) and one case had a history of fall and injury (10%). Microscopic examination of each organ was carried out.  Organs like lungs, liver, spleen, kidneys, heart and brain showed wide spread congested vessels which were stuffed with RBC.Conclusions: We present this study to emphasize that sickle cell crisis is one of the cause of sudden unexplained death and highlight the importance of considering sickle cell disease as a cause of death in cases with no apparent cause

Multi-scale approach for modeling stability, aggregation, and network formation of nanoparticles suspended in aqueous solutions

Multi-scale computational framework to investigate interactions between bare and surfactant-coated nanoparticles in aqueous solutions beyond classical DLVO and aggregation theories

High risk of tuberculosis during infliximab therapy despite tuberculosis screening in inflammatory bowel disease patients in India

Background/Aims The data on the risk of tuberculosis (TB) reactivation with infliximab (IFX) in patients with inflammatory bowel disease (IBD) from TB endemic countries, like India, is limited. The risk of TB reactivation on IFX and its predictors in patients with IBD was assessed. Methods This retrospective review included consecutive patients with IBD who received IFX, and were on follow-up from January 2005 to November 2017. The data was recorded on age/disease duration, indications for IFX, screening for latent tuberculosis (LTB) before IFX, response to IFX, incidence and duration when TB developed after IFX, and type of TB (pulmonary [PTB]/extra-pulmonary [EPTB]/disseminated). Results Of 69 patients (22 ulcerative colitis/47 Crohn’s disease; mean age, 35.6±14.5 years; 50.7% males; median follow-up duration after IFX, 19 months [interquartile range, 5.5–48.7 months]), primary non-response at 8 weeks and secondary loss of response at 26 and 52 weeks were seen in 14.5%, 6% and 15% patients respectively. Prior to IFX, all patients were screened for LTB, 8 (11.6%) developed active TB (disseminated, 62.5%; EPTB, 25%; PTB, 12.5%) after a median of 19 weeks (interquartile range, 14.0–84.5 weeks) of IFX. Of these 8 patients’ none had LTB, even when 7 of 8 were additionally screened with contrast-enhanced chest tomography. Though not statistically significant, more patients with Crohn’s disease than ulcerative colitis (14.9% vs. 4.5%, P=0.21), and those with past history of TB (25% vs. 9.8%, P=0.21), developed TB. Age, gender, disease duration, or extraintestinal manifestations could not predict TB reactivation. Conclusions There is an extremely high rate of TB with IFX in Indian patients with IBD. Current screening techniques are ineffective and it is difficult to predict TB after IFX

Role of random biopsies in surveillance of dysplasia in ulcerative colitis patients with high risk of colorectal cancer

Background/AimsRecent data suggest that the incidence of ulcerative colitis (UC) related colorectal cancer (CRC) in India is similar to that of West. The optimum method for surveillance is still a debate. Surveillance with random biopsies has been the standard of care, but is a tedious process. We therefore undertook this study to assess the yield of random biopsy in dysplasia surveillance.MethodsBetween March 2014 and July 2015, patients of UC attending the Inflammatory Bowel Disease clinic at the All India Institute of Medical Sciences with high risk factors for CRC like duration of disease >15 years and pancolitis, family history of CRC, primary sclerosing cholangitis underwent surveillance colonoscopy for dysplasia. Four quadrant random biopsies at 10 cm intervals were taken (33 biopsies). Two pathologists examined specimens for dysplasia, and the yield of dysplasia was calculated.ResultsTwenty-eight patients were included. Twenty-six of these had pancolitis with a duration of disease greater than 15 years, and two patients had associated primary sclerosing cholangis. No patient had a family history of CRC. The mean age at onset of disease was 28.89±8.73 years and the duration of disease was 19.00±8.78 years. Eighteen patients (64.28%) were males. A total of 924 biopsies were taken. None of the biopsies revealed any evidence of dysplasia, and 7/924 (0.7%) were indefinite for dysplasia.ConclusionsRandom biopsy for surveillance in longstanding extensive colitis has a low yield for dysplasia and does not suffice for screening. Newer techniques such as chromoendoscopy-guided biopsies need greater adoption

Capture the growth kinetics of CVD growth of two-dimensional MoS 2

Understanding the microscopic mechanism is fundamental for function-oriented controlled chemical vapor deposition growth of two-dimensional (2D) materials. In this work, we reveal the growth kinetics of 2D MoS2 by capturing the nucleation seeds, evolving morphology, edge structure, and edge terminations at the atomic scale during chemical vapor deposition growth using the transmission electron microscopy and scanning transmission electron microscopy. The direct growth of few-layer and mono-layer MoS2 onto graphene-based transmission electron microscopy grids helped us to perform the subsequent transmission electron microscopy characterization without any solution-based transfer. Two seeding centers are observed: (i) Mo-oxysulfide (MoO x S2−y ) nanoparticles either in multi-shelled fullerene-like structures or as compact nanocrystals for the growth of fewer-layer MoS2; (ii) Mo-S atomic clusters. In the early stage growth, irregular polygons with two primary edge terminations, S-Mo Klein edges and Mo zigzag edges, appear approximately in equal numbers. The morphology evolves into a near-triangle shape in which Mo zigzag edges predominate. Results from density-functional theory calculations are consistent with the inferred growth kinetics, and thus support the growth mechanism we proposed. In general, the growth mechanisms found here should also be applicable in other 2D materials, such as MoSe2, WS2 and WSe2

Comparing cross-sectional and longitudinal approaches to Tuberculosis Patient Cost Surveys using Nepalese data.

The World Health Organization has supported the development of national tuberculosis (TB) patient cost surveys to quantify the socio-economic impact of TB in high-burden countries. However, methodological differences in study design (e.g. cross-sectional vs longitudinal) can generate different estimates making the design and impact evaluation of socioeconomic protection strategies difficult. The objective of the study was to compare the socio-economic impacts of TB estimated by applying cross-sectional or longitudinal data collections in Nepal. We analysed data from a longitudinal costing survey (patients interviewed at three-time points) conducted between April 2018 and October 2019. We calculated both mean and median costs from patients interviewed during the intensive (cross-sectional 1) and continuation phases of treatment (cross-sectional 2). We then compared costs, the prevalence of catastrophic costs and the socio-economic impact of TB generated by each approach. There were significant differences in the costs and social impacts calculated by each approach. The median total cost (intensive plus continuation phases) was significantly higher for the longitudinal compared to cross-sectional 2 (US$119.42 vs 91.63, P < 0.001). The prevalence of food insecurity, social exclusion and patients feeling poorer or much poorer were all significantly higher applying a longitudinal approach. In conclusion, the longitudinal design captured important aspects of costs and socioeconomic impacts which were missed by applying a cross-sectional approach. If a cross-sectional approach is applied due to resource constraints, our data suggest the start of the continuation phase is the optimal timing for a single interview. Further research to optimize methodologies to report patient incurred expenditure during TB diagnosis and treatment is needed